idnits 2.17.1 draft-ietf-extra-imap4rev2-26.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an Introduction section. ** There are 5 instances of too long lines in the document, the longest one being 6 characters in excess of 72. -- The draft header indicates that this document obsoletes RFC3501, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to contain a disclaimer for pre-RFC5378 work, but was first submitted on or after 10 November 2008. The disclaimer is usually necessary only for documents that revise or obsolete older RFCs, and that take significant amounts of text from those RFCs. If you can contact all authors of the source material and they are willing to grant the BCP78 rights to the IETF Trust, you can and should remove the disclaimer. Otherwise, the disclaimer is needed and you can ignore this comment. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (January 24, 2021) is 1185 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'IMAP2' is mentioned on line 7261, but not defined == Missing Reference: 'IMAP-OBSOLETE' is mentioned on line 7256, but not defined == Missing Reference: 'IMAP-COMPAT' is mentioned on line 7246, but not defined == Missing Reference: 'IMAP-HISTORICAL' is mentioned on line 7251, but not defined == Missing Reference: 'RFC-822' is mentioned on line 7265, but not defined ** Obsolete undefined reference: RFC 822 (Obsoleted by RFC 2822) == Missing Reference: 'IMAP-MODEL' is mentioned on line 7195, but not defined == Missing Reference: 'IMAP-DISC' is mentioned on line 7184, but not defined == Missing Reference: 'RFC3503' is mentioned on line 7161, but not defined == Missing Reference: 'IMAP-KEYWORDS-REG' is mentioned on line 7224, but not defined == Missing Reference: 'SMTP' is mentioned on line 7205, but not defined == Missing Reference: 'RFC7888' is mentioned on line 7180, but not defined -- Looks like a reference, but probably isn't: '1' on line 906 == Missing Reference: 'IMAP-URL' is mentioned on line 7219, but not defined == Missing Reference: 'TLS' is mentioned on line 1219, but not defined == Missing Reference: 'CERT-555316' is mentioned on line 7147, but not defined == Missing Reference: 'UIDVALIDITY 3857529045' is mentioned on line 5864, but not defined == Missing Reference: 'UIDNEXT 4392' is mentioned on line 1785, but not defined == Missing Reference: 'RFC2193' is mentioned on line 7152, but not defined == Missing Reference: 'RFC3348' is mentioned on line 7556, but not defined ** Obsolete undefined reference: RFC 3348 (Obsoleted by RFC 5258) == Missing Reference: 'RFC4314' is mentioned on line 7212, but not defined == Missing Reference: 'RFC3501' is mentioned on line 7242, but not defined ** Obsolete undefined reference: RFC 3501 (Obsoleted by RFC 9051) == Missing Reference: 'UIDNEXT 2' is mentioned on line 3320, but not defined == Missing Reference: 'UIDVALIDITY 1' is mentioned on line 3392, but not defined == Missing Reference: 'CHARSET-REG' is mentioned on line 7234, but not defined == Missing Reference: 'IMAP-I18N' is mentioned on line 7189, but not defined == Missing Reference: 'HEADER' is mentioned on line 5882, but not defined == Missing Reference: 'BADCHARSET UTF-8' is mentioned on line 3972, but not defined == Missing Reference: 'UID' is mentioned on line 4395, but not defined == Missing Reference: 'RFC2087' is mentioned on line 7216, but not defined ** Obsolete undefined reference: RFC 2087 (Obsoleted by RFC 9208) == Missing Reference: 'IMAP-MAILBOX-NAME-ATTRS-REG' is mentioned on line 7229, but not defined == Missing Reference: 'READ-WRITE' is mentioned on line 5866, but not defined == Missing Reference: 'RFC4422' is mentioned on line 6225, but not defined == Missing Reference: 'IMAP4' is mentioned on line 6310, but not defined == Missing Reference: 'IMAP-TLS' is mentioned on line 7269, but not defined == Missing Reference: 'RFC6186' is mentioned on line 7175, but not defined == Missing Reference: 'RFCXXXX' is mentioned on line 6974, but not defined == Missing Reference: 'RFC5465' is mentioned on line 7171, but not defined == Missing Reference: 'RFC5256' is mentioned on line 7166, but not defined == Missing Reference: 'IMAP-UTF-8' is mentioned on line 7288, but not defined == Missing Reference: 'RFC3516' is mentioned on line 7384, but not defined ** Downref: Normative reference to an Informational RFC: RFC 2152 (ref. 'UTF-7') ** Downref: Normative reference to an Informational RFC: RFC 2683 (ref. 'IMAP-IMPLEMENTATION') ** Downref: Normative reference to an Informational RFC: RFC 2180 (ref. 'IMAP-MULTIACCESS') Summary: 9 errors (**), 0 flaws (~~), 41 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Melnikov, Ed. 3 Internet-Draft Isode Ltd 4 Obsoletes: 3501 (if approved) B. Leiba, Ed. 5 Intended status: Standards Track Futurewei Technologies 6 Expires: July 28, 2021 January 24, 2021 8 Internet Message Access Protocol (IMAP) - Version 4rev2 9 draft-ietf-extra-imap4rev2-26 11 Abstract 13 The Internet Message Access Protocol, Version 4rev2 (IMAP4rev2) 14 allows a client to access and manipulate electronic mail messages on 15 a server. IMAP4rev2 permits manipulation of mailboxes (remote 16 message folders) in a way that is functionally equivalent to local 17 folders. IMAP4rev2 also provides the capability for an offline 18 client to resynchronize with the server. 20 IMAP4rev2 includes operations for creating, deleting, and renaming 21 mailboxes, checking for new messages, permanently removing messages, 22 setting and clearing flags, RFC 5322, RFC 2045 and RFC 2231 parsing, 23 searching, and selective fetching of message attributes, texts, and 24 portions thereof. Messages in IMAP4rev2 are accessed by the use of 25 numbers. These numbers are either message sequence numbers or unique 26 identifiers. 28 IMAP4rev2 does not specify a means of posting mail; this function is 29 handled by a mail submission protocol such as the one specified in 30 RFC 6409. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on July 28, 2021. 49 Copyright Notice 51 Copyright (c) 2021 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 This document may contain material from IETF Documents or IETF 65 Contributions published or made publicly available before November 66 10, 2008. The person(s) controlling the copyright in some of this 67 material may not have granted the IETF Trust the right to allow 68 modifications of such material outside the IETF Standards Process. 69 Without obtaining an adequate license from the person(s) controlling 70 the copyright in such materials, this document may not be modified 71 outside the IETF Standards Process, and derivative works of it may 72 not be created outside the IETF Standards Process, except to format 73 it for publication as an RFC or to translate it into languages other 74 than English. 76 Table of Contents 78 1. How to Read This Document . . . . . . . . . . . . . . . . . . 5 79 1.1. Organization of This Document . . . . . . . . . . . . . . 5 80 1.2. Conventions Used in This Document . . . . . . . . . . . . 5 81 1.3. Special Notes to Implementors . . . . . . . . . . . . . . 6 82 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 83 2.1. Link Level . . . . . . . . . . . . . . . . . . . . . . . 7 84 2.2. Commands and Responses . . . . . . . . . . . . . . . . . 7 85 2.2.1. Client Protocol Sender and Server Protocol Receiver . 7 86 2.2.2. Server Protocol Sender and Client Protocol Receiver . 8 87 2.3. Message Attributes . . . . . . . . . . . . . . . . . . . 9 88 2.3.1. Message Numbers . . . . . . . . . . . . . . . . . . . 9 89 2.3.2. Flags Message Attribute . . . . . . . . . . . . . . . 12 90 2.3.3. Internal Date Message Attribute . . . . . . . . . . . 14 91 2.3.4. [RFC-5322] Size Message Attribute . . . . . . . . . . 14 92 2.3.5. Envelope Structure Message Attribute . . . . . . . . 14 93 2.3.6. Body Structure Message Attribute . . . . . . . . . . 14 94 2.4. Message Texts . . . . . . . . . . . . . . . . . . . . . . 14 95 3. State and Flow Diagram . . . . . . . . . . . . . . . . . . . 14 96 3.1. Not Authenticated State . . . . . . . . . . . . . . . . . 15 97 3.2. Authenticated State . . . . . . . . . . . . . . . . . . . 15 98 3.3. Selected State . . . . . . . . . . . . . . . . . . . . . 15 99 3.4. Logout State . . . . . . . . . . . . . . . . . . . . . . 15 100 4. Data Formats . . . . . . . . . . . . . . . . . . . . . . . . 17 101 4.1. Atom . . . . . . . . . . . . . . . . . . . . . . . . . . 17 102 4.1.1. Sequence set and UID set . . . . . . . . . . . . . . 17 103 4.2. Number . . . . . . . . . . . . . . . . . . . . . . . . . 17 104 4.3. String . . . . . . . . . . . . . . . . . . . . . . . . . 17 105 4.3.1. 8-bit and Binary Strings . . . . . . . . . . . . . . 18 106 4.4. Parenthesized List . . . . . . . . . . . . . . . . . . . 19 107 4.5. NIL . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 108 5. Operational Considerations . . . . . . . . . . . . . . . . . 20 109 5.1. Mailbox Naming . . . . . . . . . . . . . . . . . . . . . 20 110 5.1.1. Mailbox Hierarchy Naming . . . . . . . . . . . . . . 21 111 5.1.2. Namespaces . . . . . . . . . . . . . . . . . . . . . 21 112 5.2. Mailbox Size and Message Status Updates . . . . . . . . . 23 113 5.3. Response when no Command in Progress . . . . . . . . . . 23 114 5.4. Autologout Timer . . . . . . . . . . . . . . . . . . . . 23 115 5.5. Multiple Commands in Progress (Command Pipelining) . . . 24 116 6. Client Commands . . . . . . . . . . . . . . . . . . . . . . . 25 117 6.1. Client Commands - Any State . . . . . . . . . . . . . . . 26 118 6.1.1. CAPABILITY Command . . . . . . . . . . . . . . . . . 26 119 6.1.2. NOOP Command . . . . . . . . . . . . . . . . . . . . 27 120 6.1.3. LOGOUT Command . . . . . . . . . . . . . . . . . . . 27 121 6.2. Client Commands - Not Authenticated State . . . . . . . . 28 122 6.2.1. STARTTLS Command . . . . . . . . . . . . . . . . . . 28 123 6.2.2. AUTHENTICATE Command . . . . . . . . . . . . . . . . 30 124 6.2.3. LOGIN Command . . . . . . . . . . . . . . . . . . . . 33 125 6.3. Client Commands - Authenticated State . . . . . . . . . . 33 126 6.3.1. ENABLE Command . . . . . . . . . . . . . . . . . . . 34 127 6.3.2. SELECT Command . . . . . . . . . . . . . . . . . . . 36 128 6.3.3. EXAMINE Command . . . . . . . . . . . . . . . . . . . 38 129 6.3.4. CREATE Command . . . . . . . . . . . . . . . . . . . 39 130 6.3.5. DELETE Command . . . . . . . . . . . . . . . . . . . 40 131 6.3.6. RENAME Command . . . . . . . . . . . . . . . . . . . 42 132 6.3.7. SUBSCRIBE Command . . . . . . . . . . . . . . . . . . 44 133 6.3.8. UNSUBSCRIBE Command . . . . . . . . . . . . . . . . . 45 134 6.3.9. LIST Command . . . . . . . . . . . . . . . . . . . . 45 135 6.3.10. NAMESPACE Command . . . . . . . . . . . . . . . . . . 64 136 6.3.11. STATUS Command . . . . . . . . . . . . . . . . . . . 68 137 6.3.12. APPEND Command . . . . . . . . . . . . . . . . . . . 69 138 6.3.13. IDLE Command . . . . . . . . . . . . . . . . . . . . 72 139 6.4. Client Commands - Selected State . . . . . . . . . . . . 74 140 6.4.1. CLOSE Command . . . . . . . . . . . . . . . . . . . . 75 141 6.4.2. UNSELECT Command . . . . . . . . . . . . . . . . . . 75 142 6.4.3. EXPUNGE Command . . . . . . . . . . . . . . . . . . . 76 143 6.4.4. SEARCH Command . . . . . . . . . . . . . . . . . . . 76 144 6.4.5. FETCH Command . . . . . . . . . . . . . . . . . . . . 88 145 6.4.6. STORE Command . . . . . . . . . . . . . . . . . . . . 93 146 6.4.7. COPY Command . . . . . . . . . . . . . . . . . . . . 94 147 6.4.8. MOVE Command . . . . . . . . . . . . . . . . . . . . 95 148 6.4.9. UID Command . . . . . . . . . . . . . . . . . . . . . 97 149 6.5. Client Commands - Experimental/Expansion . . . . . . . . 99 150 7. Server Responses . . . . . . . . . . . . . . . . . . . . . . 99 151 7.1. Server Responses - Generic Status Responses . . . . . . . 100 152 7.1.1. OK Response . . . . . . . . . . . . . . . . . . . . . 108 153 7.1.2. NO Response . . . . . . . . . . . . . . . . . . . . . 109 154 7.1.3. BAD Response . . . . . . . . . . . . . . . . . . . . 109 155 7.1.4. PREAUTH Response . . . . . . . . . . . . . . . . . . 110 156 7.1.5. BYE Response . . . . . . . . . . . . . . . . . . . . 110 157 7.2. Server Responses - Server Status . . . . . . . . . . . . 111 158 7.2.1. ENABLED Response . . . . . . . . . . . . . . . . . . 111 159 7.2.2. CAPABILITY Response . . . . . . . . . . . . . . . . . 111 160 7.3. Server Responses - Mailbox Status . . . . . . . . . . . . 112 161 7.3.1. LIST Response . . . . . . . . . . . . . . . . . . . . 112 162 7.3.2. NAMESPACE Response . . . . . . . . . . . . . . . . . 116 163 7.3.3. STATUS Response . . . . . . . . . . . . . . . . . . . 117 164 7.3.4. ESEARCH Response . . . . . . . . . . . . . . . . . . 117 165 7.3.5. FLAGS Response . . . . . . . . . . . . . . . . . . . 117 166 7.4. Server Responses - Mailbox Size . . . . . . . . . . . . . 118 167 7.4.1. EXISTS Response . . . . . . . . . . . . . . . . . . . 118 168 7.5. Server Responses - Message Status . . . . . . . . . . . . 118 169 7.5.1. EXPUNGE Response . . . . . . . . . . . . . . . . . . 118 170 7.5.2. FETCH Response . . . . . . . . . . . . . . . . . . . 119 171 7.6. Server Responses - Command Continuation Request . . . . . 125 172 8. Sample IMAP4rev2 connection . . . . . . . . . . . . . . . . . 126 173 9. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 127 174 10. Author's Note . . . . . . . . . . . . . . . . . . . . . . . . 145 175 11. Security Considerations . . . . . . . . . . . . . . . . . . . 146 176 11.1. TLS related Security Considerations . . . . . . . . . . 146 177 11.2. STARTTLS command versa use of Implicit TLS port . . . . 146 178 11.3. Client handling of unsolicited responses not suitable 179 for the current connection state . . . . . . . . . . . . 147 180 11.4. COPYUID and APPENDUID response codes . . . . . . . . . . 147 181 11.5. LIST command and Other Users' namespace . . . . . . . . 148 182 11.6. Other Security Considerations . . . . . . . . . . . . . 148 183 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 149 184 12.1. Updates to IMAP4 Capabilities registry . . . . . . . . . 149 185 12.2. GSSAPI/SASL service name . . . . . . . . . . . . . . . . 149 186 12.3. LIST Selection Options, LIST Return Options, LIST 187 extended data items . . . . . . . . . . . . . . . . . . 150 188 12.4. IMAP Mailbox Name Attributes and IMAP Response Codes . . 150 189 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 150 190 13.1. Normative References . . . . . . . . . . . . . . . . . . 150 191 13.2. Informative References (related protocols) . . . . . . . 153 192 13.3. Informative References (historical aspects of IMAP and 193 related protocols) . . . . . . . . . . . . . . . . . . . 156 194 Appendix A. Backward compatibility with IMAP4rev1 . . . . . . . 156 195 A.1. Mailbox International Naming Convention for compatibility 196 with IMAP4rev1 . . . . . . . . . . . . . . . . . . . . . 157 197 Appendix B. Backward compatibility with BINARY extension . . . . 159 198 Appendix C. Backward compatibility with LIST-EXTENDED extension 159 199 Appendix D. 63 bit body part and message sizes . . . . . . . . . 159 200 Appendix E. Changes from RFC 3501 / IMAP4rev1 . . . . . . . . . 159 201 Appendix F. Other Recommended IMAP Extensions . . . . . . . . . 161 202 Appendix G. Acknowledgement . . . . . . . . . . . . . . . . . . 162 203 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 204 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 168 206 1. How to Read This Document 208 1.1. Organization of This Document 210 This document is written from the point of view of the implementor of 211 an IMAP4rev2 client or server. Beyond the protocol overview in 212 section 2, it is not optimized for someone trying to understand the 213 operation of the protocol. The material in sections 3 through 5 214 provides the general context and definitions with which IMAP4rev2 215 operates. 217 Sections 6, 7, and 9 describe the IMAP commands, responses, and 218 syntax, respectively. The relationships among these are such that it 219 is almost impossible to understand any of them separately. In 220 particular, do not attempt to deduce command syntax from the command 221 section alone; instead refer to the Formal Syntax (Section 9). 223 1.2. Conventions Used in This Document 225 "Conventions" are basic principles or procedures. Document 226 conventions are noted in this section. 228 In examples, "C:" and "S:" indicate lines sent by the client and 229 server respectively. Note that each line includes the terminating 230 CRLF. 232 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 233 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 234 "OPTIONAL" in this document are to be interpreted as described in BCP 235 14 [RFC2119] [RFC8174] when, and only when, they appear in all 236 capitals, as shown here. 238 The word "can" (not "may") is used to refer to a possible 239 circumstance or situation, as opposed to an optional facility of the 240 protocol. 242 "User" is used to refer to a human user, whereas "client" refers to 243 the software being run by the user. 245 "Connection" refers to the entire sequence of client/server 246 interaction from the initial establishment of the network connection 247 until its termination. 249 "Session" refers to the sequence of client/server interaction from 250 the time that a mailbox is selected (SELECT or EXAMINE command) until 251 the time that selection ends (SELECT or EXAMINE of another mailbox, 252 CLOSE command, UNSELECT command, or connection termination). 254 The term "Implicit TLS" refers to the automatic negotiation of TLS 255 whenever a TCP connection is made on a particular TCP port that is 256 used exclusively by that server for TLS connections. The term 257 "Implicit TLS" is intended to contrast with the use of STARTTLS 258 command in IMAP that is used by the client and the server to 259 explicitly negotiate TLS on an established cleartext TCP connection. 261 Characters are 8-bit UTF-8 (of which 7-bit US-ASCII is a subset) 262 unless otherwise specified. Other character sets are indicated using 263 a "CHARSET", as described in [MIME-IMT] and defined in [CHARSET]. 264 CHARSETs have important additional semantics in addition to defining 265 character set; refer to these documents for more detail. 267 There are several protocol conventions in IMAP. These refer to 268 aspects of the specification which are not strictly part of the IMAP 269 protocol, but reflect generally-accepted practice. Implementations 270 need to be aware of these conventions, and avoid conflicts whether or 271 not they implement the convention. For example, "&" may not be used 272 as a hierarchy delimiter since it conflicts with the Mailbox 273 International Naming Convention, and other uses of "&" in mailbox 274 names are impacted as well. 276 1.3. Special Notes to Implementors 278 Implementors of the IMAP protocol are strongly encouraged to read the 279 IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in 280 conjunction with this document, to help understand the intricacies of 281 this protocol and how best to build an interoperable product. 283 IMAP4rev2 is designed to be upwards compatible from the IMAP4rev1, 284 the [IMAP2] and unpublished IMAP2bis protocols. IMAP4rev2 is largely 285 compatible with the IMAP4rev1 protocol described in RFC 3501 and the 286 IMAP4 protocol described in RFC 1730; the exception being in certain 287 facilities added in RFC 1730 and RFC 3501 that proved problematic and 288 were subsequently removed or replaced by better alternatives. In the 289 course of the evolution of IMAP4rev2, some aspects in the earlier 290 protocols have become obsolete. Obsolete commands, responses, and 291 data formats which an IMAP4rev2 implementation can encounter when 292 used with an earlier implementation are described in Appendix E, 293 Appendix A and [IMAP-OBSOLETE]. IMAP4rev2 supports 63bit body part 294 and message sizes. IMAP4rev2 compatibility with BINARY and LIST- 295 EXTENDED IMAP extensions are described in Appendix B and Appendix C 296 respectively. 298 Other compatibility issues with IMAP2bis, the most common variant of 299 the earlier protocol, are discussed in [IMAP-COMPAT]. A full 300 discussion of compatibility issues with rare (and presumed extinct) 301 variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is 302 primarily of historical interest. 304 IMAP was originally developed for the older [RFC-822] standard, and 305 as a consequence several fetch items in IMAP incorporate "RFC822" in 306 their name. In all cases, "RFC822" should be interpreted as a 307 reference to the updated [RFC-5322] standard. 309 2. Protocol Overview 311 2.1. Link Level 313 The IMAP4rev2 protocol assumes a reliable data stream such as that 314 provided by TCP. When TCP is used, an IMAP4rev2 server listens on 315 port 143 (cleartext port) or port 993 (Implicit TLS port). 317 2.2. Commands and Responses 319 An IMAP4rev2 connection consists of the establishment of a client/ 320 server network connection, an initial greeting from the server, and 321 client/server interactions. These client/server interactions consist 322 of a client command, server data, and a server completion result 323 response. 325 All interactions transmitted by client and server are in the form of 326 lines, that is, strings that end with a CRLF. The protocol receiver 327 of an IMAP4rev2 client or server is either reading a line, or is 328 reading a sequence of octets with a known count followed by a line. 330 2.2.1. Client Protocol Sender and Server Protocol Receiver 332 The client command begins an operation. Each client command is 333 prefixed with an identifier (typically a short alphanumeric string, 334 e.g., A0001, A0002, etc.) called a "tag". A different tag is 335 generated by the client for each command. More formally: the client 336 SHOULD generate a unique tag for every command, but a server MUST 337 accept tag reuse. 339 Clients MUST follow the syntax outlined in this specification 340 strictly. It is a syntax error to send a command with missing or 341 extraneous spaces or arguments. 343 There are two cases in which a line from the client does not 344 represent a complete command. In one case, a command argument is 345 quoted with an octet count (see the description of literal in 346 Section 4.3); in the other case, the command arguments require server 347 feedback (see the AUTHENTICATE command in Section 6.2.2). In either 348 case, the server sends a command continuation request response if it 349 is ready for the octets (if appropriate) and the remainder of the 350 command. This response is prefixed with the token "+". 352 Note: If instead, the server detected an error in the command, it 353 sends a BAD completion response with a tag matching the command 354 (as described below) to reject the command and prevent the client 355 from sending any more of the command. 357 It is also possible for the server to send a completion response 358 for some other command (if multiple commands are in progress), or 359 untagged data. In either case, the command continuation request 360 is still pending; the client takes the appropriate action for the 361 response, and reads another response from the server. In all 362 cases, the client MUST send a complete command (including 363 receiving all command continuation request responses and command 364 continuations for the command) before initiating a new command. 366 The protocol receiver of an IMAP4rev2 server reads a command line 367 from the client, parses the command and its arguments, and transmits 368 server data and a server command completion result response. 370 2.2.2. Server Protocol Sender and Client Protocol Receiver 372 Data transmitted by the server to the client and status responses 373 that do not indicate command completion are prefixed with the token 374 "*", and are called untagged responses. 376 Server data MAY be sent as a result of a client command, or MAY be 377 sent unilaterally by the server. There is no syntactic difference 378 between server data that resulted from a specific command and server 379 data that were sent unilaterally. 381 The server completion result response indicates the success or 382 failure of the operation. It is tagged with the same tag as the 383 client command which began the operation. Thus, if more than one 384 command is in progress, the tag in a server completion response 385 identifies the command to which the response applies. There are 386 three possible server completion responses: OK (indicating success), 387 NO (indicating failure), or BAD (indicating a protocol error such as 388 unrecognized command or command syntax error). 390 Servers SHOULD enforce the syntax outlined in this specification 391 strictly. Any client command with a protocol syntax error, including 392 (but not limited to) missing or extraneous spaces or arguments, 393 SHOULD be rejected, and the client given a BAD server completion 394 response. 396 The protocol receiver of an IMAP4rev2 client reads a response line 397 from the server. It then takes action on the response based upon the 398 first token of the response, which can be a tag, a "*", or a "+". 400 A client MUST be prepared to accept any server response at all times. 401 This includes server data that was not requested. Server data SHOULD 402 be remembered (cached), so that the client can reference its 403 remembered copy rather than sending a command to the server to 404 request the data. In the case of certain server data, the data MUST 405 be remembered, as specified elsewhere in this document. 407 This topic is discussed in greater detail in the Server Responses 408 section. 410 2.3. Message Attributes 412 In addition to message text, each message has several attributes 413 associated with it. These attributes can be retrieved individually 414 or in conjunction with other attributes or message texts. 416 2.3.1. Message Numbers 418 Messages in IMAP4rev2 are accessed by one of two numbers; the unique 419 identifier or the message sequence number. 421 2.3.1.1. Unique Identifier (UID) Message Attribute 423 A UID is an unsigned non-zero 32-bit value assigned to each message, 424 which when used with the unique identifier validity value (see below) 425 forms a 64-bit value that MUST NOT refer to any other message in the 426 mailbox or any subsequent mailbox with the same name forever. Unique 427 identifiers are assigned in a strictly ascending fashion in the 428 mailbox; as each message is added to the mailbox it is assigned a 429 higher UID than the message(s) which were added previously. Unlike 430 message sequence numbers, unique identifiers are not necessarily 431 contiguous. 433 The unique identifier of a message MUST NOT change during the 434 session, and SHOULD NOT change between sessions. Any change of 435 unique identifiers between sessions MUST be detectable using the 436 UIDVALIDITY mechanism discussed below. Persistent unique identifiers 437 are required for a client to resynchronize its state from a previous 438 session with the server (e.g., disconnected or offline access clients 439 [IMAP-MODEL]); this is discussed further in [IMAP-DISC]. 441 Associated with every mailbox are two 32-bit unsigned non-zero values 442 which aid in unique identifier handling: the next unique identifier 443 value (UIDNEXT) and the unique identifier validity value 444 (UIDVALIDITY). 446 The next unique identifier value is the predicted value that will be 447 assigned to a new message in the mailbox. Unless the unique 448 identifier validity also changes (see below), the next unique 449 identifier value MUST have the following two characteristics. First, 450 the next unique identifier value MUST NOT change unless new messages 451 are added to the mailbox; and second, the next unique identifier 452 value MUST change whenever new messages are added to the mailbox, 453 even if those new messages are subsequently expunged. 455 Note: The next unique identifier value is intended to provide a 456 means for a client to determine whether any messages have been 457 delivered to the mailbox since the previous time it checked this 458 value. It is not intended to provide any guarantee that any 459 message will have this unique identifier. A client can only 460 assume, at the time that it obtains the next unique identifier 461 value, that messages arriving after that time will have a UID 462 greater than or equal to that value. 464 The unique identifier validity value is sent in a UIDVALIDITY 465 response code in an OK untagged response at mailbox selection time. 466 If unique identifiers from an earlier session fail to persist in this 467 session, the unique identifier validity value MUST be greater than 468 the one used in the earlier session. A good UIDVALIDITY value to use 469 is a 32-bit representation of the current date/time when the value is 470 assigned: this ensures that the value is unique and always increases. 471 Another possible alternative is a global counter that gets 472 incremented every time a mailbox is created. 474 Note: Ideally, unique identifiers SHOULD persist at all times. 475 Although this specification recognizes that failure to persist can 476 be unavoidable in certain server environments, it strongly 477 encourages message store implementation techniques that avoid this 478 problem. For example: 480 1. Unique identifiers MUST be strictly ascending in the mailbox 481 at all times. If the physical message store is re-ordered by 482 a non-IMAP agent, this requires that the unique identifiers in 483 the mailbox be regenerated, since the former unique 484 identifiers are no longer strictly ascending as a result of 485 the re-ordering. 487 2. If the message store has no mechanism to store unique 488 identifiers, it must regenerate unique identifiers at each 489 session, and each session must have a unique UIDVALIDITY 490 value. 492 3. If the mailbox is deleted/renamed and a new mailbox with the 493 same name is created at a later date, the server must either 494 keep track of unique identifiers from the previous instance of 495 the mailbox, or it must assign a new UIDVALIDITY value to the 496 new instance of the mailbox. 498 4. The combination of mailbox name, UIDVALIDITY, and UID must 499 refer to a single immutable (or expunged) message on that 500 server forever. In particular, the internal date, [RFC-5322] 501 size, envelope, body structure, and message texts (all 502 BODY[...] fetch data items) must never change. This does not 503 include message numbers, nor does it include attributes that 504 can be set by a STORE command (e.g., FLAGS). When a message 505 is expunged, its UID MUST NOT be reused under the same 506 UIDVALIDITY value. 508 2.3.1.2. Message Sequence Number Message Attribute 510 A Message Sequence Number is a relative position from 1 to the number 511 of messages in the mailbox. This position MUST be ordered by 512 ascending unique identifier. As each new message is added, it is 513 assigned a message sequence number that is 1 higher than the number 514 of messages in the mailbox before that new message was added. 516 Message sequence numbers can be reassigned during the session. For 517 example, when a message is permanently removed (expunged) from the 518 mailbox, the message sequence number for all subsequent messages is 519 decremented. The number of messages in the mailbox is also 520 decremented. Similarly, a new message can be assigned a message 521 sequence number that was once held by some other message prior to an 522 expunge. 524 In addition to accessing messages by relative position in the 525 mailbox, message sequence numbers can be used in mathematical 526 calculations. For example, if an untagged "11 EXISTS" is received, 527 and previously an untagged "8 EXISTS" was received, three new 528 messages have arrived with message sequence numbers of 9, 10, and 11. 529 Another example, if message 287 in a 523 message mailbox has UID 530 12345, there are exactly 286 messages which have lesser UIDs and 236 531 messages which have greater UIDs. 533 2.3.2. Flags Message Attribute 535 A message has associated with it a list of zero or more named tokens, 536 known as "flags". A flag is set by its addition to this list, and is 537 cleared by its removal. There are two types of flags in IMAP4rev2: 538 system flags, and keywords. A flag of either type can also be 539 permanent or session-only. 541 A system flag is a flag name that is pre-defined in this 542 specification and begins with "\". Certain system flags (\Deleted 543 and \Seen) have special semantics described elsewhere in this 544 document. The currently-defined system flags are: 546 \Seen Message has been read 548 \Answered Message has been answered 550 \Flagged Message is "flagged" for urgent/special attention 552 \Deleted Message is "deleted" for removal by later EXPUNGE 554 \Draft Message has not completed composition (marked as a draft). 556 \Recent This flag was in use in IMAP4rev1 and is now deprecated. 558 A keyword is defined by the server implementation. Keywords do not 559 begin with "\". Servers MAY permit the client to define new keywords 560 in the mailbox (see the description of the PERMANENTFLAGS response 561 code for more information). Some keywords that start with "$" are 562 also defined in this specification. 564 This document defines several keywords that were not originally 565 defined in RFC 3501, but which were found to be useful by client 566 implementations. These keywords SHOULD be supported (i.e. allowed in 567 SEARCH, allowed and preserved in APPEND, COPY, MOVE commands) by 568 server implementations: 570 $Forwarded Message has been forwarded to another email address, 571 embedded within or attached to a new message. An email client 572 sets this keyword when it successfully forwards the message to 573 another email address. Typical usage of this keyword is to show a 574 different (or additional) icon for a message that has been 575 forwarded. Once set, the flag SHOULD NOT be cleared. 577 $MDNSent Message Disposition Notification [RFC8098] was generated 578 and sent for this message. See [RFC3503] for more details on how 579 this keyword is used. 581 $Junk The user (or a delivery agent on behalf of the user) may 582 choose to mark a message as definitely containing junk ($Junk; see 583 also the related keyword $NotJunk). The $Junk keyword can be used 584 to mark (and potentially move/delete messages later), group or 585 hide undesirable messages. See [IMAP-KEYWORDS-REG] for more 586 information. 588 $NotJunk The user (or a delivery agent on behalf of the user) may 589 choose to mark a message as definitely not containing junk 590 ($NotJunk; see also the related keyword $Junk). The $NotJunk 591 keyword can be used to mark, group or show messages that the user 592 wants to see. See [IMAP-KEYWORDS-REG] for more information. 594 $Phishing The $Phishing keyword can be used by a delivery agent to 595 mark a message as highly likely to be a phishing email. An email 596 that's determined to be a phishing email by the delivery agent 597 should also be considered a junk email and have the appropriate 598 junk filtering applied, including setting the $Junk flag and 599 placing in the \Junk special-use mailbox (see Section 7.3.1) if 600 available. 601 If both the $Phishing flag and the $Junk flag are set, the user 602 agent should display an additional warning message to the user. 603 Additionally the user agent may display a warning when clicking on 604 any hyperlinks within the message. 605 The requirement for both $Phishing and $Junk to be set before a 606 user agent displays a warning is for better backwards 607 compatibility with existing clients that understand the $Junk flag 608 but not the $Phishing flag. This so that when an unextended 609 client removes the $Junk flag, an extended client will also show 610 the correct state. See [IMAP-KEYWORDS-REG] for more information. 612 $Junk and $NotJunk are mutually exclusive. If more than one of them 613 is set for a message, the client MUST treat this as if none of them 614 is set and SHOULD unset both of them on the IMAP server. 616 Other registered keywords can be found in the "IMAP and JMAP 617 Keywords" registry [IMAP-KEYWORDS-REG]. New keywords SHOULD be 618 registered in this registry using the procedure specified in 619 [RFC5788]. 621 A flag can be permanent or session-only on a per-flag basis. 622 Permanent flags are those which the client can add or remove from the 623 message flags permanently; that is, concurrent and subsequent 624 sessions will see any change in permanent flags. Changes to session 625 flags are valid only in that session. 627 2.3.3. Internal Date Message Attribute 629 An Internal Date message attribute is the internal date and time of 630 the message on the server. This is not the date and time in the 631 [RFC-5322] header, but rather a date and time which reflects when the 632 message was received. In the case of messages delivered via [SMTP], 633 this is the date and time of final delivery of the message as defined 634 by [SMTP]. In the case of messages delivered by the IMAP4rev2 COPY 635 or MOVE command, this SHOULD be the internal date and time of the 636 source message. In the case of messages delivered by the IMAP4rev2 637 APPEND command, this SHOULD be the date and time as specified in the 638 APPEND command description. All other cases are implementation 639 defined. 641 2.3.4. [RFC-5322] Size Message Attribute 643 An RFC 5322 size is the number of octets in the message, as expressed 644 in [RFC-5322] format. 646 2.3.5. Envelope Structure Message Attribute 648 An Envelope Structure is a parsed representation of the [RFC-5322] 649 header of the message. Note that the IMAP Envelope structure is not 650 the same as an [SMTP] envelope. 652 2.3.6. Body Structure Message Attribute 654 A Body Structure is a parsed representation of the [MIME-IMB] body 655 structure information of the message. 657 2.4. Message Texts 659 In addition to being able to fetch the full [RFC-5322] text of a 660 message, IMAP4rev2 permits the fetching of portions of the full 661 message text. Specifically, it is possible to fetch the [RFC-5322] 662 message header, [RFC-5322] message body, a [MIME-IMB] body part, or a 663 [MIME-IMB] header. 665 3. State and Flow Diagram 667 Once the connection between client and server is established, an 668 IMAP4rev2 connection is in one of four states. The initial state is 669 identified in the server greeting. Most commands are only valid in 670 certain states. It is a protocol error for the client to attempt a 671 command while the connection is in an inappropriate state, and the 672 server will respond with a BAD or NO (depending upon server 673 implementation) command completion result. 675 3.1. Not Authenticated State 677 In the not authenticated state, the client MUST supply authentication 678 credentials before most commands will be permitted. This state is 679 entered when a connection starts unless the connection has been pre- 680 authenticated. 682 3.2. Authenticated State 684 In the authenticated state, the client is authenticated and MUST 685 select a mailbox to access before commands that affect messages will 686 be permitted. This state is entered when a pre-authenticated 687 connection starts, when acceptable authentication credentials have 688 been provided, after an error in selecting a mailbox, or after a 689 successful CLOSE command. 691 3.3. Selected State 693 In a selected state, a mailbox has been selected to access. This 694 state is entered when a mailbox has been successfully selected. 696 3.4. Logout State 698 In the logout state, the connection is being terminated. This state 699 can be entered as a result of a client request (via the LOGOUT 700 command) or by unilateral action on the part of either the client or 701 server. 703 If the client requests the logout state, the server MUST send an 704 untagged BYE response and a tagged OK response to the LOGOUT command 705 before the server closes the connection; and the client MUST read the 706 tagged OK response to the LOGOUT command before the client closes the 707 connection. 709 A server SHOULD NOT unilaterally close the connection without sending 710 an untagged BYE response that contains the reason for having done so. 711 A client SHOULD NOT unilaterally close the connection, and instead 712 SHOULD issue a LOGOUT command. If the server detects that the client 713 has unilaterally closed the connection, the server MAY omit the 714 untagged BYE response and simply close its connection. 716 +----------------------+ 717 |connection established| 718 +----------------------+ 719 || 720 \/ 721 +--------------------------------------+ 722 | server greeting | 723 +--------------------------------------+ 724 || (1) || (2) || (3) 725 \/ || || 726 +-----------------+ || || 727 |Not Authenticated| || || 728 +-----------------+ || || 729 || (7) || (4) || || 730 || \/ \/ || 731 || +----------------+ || 732 || | Authenticated |<=++ || 733 || +----------------+ || || 734 || || (7) || (5) || (6) || 735 || || \/ || || 736 || || +--------+ || || 737 || || |Selected|==++ || 738 || || +--------+ || 739 || || || (7) || 740 \/ \/ \/ \/ 741 +--------------------------------------+ 742 | Logout | 743 +--------------------------------------+ 744 || 745 \/ 746 +-------------------------------+ 747 |both sides close the connection| 748 +-------------------------------+ 750 (1) connection without pre-authentication (OK greeting) 751 (2) pre-authenticated connection (PREAUTH greeting) 752 (3) rejected connection (BYE greeting) 753 (4) successful LOGIN or AUTHENTICATE command 754 (5) successful SELECT or EXAMINE command 755 (6) CLOSE command, unsolicited CLOSED response code or 756 failed SELECT or EXAMINE command 757 (7) LOGOUT command, server shutdown, or connection closed 759 4. Data Formats 761 IMAP4rev2 uses textual commands and responses. Data in IMAP4rev2 can 762 be in one of several forms: atom, number, string, parenthesized list, 763 or NIL. Note that a particular data item may take more than one 764 form; for example, a data item defined as using "astring" syntax may 765 be either an atom or a string. 767 4.1. Atom 769 An atom consists of one or more non-special characters. 771 4.1.1. Sequence set and UID set 773 A set of messages can be referenced by a sequence set containing 774 either message sequence numbers or unique identifiers. See Section 9 775 for details. Sequence sets can contain ranges (e.g. "5:50"), an 776 enumeration of specific message/UID numbers, a special symbol "*", or 777 a combination of the above. 779 A "UID set" is similar to the sequence set of unique identifiers; 780 however, the "*" value for a sequence number is not permitted. 782 4.2. Number 784 A number consists of one or more digit characters, and represents a 785 numeric value. 787 4.3. String 789 A string is in one of three forms: synchonizing literal, non- 790 synchronizing literal or quoted string. The synchronizing literal 791 form is the general form of string. The non-synchronizing literal 792 form is also the general form, but has length limitation. The quoted 793 string form is an alternative that avoids the overhead of processing 794 a literal at the cost of limitations of characters which may be used. 796 When the distinction between synchronizing and non-synchronizing 797 literals is not important, this document just uses the term 798 "literal". 800 A synchronizing literal is a sequence of zero or more octets 801 (including CR and LF), prefix-quoted with an octet count in the form 802 of an open brace ("{"), the number of octets, close brace ("}"), and 803 CRLF. In the case of synchronizing literals transmitted from server 804 to client, the CRLF is immediately followed by the octet data. In 805 the case of synchronizing literals transmitted from client to server, 806 the client MUST wait to receive a command continuation request 807 (described later in this document) before sending the octet data (and 808 the remainder of the command). 810 The non-synchronizing literal is an alternative form of synchronizing 811 literal, and it may appear in communication from client to server 812 instead of the synchonizing form of literal. The non-synchronizing 813 literal form MUST NOT be sent from server to client. The non- 814 synchronizing literal is distinguished from the synchronizing literal 815 by having a plus ("+") between the octet count and the closing brace 816 ("}"). The server does not generate a command continuation request 817 in response to a non-synchronizing literal, and clients are not 818 required to wait before sending the octets of a non- synchronizing 819 literal. Non-synchronizing literals MUST NOT be larger than 4096 820 octets. Any literal larger than 4096 bytes MUST be sent as a 821 synchronizing literal. (Non-synchronizing literals defined in this 822 document are the same as non-synchronizing literals defined by the 823 LITERAL- extension from [RFC7888]. See that document for details on 824 how to handle invalid non-synchronizing literals longer than 4096 825 octets and for interaction with other IMAP extensions.) 827 A quoted string is a sequence of zero or more Unicode characters, 828 excluding CR and LF, encoded in UTF-8, with double quote (<">) 829 characters at each end. 831 The empty string is represented as "" (a quoted string with zero 832 characters between double quotes), as {0} followed by CRLF (a 833 synchronizing literal with an octet count of 0) or as {0+} followed 834 by CRLF (a non-synchronizing literal with an octet count of 0). 836 Note: Even if the octet count is 0, a client transmitting a 837 synchronizing literal MUST wait to receive a command continuation 838 request. 840 4.3.1. 8-bit and Binary Strings 842 8-bit textual and binary mail is supported through the use of a 843 [MIME-IMB] content transfer encoding. IMAP4rev2 implementations MAY 844 transmit 8-bit or multi-octet characters in literals, but SHOULD do 845 so only when the [CHARSET] is identified. 847 IMAP4rev2 is compatible with [I18N-HDRS]. As a result, the 848 identified charset for header-field values with 8-bit content is 849 UTF-8 [UTF-8]. IMAP4rev2 implementations MUST accept and MAY 850 transmit [UTF-8] text in quoted-strings as long as the string does 851 not contain NUL, CR, or LF. This differs from IMAP4rev1 852 implementations. 854 Although a BINARY content transfer encoding is defined, unencoded 855 binary strings are not permitted, unless returned in a in 856 response to BINARY.PEEK[]<> or 857 BINARY[]<> FETCH data item. A "binary 858 string" is any string with NUL characters. A string with an 859 excessive amount of CTL characters MAY also be considered to be 860 binary. Unless returned in response to BINARY.PEEK[...]/BINARY[...] 861 FETCH, client and server implementations MUST encode binary data into 862 a textual form, such as BASE64, before transmitting the data. 864 4.4. Parenthesized List 866 Data structures are represented as a "parenthesized list"; a sequence 867 of data items, delimited by space, and bounded at each end by 868 parentheses. A parenthesized list can contain other parenthesized 869 lists, using multiple levels of parentheses to indicate nesting. 871 The empty list is represented as () -- a parenthesized list with no 872 members. 874 4.5. NIL 876 The special form "NIL" represents the non-existence of a particular 877 data item that is represented as a string or parenthesized list, as 878 distinct from the empty string "" or the empty parenthesized list (). 880 Note: NIL is never used for any data item which takes the form of 881 an atom. For example, a mailbox name of "NIL" is a mailbox named 882 NIL as opposed to a non-existent mailbox name. This is because 883 mailbox uses "astring" syntax which is an atom or a string. 884 Conversely, an addr-name of NIL is a non-existent personal name, 885 because addr-name uses "nstring" syntax which is NIL or a string, 886 but never an atom. 888 Examples: 890 The following LIST response: 892 * LIST () "/" NIL 894 is equivalent to: 896 * LIST () "/" "NIL" 898 as LIST response ABNF is using "astring" for mailbox name. 900 However, the following response 902 * FETCH 1 (BODY[1] NIL) 904 is not equivalent to: 906 * FETCH 1 (BODY[1] "NIL") 908 The former means absence of the body part, while the latter 909 means that it contains literal sequence of characters "NIL". 911 5. Operational Considerations 913 The following rules are listed here to ensure that all IMAP4rev2 914 implementations interoperate properly. 916 5.1. Mailbox Naming 918 In IMAP4rev2, Mailbox names are encoded in Net-Unicode [NET-UNICODE] 919 (this differs from IMAP4rev1). Client implementations MAY attempt to 920 create Net-Unicode mailbox names, and MUST interpret any 8-bit 921 mailbox names returned by LIST as [NET-UNICODE]. Server 922 implementations MUST prohibit the creation of 8-bit mailbox names 923 that do not comply with Net-Unicode. However, servers MAY accept a 924 de-normalized UTF-8 mailbox name and convert it to Unicode 925 normalization form "NFC" (as per Net-Unicode requirements) prior to 926 mailbox creation. Servers that choose to accept such de-normalized 927 UTF-8 mailbox names MUST accept them in all IMAP commands that have a 928 mailbox name parameter. In particular SELECT must open the 929 same mailbox that was successfully created with CREATE , even 930 if is a de-normalized UTF-8 mailbox name. 932 The case-insensitive mailbox name INBOX is a special name reserved to 933 mean "the primary mailbox for this user on this server". (Note that 934 this special name may not exist on some servers for some users, for 935 example if the user has no access to personal namespace.) The 936 interpretation of all other names is implementation-dependent. 938 In particular, this specification takes no position on case 939 sensitivity in non-INBOX mailbox names. Some server implementations 940 are fully case-sensitive in ASCII range; others preserve case of a 941 newly-created name but otherwise are case-insensitive; and yet others 942 coerce names to a particular case. Client implementations must be 943 able to interact with any of these. 945 There are certain client considerations when creating a new mailbox 946 name: 948 1. Any character which is one of the atom-specials (see the Formal 949 Syntax in Section 9) will require that the mailbox name be 950 represented as a quoted string or literal. 952 2. CTL and other non-graphic characters are difficult to represent 953 in a user interface and are best avoided. Servers MAY refuse to 954 create mailbox names containing Unicode CTL characters. 956 3. Although the list-wildcard characters ("%" and "*") are valid in 957 a mailbox name, it is difficult to use such mailbox names with 958 the LIST command due to the conflict with wildcard 959 interpretation. 961 4. Usually, a character (determined by the server implementation) is 962 reserved to delimit levels of hierarchy. 964 5. Two characters, "#" and "&", have meanings by convention, and 965 should be avoided except when used in that convention. See 966 Section 5.1.2.1 and Appendix A.1 respectively. 968 5.1.1. Mailbox Hierarchy Naming 970 If it is desired to export hierarchical mailbox names, mailbox names 971 MUST be left-to-right hierarchical using a single character to 972 separate levels of hierarchy. The same hierarchy separator character 973 is used for all levels of hierarchy within a single name. 975 5.1.2. Namespaces 977 Personal Namespace: A namespace that the server considers within the 978 personal scope of the authenticated user on a particular connection. 979 Typically, only the authenticated user has access to mailboxes in 980 their Personal Namespace. It is the part of the namespace that 981 belongs to the user that is allocated for mailboxes. If an INBOX 982 exists for a user, it MUST appear within the user's personal 983 namespace. In the typical case, there SHOULD be only one Personal 984 Namespace per user on a server. 986 Other Users' Namespace: A namespace that consists of mailboxes from 987 the Personal Namespaces of other users. To access mailboxes in the 988 Other Users' Namespace, the currently authenticated user MUST be 989 explicitly granted access rights. For example, it is common for a 990 manager to grant to their secretary access rights to their mailbox. 991 In the typical case, there SHOULD be only one Other Users' Namespace 992 per user on a server. 994 Shared Namespace: A namespace that consists of mailboxes that are 995 intended to be shared amongst users and do not exist within a user's 996 Personal Namespace. 998 The namespaces a server uses MAY differ on a per-user basis. 1000 5.1.2.1. Historic Mailbox Namespace Naming Convention 1002 By convention, the first hierarchical element of any mailbox name 1003 which begins with "#" identifies the "namespace" of the remainder of 1004 the name. This makes it possible to disambiguate between different 1005 types of mailbox stores, each of which have their own namespaces. 1007 For example, implementations which offer access to USENET 1008 newsgroups MAY use the "#news" namespace to partition the USENET 1009 newsgroup namespace from that of other mailboxes. Thus, the 1010 comp.mail.misc newsgroup would have a mailbox name of 1011 "#news.comp.mail.misc", and the name "comp.mail.misc" can refer to 1012 a different object (e.g., a user's private mailbox). 1014 Namespaces that include the "#" character are not IMAP URL [IMAP-URL] 1015 friendly requiring the "#" character to be represented as %23 when 1016 within URLs. As such, server implementors MAY instead consider using 1017 namespace prefixes that do not contain the "#" character. 1019 5.1.2.2. Common namespace models 1021 Previous version of this protocol does not define a default server 1022 namespace. Two common namespace models have evolved: 1024 The "Personal Mailbox" model, in which the default namespace that is 1025 presented consists of only the user's personal mailboxes. To access 1026 shared mailboxes, the user must use an escape mechanism to reach 1027 another namespace. 1029 The "Complete Hierarchy" model, in which the default namespace that 1030 is presented includes the user's personal mailboxes along with any 1031 other mailboxes they have access to. 1033 5.2. Mailbox Size and Message Status Updates 1035 At any time, a server can send data that the client did not request. 1036 Sometimes, such behavior is required by this specification and/or 1037 extensions. For example, agents other than the server MAY add 1038 messages to the mailbox (e.g., new message delivery), change the 1039 flags of the messages in the mailbox (e.g., simultaneous access to 1040 the same mailbox by multiple agents), or even remove messages from 1041 the mailbox. A server MUST send mailbox size updates automatically 1042 if a mailbox size change is observed during the processing of a 1043 command. A server SHOULD send message flag updates automatically, 1044 without requiring the client to request such updates explicitly. 1046 Special rules exist for server notification of a client about the 1047 removal of messages to prevent synchronization errors; see the 1048 description of the EXPUNGE response (Section 7.5.1) for more detail. 1049 In particular, it is NOT permitted to send an EXISTS response that 1050 would reduce the number of messages in the mailbox; only the EXPUNGE 1051 response can do this. 1053 Regardless of what implementation decisions a client makes on 1054 remembering data from the server, a client implementation MUST 1055 remember mailbox size updates. It MUST NOT assume that any command 1056 after the initial mailbox selection will return the size of the 1057 mailbox. 1059 5.3. Response when no Command in Progress 1061 Server implementations are permitted to send an untagged response 1062 (except for EXPUNGE) while there is no command in progress. Server 1063 implementations that send such responses MUST deal with flow control 1064 considerations. Specifically, they MUST either (1) verify that the 1065 size of the data does not exceed the underlying transport's available 1066 window size, or (2) use non-blocking writes. 1068 5.4. Autologout Timer 1070 If a server has an inactivity autologout timer that applies to 1071 sessions after authentication, the duration of that timer MUST be at 1072 least 30 minutes. The receipt of any command from the client during 1073 that interval resets the autologout timer. 1075 Note that this specification doesn't have any restrictions on 1076 autologout timer used before successful client authentication. In 1077 particular, servers are allowed to use shortened pre-authentication 1078 timer to protect themselves from Denial of Service attacks. 1080 5.5. Multiple Commands in Progress (Command Pipelining) 1082 The client MAY send another command without waiting for the 1083 completion result response of a command, subject to ambiguity rules 1084 (see below) and flow control constraints on the underlying data 1085 stream. Similarly, a server MAY begin processing another command 1086 before processing the current command to completion, subject to 1087 ambiguity rules. However, any command continuation request responses 1088 and command continuations MUST be negotiated before any subsequent 1089 command is initiated. 1091 The exception is if an ambiguity would result because of a command 1092 that would affect the results of other commands. If the server 1093 detects a possible ambiguity, it MUST execute commands to completion 1094 in the order given by the client. 1096 The most obvious example of ambiguity is when a command would affect 1097 the results of another command, e.g., a FETCH of a message's flags 1098 and a STORE of that same message's flags. 1100 A non-obvious ambiguity occurs with commands that permit an untagged 1101 EXPUNGE response (commands other than FETCH, STORE, and SEARCH), 1102 since an untagged EXPUNGE response can invalidate sequence numbers in 1103 a subsequent command. This is not a problem for FETCH, STORE, or 1104 SEARCH commands because servers are prohibited from sending EXPUNGE 1105 responses while any of those commands are in progress. Therefore, if 1106 the client sends any command other than FETCH, STORE, or SEARCH, it 1107 MUST wait for the completion result response before sending a command 1108 with message sequence numbers. 1110 Note: EXPUNGE responses are permitted while UID FETCH, UID STORE, 1111 and UID SEARCH are in progress. If the client sends a UID 1112 command, it MUST wait for a completion result response before 1113 sending a command which uses message sequence numbers (this may 1114 include UID SEARCH). Any message sequence numbers in an argument 1115 to UID SEARCH are associated with messages prior to the effect of 1116 any untagged EXPUNGE returned by the UID SEARCH. 1118 For example, the following non-waiting command sequences are invalid: 1120 FETCH + NOOP + STORE 1122 STORE + COPY + FETCH 1124 COPY + COPY 1126 The following are examples of valid non-waiting command sequences: 1128 FETCH + STORE + SEARCH + NOOP 1130 STORE + COPY + EXPUNGE 1132 UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting 1133 command sequence, depending upon whether or not the second UID 1134 SEARCH contains message sequence numbers. 1136 Use of SEARCH result variable (see Section 6.4.4.1) creates direct 1137 dependency between two commands. See Section 6.4.4.2 for more 1138 considerations about pipelining such dependent commands. 1140 6. Client Commands 1142 IMAP4rev2 commands are described in this section. Commands are 1143 organized by the state in which the command is permitted. Commands 1144 which are permitted in multiple states are listed in the minimum 1145 permitted state (for example, commands valid in authenticated and 1146 selected state are listed in the authenticated state commands). 1148 Command arguments, identified by "Arguments:" in the command 1149 descriptions below, are described by function, not by syntax. The 1150 precise syntax of command arguments is described in the Formal Syntax 1151 (Section 9). 1153 Some commands cause specific server responses to be returned; these 1154 are identified by "Responses:" in the command descriptions below. 1155 See the response descriptions in the Responses section (Section 7) 1156 for information on these responses, and the Formal Syntax (Section 9) 1157 for the precise syntax of these responses. It is possible for server 1158 data to be transmitted as a result of any command. Thus, commands 1159 that do not specifically require server data specify "no specific 1160 responses for this command" instead of "none". 1162 The "Result:" in the command description refers to the possible 1163 tagged status responses to a command, and any special interpretation 1164 of these status responses. 1166 The state of a connection is only changed by successful commands 1167 which are documented as changing state. A rejected command (BAD 1168 response) never changes the state of the connection or of the 1169 selected mailbox. A failed command (NO response) generally does not 1170 change the state of the connection or of the selected mailbox; the 1171 exception being the SELECT and EXAMINE commands. 1173 6.1. Client Commands - Any State 1175 The following commands are valid in any state: CAPABILITY, NOOP, and 1176 LOGOUT. 1178 6.1.1. CAPABILITY Command 1180 Arguments: none 1182 Responses: REQUIRED untagged response: CAPABILITY 1184 Result: OK - capability completed 1185 BAD - arguments invalid 1187 The CAPABILITY command requests a listing of capabilities (e.g. 1188 extensions and/or modifications of server behaviour) that the server 1189 supports. The server MUST send a single untagged CAPABILITY response 1190 with "IMAP4rev2" as one of the listed capabilities before the 1191 (tagged) OK response. 1193 A capability name which begins with "AUTH=" indicates that the server 1194 supports that particular authentication mechanism as defined in 1195 [SASL]. All such names are, by definition, part of this 1196 specification. 1198 Other capability names refer to extensions, revisions, or amendments 1199 to this specification. See the documentation of the CAPABILITY 1200 response in Section 7.2.2 for additional information. No 1201 capabilities, beyond the base IMAP4rev2 set defined in this 1202 specification, are enabled without explicit client action to invoke 1203 the capability. 1205 Client and server implementations MUST implement the STARTTLS 1206 Section 6.2.1, LOGINDISABLED, and AUTH=PLAIN (described in [PLAIN]) 1207 capabilities. See the Security Considerations (Section 11) for 1208 important information. 1210 Unless specified otherwise, all registered extensions to IMAP4rev1 1211 are also valid extensions to IMAP4rev2. 1213 Example: C: abcd CAPABILITY 1214 S: * CAPABILITY IMAP4rev2 STARTTLS AUTH=GSSAPI 1215 LOGINDISABLED 1216 S: abcd OK CAPABILITY completed 1217 C: efgh STARTTLS 1218 S: efgh OK STARTLS completed 1219 1220 C: ijkl CAPABILITY 1221 S: * CAPABILITY IMAP4rev2 AUTH=GSSAPI AUTH=PLAIN 1222 S: ijkl OK CAPABILITY completed 1224 6.1.2. NOOP Command 1226 Arguments: none 1228 Responses: no specific responses for this command (but see below) 1230 Result: OK - noop completed 1231 BAD - command unknown or arguments invalid 1233 The NOOP command always succeeds. It does nothing. 1235 Since any command can return a status update as untagged data, the 1236 NOOP command can be used as a periodic poll for new messages or 1237 message status updates during a period of inactivity (the IDLE 1238 command Section 6.3.13 should be used instead of NOOP if real-time 1239 updates to mailbox state are desirable). The NOOP command can also 1240 be used to reset any inactivity autologout timer on the server. 1242 Example: C: a002 NOOP 1243 S: a002 OK NOOP completed 1244 . . . 1245 C: a047 NOOP 1246 S: * 22 EXPUNGE 1247 S: * 23 EXISTS 1248 S: * 14 FETCH (UID 1305 FLAGS (\Seen \Deleted)) 1249 S: a047 OK NOOP completed 1251 6.1.3. LOGOUT Command 1253 Arguments: none 1255 Responses: REQUIRED untagged response: BYE 1257 Result: OK - logout completed 1258 BAD - command unknown or arguments invalid 1260 The LOGOUT command informs the server that the client is done with 1261 the connection. The server MUST send a BYE untagged response before 1262 the (tagged) OK response, and then close the network connection. 1264 Example: C: A023 LOGOUT 1265 S: * BYE IMAP4rev2 Server logging out 1266 S: A023 OK LOGOUT completed 1267 (Server and client then close the connection) 1269 6.2. Client Commands - Not Authenticated State 1271 In the not authenticated state, the AUTHENTICATE or LOGIN command 1272 establishes authentication and enters the authenticated state. The 1273 AUTHENTICATE command provides a general mechanism for a variety of 1274 authentication techniques, privacy protection, and integrity 1275 checking; whereas the LOGIN command uses a traditional user name and 1276 plaintext password pair and has no means of establishing privacy 1277 protection or integrity checking. 1279 The STARTTLS command is an alternative form of establishing session 1280 privacy protection and integrity checking, but does not by itself 1281 establish authentication or enter the authenticated state. 1283 Server implementations MAY allow access to certain mailboxes without 1284 establishing authentication. This can be done by means of the 1285 ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older 1286 convention is a LOGIN command using the userid "anonymous"; in this 1287 case, a password is required although the server may choose to accept 1288 any password. The restrictions placed on anonymous users are 1289 implementation-dependent. 1291 Once authenticated (including as anonymous), it is not possible to 1292 re-enter not authenticated state. 1294 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 1295 the following commands are valid in the not authenticated state: 1296 STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations 1297 (Section 11) for important information about these commands. 1299 6.2.1. STARTTLS Command 1301 Arguments: none 1303 Responses: no specific response for this command 1305 Result: OK - starttls completed, begin TLS negotiation 1306 NO - TLS negotiation can't be initiated, due to server 1307 configuration error 1308 BAD - STARTTLS received after a successful TLS 1309 negotiation or arguments invalid 1311 A TLS [TLS-1.3] negotiation begins immediately after the CRLF at the 1312 end of the tagged OK response from the server. Once a client issues 1313 a STARTTLS command, it MUST NOT issue further commands until a server 1314 response is seen and the TLS negotiation is complete. Some past 1315 server implementation incorrectly implemented STARTTLS processing and 1316 are known to contain STARTTLS plaintext command injection 1317 vulnerability [CERT-555316]. In order to avoid this vulnerability, 1318 server implementations MUST do one of the following If any data is 1319 received in the same TCP buffer after the CRLF that starts the 1320 STARTTLS command: 1322 1. Extra data from the TCP buffer is interpreted as beginning of the 1323 TLS handshake. (If the data is in cleartext, this will result in 1324 the TLS handshake failing.) 1326 2. Extra data from the TCP buffer is thrown away. 1328 Note that the first option is friendlier to clients that pipeline 1329 beginning of STARTTLS command with TLS handshake data. 1331 After successful TLS negotiation the server remains in the non- 1332 authenticated state, even if client credentials are supplied during 1333 the TLS negotiation. This does not preclude an authentication 1334 mechanism such as EXTERNAL (defined in [SASL]) from using client 1335 identity determined by the TLS negotiation. 1337 Once TLS has been started, the client MUST discard cached information 1338 about server capabilities and SHOULD re-issue the CAPABILITY command. 1339 This is necessary to protect against man-in- the-middle attacks which 1340 alter the capabilities list prior to STARTTLS. The server MAY 1341 advertise different capabilities, and in particular SHOULD NOT 1342 advertise the STARTTLS capability, after a successful STARTTLS 1343 command. 1345 Example: C: a001 CAPABILITY 1346 S: * CAPABILITY IMAP4rev2 STARTTLS LOGINDISABLED 1347 S: a001 OK CAPABILITY completed 1348 C: a002 STARTTLS 1349 S: a002 OK Begin TLS negotiation now 1350 1351 C: a003 CAPABILITY 1352 S: * CAPABILITY IMAP4rev2 AUTH=PLAIN 1353 S: a003 OK CAPABILITY completed 1354 C: a004 LOGIN joe password 1355 S: a004 OK LOGIN completed 1357 6.2.2. AUTHENTICATE Command 1359 Arguments: SASL authentication mechanism name 1360 OPTIONAL initial response 1362 Responses: continuation data can be requested 1364 Result: OK - authenticate completed, now in authenticated state 1365 NO - authenticate failure: unsupported authentication 1366 mechanism, credentials rejected 1367 BAD - command unknown or arguments invalid, 1368 authentication exchange cancelled 1370 The AUTHENTICATE command indicates a [SASL] authentication mechanism 1371 to the server. If the server supports the requested authentication 1372 mechanism, it performs an authentication protocol exchange to 1373 authenticate and identify the client. It MAY also negotiate an 1374 OPTIONAL security layer for subsequent protocol interactions. If the 1375 requested authentication mechanism is not supported, the server 1376 SHOULD reject the AUTHENTICATE command by sending a tagged NO 1377 response. 1379 The AUTHENTICATE command supports the optional "initial response" 1380 feature defined in Section 5.1 of [SASL]. The client doesn't need to 1381 use it. If a SASL mechanism supports "initial response", but it is 1382 not specified by the client, the server handles this as specified in 1383 Section 3 of [SASL]. 1385 The service name specified by this protocol's profile of [SASL] is 1386 "imap". 1388 The authentication protocol exchange consists of a series of server 1389 challenges and client responses that are specific to the 1390 authentication mechanism. A server challenge consists of a command 1391 continuation request response with the "+" token followed by a BASE64 1392 encoded (see Section 4 of [RFC4648]) string. The client response 1393 consists of a single line consisting of a BASE64 encoded string. If 1394 the client wishes to cancel an authentication exchange, it issues a 1395 line consisting of a single "*". If the server receives such a 1396 response, or if it receives an invalid BASE64 string (e.g. 1397 characters outside the BASE64 alphabet, or non-terminal "="), it MUST 1398 reject the AUTHENTICATE command by sending a tagged BAD response. 1400 As with any other client response, this initial response MUST be 1401 encoded as BASE64. It also MUST be transmitted outside of a quoted 1402 string or literal. To send a zero-length initial response, the 1403 client MUST send a single pad character ("="). This indicates that 1404 the response is present, but is a zero-length string. 1406 When decoding the BASE64 data in the initial response, decoding 1407 errors MUST be treated as in any normal SASL client response, i.e. 1408 with a tagged BAD response. In particular, the server should check 1409 for any characters not explicitly allowed by the BASE64 alphabet, as 1410 well as any sequence of BASE64 characters that contains the pad 1411 character ('=') anywhere other than the end of the string (e.g., 1412 "=AAA" and "AAA=BBB" are not allowed). 1414 If the client uses an initial response with a SASL mechanism that 1415 does not support an initial response, the server MUST reject the 1416 command with a tagged BAD response. 1418 If a security layer is negotiated through the [SASL] authentication 1419 exchange, it takes effect immediately following the CRLF that 1420 concludes the authentication exchange for the client, and the CRLF of 1421 the tagged OK response for the server. 1423 While client and server implementations MUST implement the 1424 AUTHENTICATE command itself, it is not required to implement any 1425 authentication mechanisms other than the PLAIN mechanism described in 1426 [PLAIN]. Also, an authentication mechanism is not required to 1427 support any security layers. 1429 Note: a server implementation MUST implement a configuration in 1430 which it does NOT permit any plaintext password mechanisms, unless 1431 either the STARTTLS command has been negotiated, TLS has been 1432 negotiated on an Implicit TLS port, or some other mechanism that 1433 protects the session from password snooping has been provided. 1434 Server sites SHOULD NOT use any configuration which permits a 1435 plaintext password mechanism without such a protection mechanism 1436 against password snooping. Client and server implementations 1437 SHOULD implement additional [SASL] mechanisms that do not use 1438 plaintext passwords, such the GSSAPI mechanism described in 1439 [RFC4752], the SCRAM-SHA-256/SCRAM-SHA-256-PLUS [SCRAM-SHA-256] 1440 mechanisms and/or EXTERNAL [SASL] mechanism for mutual TLS 1441 authentication. (Note that SASL framework allows creation of SASL 1442 mechanisms that support 2FA (2-factor authentication), however 1443 none are fully ready to be recommended by this document.) 1445 Servers and clients can support multiple authentication mechanisms. 1446 The server SHOULD list its supported authentication mechanisms in the 1447 response to the CAPABILITY command so that the client knows which 1448 authentication mechanisms to use. 1450 A server MAY include a CAPABILITY response code in the tagged OK 1451 response of a successful AUTHENTICATE command in order to send 1452 capabilities automatically. It is unnecessary for a client to send a 1453 separate CAPABILITY command if it recognizes these automatic 1454 capabilities. This should only be done if a security layer was not 1455 negotiated by the AUTHENTICATE command, because the tagged OK 1456 response as part of an AUTHENTICATE command is not protected by 1457 encryption/integrity checking. [SASL] requires the client to re- 1458 issue a CAPABILITY command in this case. The server MAY advertise 1459 different capabilities after a successful AUTHENTICATE command. 1461 If an AUTHENTICATE command fails with a NO response, the client MAY 1462 try another authentication mechanism by issuing another AUTHENTICATE 1463 command. It MAY also attempt to authenticate by using the LOGIN 1464 command (see Section 6.2.3 for more detail). In other words, the 1465 client MAY request authentication types in decreasing order of 1466 preference, with the LOGIN command as a last resort. 1468 The authorization identity passed from the client to the server 1469 during the authentication exchange is interpreted by the server as 1470 the user name whose privileges the client is requesting. 1472 Example: S: * OK IMAP4rev2 Server 1473 C: A001 AUTHENTICATE GSSAPI 1474 S: + 1475 C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw 1476 MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0 1477 b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW 1478 Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA 1479 cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX 1480 AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y 1481 C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb 1482 I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi 1483 vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL 1484 pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n 1485 FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE 1486 NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx 1487 O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB 1488 vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg== 1489 S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC 1490 AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0 1491 uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg== 1492 C: 1493 S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe 1494 ceP2CWY0SR0fAQAgAAQEBAQ= 1495 C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP 1496 wkhbfa2QteAQAgAG1yYwE= 1497 S: A001 OK GSSAPI authentication successful 1499 Note: The line breaks within server challenges and client responses 1500 are for editorial clarity and are not in real authenticators. 1502 6.2.3. LOGIN Command 1504 Arguments: user name 1505 password 1507 Responses: no specific responses for this command 1509 Result: OK - login completed, now in authenticated state 1510 NO - login failure: user name or password rejected 1511 BAD - command unknown or arguments invalid 1513 The LOGIN command identifies the client to the server and carries the 1514 plaintext password authenticating this user. The LOGIN command 1515 SHOULD NOT be used except as a last resort (after attempting and 1516 failing to authenticate using the AUTHENTICATE command one or more 1517 times), and it is recommended that client implementations have a 1518 means to disable any automatic use of the LOGIN command. 1520 A server MAY include a CAPABILITY response code in the tagged OK 1521 response to a successful LOGIN command in order to send capabilities 1522 automatically. It is unnecessary for a client to send a separate 1523 CAPABILITY command if it recognizes these automatic capabilities. 1525 Example: C: a001 LOGIN SMITH SESAME 1526 S: a001 OK LOGIN completed 1528 Note: Use of the LOGIN command over an insecure network (such as the 1529 Internet) is a security risk, because anyone monitoring network 1530 traffic can obtain plaintext passwords. For that reason clients MUST 1531 NOT use LOGIN on unsecure networks. 1533 Unless either the client is accessing IMAP service on Implicit TLS 1534 port [RFC8314], the STARTTLS command has been negotiated or some 1535 other mechanism that protects the session from password snooping has 1536 been provided, a server implementation MUST implement a configuration 1537 in which it advertises the LOGINDISABLED capability and does NOT 1538 permit the LOGIN command. Server sites SHOULD NOT use any 1539 configuration which permits the LOGIN command without such a 1540 protection mechanism against password snooping. A client 1541 implementation MUST NOT send a LOGIN command if the LOGINDISABLED 1542 capability is advertised. 1544 6.3. Client Commands - Authenticated State 1546 In the authenticated state, commands that manipulate mailboxes as 1547 atomic entities are permitted. Of these commands, the SELECT and 1548 EXAMINE commands will select a mailbox for access and enter the 1549 selected state. 1551 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 1552 the following commands are valid in the authenticated state: ENABLE, 1553 SELECT, EXAMINE, NAMESPACE, CREATE, DELETE, RENAME, SUBSCRIBE, 1554 UNSUBSCRIBE, LIST, STATUS, APPEND and IDLE. 1556 6.3.1. ENABLE Command 1558 Arguments: capability names 1560 Responses: no specific responses for this command 1562 Result: OK - Relevant capabilities enabled 1563 BAD - No arguments, or syntax error in an argument 1565 Several IMAP extensions allow the server to return unsolicited 1566 responses specific to these extensions in certain circumstances. 1567 However, servers cannot send those unsolicited responses (with the 1568 exception of response codes (see Section 7.1) included in tagged or 1569 untagged OK/NO/BAD responses, which can always be sent) until they 1570 know that the clients support such extensions and thus won't choke on 1571 the extension response data. 1573 The ENABLE command provides an explicit indication from the client 1574 that it supports particular extensions. It is designed such that the 1575 client can send a simple constant string with the extensions it 1576 supports, and the server will enable the shared subset that both 1577 support. 1579 The ENABLE command takes a list of capability names, and requests the 1580 server to enable the named extensions. Once enabled using ENABLE, 1581 each extension remains active until the IMAP connection is closed. 1582 For each argument, the server does the following: 1584 o If the argument is not an extension known to the server, the 1585 server MUST ignore the argument. 1587 o If the argument is an extension known to the server, and it is not 1588 specifically permitted to be enabled using ENABLE, the server MUST 1589 ignore the argument. (Note that knowing about an extension 1590 doesn't necessarily imply supporting that extension.) 1592 o If the argument is an extension that is supported by the server 1593 and that needs to be enabled, the server MUST enable the extension 1594 for the duration of the connection. Note that once an extension 1595 is enabled, there is no way to disable it. 1597 If the ENABLE command is successful, the server MUST send an untagged 1598 ENABLED response Section 7.2.1, which includes all enabled extensions 1599 as specified above. The ENABLED response is sent even if no 1600 extensions were enabled. 1602 Clients SHOULD only include extensions that need to be enabled by the 1603 server. For example, a client can enable IMAP4rev2 specific 1604 behaviour when both IMAP4rev1 and IMAP4rev2 are advertised in the 1605 CAPABILITY response. Future RFCs may add to this list. 1607 The ENABLE command is only valid in the authenticated state, before 1608 any mailbox is selected. Clients MUST NOT issue ENABLE once they 1609 SELECT/EXAMINE a mailbox; however, server implementations don't have 1610 to check that no mailbox is selected or was previously selected 1611 during the duration of a connection. 1613 The ENABLE command can be issued multiple times in a session. It is 1614 additive; i.e., "ENABLE a b", followed by "ENABLE c" is the same as a 1615 single command "ENABLE a b c". When multiple ENABLE commands are 1616 issued, each corresponding ENABLED response SHOULD only contain 1617 extensions enabled by the corresponding ENABLE command, i.e. for the 1618 above example, the ENABLED response to "ENABLE c" should not contain 1619 "a" or "b". 1621 There are no limitations on pipelining ENABLE. For example, it is 1622 possible to send ENABLE and then immediately SELECT, or a LOGIN 1623 immediately followed by ENABLE. 1625 The server MUST NOT change the CAPABILITY list as a result of 1626 executing ENABLE; i.e., a CAPABILITY command issued right after an 1627 ENABLE command MUST list the same capabilities as a CAPABILITY 1628 command issued before the ENABLE command. This is demonstrated in 1629 the following example. Note that below "X-GOOD-IDEA" is a fictitious 1630 extension capability that can be ENABLEd. 1632 C: t1 CAPABILITY 1633 S: * CAPABILITY IMAP4rev2 ID LITERAL+ X-GOOD-IDEA 1634 S: t1 OK foo 1635 C: t2 ENABLE CONDSTORE X-GOOD-IDEA 1636 S: * ENABLED X-GOOD-IDEA 1637 S: t2 OK foo 1638 C: t3 CAPABILITY 1639 S: * CAPABILITY IMAP4rev2 ID LITERAL+ X-GOOD-IDEA 1640 S: t3 OK foo again 1642 In the following example, the client enables CONDSTORE: 1644 C: a1 ENABLE CONDSTORE 1645 S: * ENABLED CONDSTORE 1646 S: a1 OK Conditional Store enabled 1648 6.3.1.1. Note to Designers of Extensions That May Use the ENABLE 1649 Command 1651 Designers of IMAP extensions are discouraged from creating extensions 1652 that require ENABLE unless there is no good alternative design. 1653 Specifically, extensions that cause potentially incompatible behavior 1654 changes to deployed server responses (and thus benefit from ENABLE) 1655 have a higher complexity cost than extensions that do not. 1657 6.3.2. SELECT Command 1659 Arguments: mailbox name 1661 Responses: REQUIRED untagged responses: FLAGS, EXISTS 1662 REQUIRED OK untagged responses: PERMANENTFLAGS, 1663 UIDNEXT, UIDVALIDITY 1664 REQUIRED untagged response: LIST 1666 Result: OK - select completed, now in selected state 1667 NO - select failure, now in authenticated state: no 1668 such mailbox, can't access mailbox 1669 BAD - command unknown or arguments invalid 1671 The SELECT command selects a mailbox so that messages in the mailbox 1672 can be accessed. Before returning an OK to the client, the server 1673 MUST send the following untagged data to the client. (The order of 1674 individual responses is not important.) Note that earlier versions 1675 of this protocol (e.g. IMAP2bis) only required the FLAGS and EXISTS 1676 untagged data; consequently, client implementations SHOULD implement 1677 default behavior for missing data as discussed with the individual 1678 item. 1680 FLAGS Defined flags in the mailbox. See the description of the 1681 FLAGS response in Section 7.3.5 for more detail. 1683 EXISTS The number of messages in the mailbox. See the 1684 description of the EXISTS response in Section 7.4.1 for more 1685 detail. 1687 LIST The server MUST return a LIST response with the mailbox name. 1688 If the server allows de-normalized UTF-8 mailbox names (see 1689 Section 5.1) and the supplied mailbox name differs from the 1690 normalized version, the server MUST return LIST with the OLDNAME 1691 extended data item. See Section 6.3.9.7 for more details. 1693 OK [PERMANENTFLAGS ()] A list of message flags that 1694 the client can change permanently. If this is missing, the client 1695 should assume that all flags can be changed permanently. 1697 OK [UIDNEXT ] The next unique identifier value. Refer to 1698 Section 2.3.1.1 for more information. 1700 OK [UIDVALIDITY ] The unique identifier validity value. Refer to 1701 Section 2.3.1.1 for more information. 1703 Only one mailbox can be selected at a time in a connection; 1704 simultaneous access to multiple mailboxes requires multiple 1705 connections. The SELECT command automatically deselects any 1706 currently selected mailbox before attempting the new selection. 1707 Consequently, if a mailbox is selected and a SELECT command that 1708 fails is attempted, no mailbox is selected. When deselecting a 1709 selected mailbox, the server MUST return an untagged OK response with 1710 the "[CLOSED]" response code when the currently selected mailbox is 1711 closed (see Paragraph 10). 1713 If the client is permitted to modify the mailbox, the server SHOULD 1714 prefix the text of the tagged OK response with the "[READ-WRITE]" 1715 response code. 1717 If the client is not permitted to modify the mailbox but is permitted 1718 read access, the mailbox is selected as read-only, and the server 1719 MUST prefix the text of the tagged OK response to SELECT with the 1720 "[READ-ONLY]" response code. Read-only access through SELECT differs 1721 from the EXAMINE command in that certain read-only mailboxes MAY 1722 permit the change of permanent state on a per-user (as opposed to 1723 global) basis. Netnews messages marked in a server-based .newsrc 1724 file are an example of such per-user permanent state that can be 1725 modified with read-only mailboxes. 1727 Example: C: A142 SELECT INBOX 1728 S: * 172 EXISTS 1729 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1730 S: * OK [UIDNEXT 4392] Predicted next UID 1731 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1732 S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited 1733 S: * LIST () "/" INBOX 1734 S: A142 OK [READ-WRITE] SELECT completed 1736 Example: C: A142 SELECT INBOX 1737 S: * 172 EXISTS 1738 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1739 S: * OK [UIDNEXT 4392] Predicted next UID 1740 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1741 S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited 1742 S: A142 OK [READ-WRITE] SELECT completed 1743 [...some time later...] 1744 C: A143 SELECT Drafts 1745 S: * OK [CLOSED] Previous mailbox is now closed 1746 S: * 5 EXISTS 1747 S: * OK [UIDVALIDITY 9877410381] UIDs valid 1748 S: * OK [UIDNEXT 102] Predicted next UID 1749 S: * LIST () "/" Drafts 1750 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1751 S: * OK [PERMANENTFLAGS (\Deleted \Seen \Answered 1752 \Flagged \Draft \*)] System flags and keywords allowed 1753 S: A143 OK [READ-WRITE] SELECT completed 1755 Note that IMAP4rev1 compliant servers can also send the untagged 1756 RECENT response which was deprecated in IMAP4rev2. E.g. "* 0 1757 RECENT". Pure IMAP4rev2 clients are advised to ignore the untagged 1758 RECENT response. 1760 6.3.3. EXAMINE Command 1762 Arguments: mailbox name 1764 Responses: REQUIRED untagged responses: FLAGS, EXISTS 1765 REQUIRED OK untagged responses: PERMANENTFLAGS, 1766 UIDNEXT, UIDVALIDITY 1767 REQUIRED untagged response: LIST 1769 Result: OK - examine completed, now in selected state 1770 NO - examine failure, now in authenticated state: no 1771 such mailbox, can't access mailbox BAD - command unknown 1772 or arguments invalid 1774 The EXAMINE command is identical to SELECT and returns the same 1775 output; however, the selected mailbox is identified as read-only. No 1776 changes to the permanent state of the mailbox, including per-user 1777 state, are permitted. 1779 The text of the tagged OK response to the EXAMINE command MUST begin 1780 with the "[READ-ONLY]" response code. 1782 Example: C: A932 EXAMINE blurdybloop 1783 S: * 17 EXISTS 1784 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1785 S: * OK [UIDNEXT 4392] Predicted next UID 1786 S: * LIST () "/" blurdybloop 1787 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1788 S: * OK [PERMANENTFLAGS ()] No permanent flags permitted 1789 S: A932 OK [READ-ONLY] EXAMINE completed 1791 6.3.4. CREATE Command 1793 Arguments: mailbox name 1795 Responses: OPTIONAL untagged response: LIST 1797 Result: OK - create completed 1798 NO - create failure: can't create mailbox with that name 1799 BAD - command unknown or arguments invalid 1801 The CREATE command creates a mailbox with the given name. An OK 1802 response is returned only if a new mailbox with that name has been 1803 created. It is an error to attempt to create INBOX or a mailbox with 1804 a name that refers to an extant mailbox. Any error in creation will 1805 return a tagged NO response. If a client attempts to create a UTF-8 1806 mailbox name that is not a valid Net-Unicode name, the server MUST 1807 reject the creation or convert the name to Net-Unicode prior to 1808 creating the mailbox. If the server decides to convert (normalize) 1809 the name, it SHOULD return an untagged LIST with OLDNAME extended 1810 data item, with the OLDNAME value being the supplied mailbox name and 1811 the name parameter being the normalized mailbox name. (See 1812 Section 6.3.9.7 for more details.) 1814 Mailboxes created in one IMAP session MAY be announced to other IMAP 1815 sessions using unsolicited LIST response. If the server 1816 automatically subscribes a mailbox when it is created, then the 1817 unsolicited LIST response for each affected subscribed mailbox name 1818 MUST include the \Subscribed attribute. 1820 If the mailbox name is suffixed with the server's hierarchy separator 1821 character (as returned from the server by a LIST command), this is a 1822 declaration that the client intends to create mailbox names under 1823 this name in the hierarchy. Server implementations that do not 1824 require this declaration MUST ignore the declaration. In any case, 1825 the name created is without the trailing hierarchy delimiter. 1827 If the server's hierarchy separator character appears elsewhere in 1828 the name, the server SHOULD create any superior hierarchical names 1829 that are needed for the CREATE command to be successfully completed. 1831 In other words, an attempt to create "foo/bar/zap" on a server in 1832 which "/" is the hierarchy separator character SHOULD create foo/ and 1833 foo/bar/ if they do not already exist. 1835 If a new mailbox is created with the same name as a mailbox which was 1836 deleted, its unique identifiers MUST be greater than any unique 1837 identifiers used in the previous incarnation of the mailbox unless 1838 the new incarnation has a different unique identifier validity value. 1839 See the description of the UID command in Section 6.4.9 for more 1840 detail. 1842 Example: C: A003 CREATE owatagusiam/ 1843 S: A003 OK CREATE completed 1844 C: A004 CREATE owatagusiam/blurdybloop 1845 S: A004 OK CREATE completed 1846 C: A005 CREATE NonNormalized 1847 S: * LIST () "/" "Normalized" ("OLDNAME" ("NonNormalized")) 1848 S: A005 OK CREATE completed 1850 (in the last example imagine that "NonNormalized" is 1851 a non NFC normalized Unicode mailbox name and that 1852 "Normalized" is its NFC normalized version.) 1854 Note: The interpretation of this example depends on whether "/" 1855 was returned as the hierarchy separator from LIST. If "/" is the 1856 hierarchy separator, a new level of hierarchy named "owatagusiam" 1857 with a member called "blurdybloop" is created. Otherwise, two 1858 mailboxes at the same hierarchy level are created. 1860 6.3.5. DELETE Command 1862 Arguments: mailbox name 1864 Responses: OPTIONAL untagged response: LIST 1866 Result: OK - delete completed 1867 NO - delete failure: can't delete mailbox with that name 1868 BAD - command unknown or arguments invalid 1870 The DELETE command permanently removes the mailbox with the given 1871 name. A tagged OK response is returned only if the mailbox has been 1872 deleted. It is an error to attempt to delete INBOX or a mailbox name 1873 that does not exist. 1875 The DELETE command MUST NOT remove inferior hierarchical names. For 1876 example, if a mailbox "foo" has an inferior "foo.bar" (assuming "." 1877 is the hierarchy delimiter character), removing "foo" MUST NOT remove 1878 "foo.bar". It is an error to attempt to delete a name that has 1879 inferior hierarchical names and also has the \Noselect mailbox name 1880 attribute (see the description of the LIST response (Section 7.3.1) 1881 for more details). 1883 It is permitted to delete a name that has inferior hierarchical names 1884 and does not have the \Noselect mailbox name attribute. If the 1885 server implementation does not permit deleting the name while 1886 inferior hierarchical names exists then it SHOULD disallow the DELETE 1887 command by returning a tagged NO response. The NO response SHOULD 1888 include the HASCHILDREN response code. Alternatively the server MAY 1889 allow the DELETE command, but sets the \Noselect mailbox name 1890 attribute for that name. 1892 If the server returns OK response, all messages in that mailbox are 1893 removed by the DELETE command. 1895 The value of the highest-used unique identifier of the deleted 1896 mailbox MUST be preserved so that a new mailbox created with the same 1897 name will not reuse the identifiers of the former incarnation, unless 1898 the new incarnation has a different unique identifier validity value. 1899 See the description of the UID command in Section 6.4.9 for more 1900 detail. 1902 If the server decides to convert (normalize) the mailbox name, it 1903 SHOULD return an untagged LIST with the "\NonExistent" attribute and 1904 OLDNAME extended data item, with the OLDNAME value being the supplied 1905 mailbox name and the name parameter being the normalized mailbox 1906 name. (See Section 6.3.9.7 for more details.) 1908 Mailboxes deleted in one IMAP session MAY be announced to other IMAP 1909 sessions using unsolicited LIST response, containing the 1910 "\NonExistent" attribute. 1912 Examples: C: A682 LIST "" * 1913 S: * LIST () "/" blurdybloop 1914 S: * LIST (\Noselect) "/" foo 1915 S: * LIST () "/" foo/bar 1916 S: A682 OK LIST completed 1917 C: A683 DELETE blurdybloop 1918 S: A683 OK DELETE completed 1919 C: A684 DELETE foo 1920 S: A684 NO Name "foo" has inferior hierarchical names 1921 C: A685 DELETE foo/bar 1922 S: A685 OK DELETE Completed 1923 C: A686 LIST "" * 1924 S: * LIST (\Noselect) "/" foo 1925 S: A686 OK LIST completed 1926 C: A687 DELETE foo 1927 S: A687 OK DELETE Completed 1928 C: A82 LIST "" * 1929 S: * LIST () "." blurdybloop 1930 S: * LIST () "." foo 1931 S: * LIST () "." foo.bar 1932 S: A82 OK LIST completed 1933 C: A83 DELETE blurdybloop 1934 S: A83 OK DELETE completed 1935 C: A84 DELETE foo 1936 S: A84 OK DELETE Completed 1937 C: A85 LIST "" * 1938 S: * LIST () "." foo.bar 1939 S: A85 OK LIST completed 1940 C: A86 LIST "" % 1941 S: * LIST (\Noselect) "." foo 1942 S: A86 OK LIST completed 1944 6.3.6. RENAME Command 1946 Arguments: existing mailbox name 1947 new mailbox name 1949 Responses: OPTIONAL untagged response: LIST 1951 Result: OK - rename completed 1952 NO - rename failure: can't rename mailbox with that name, 1953 can't rename to mailbox with that name 1954 BAD - command unknown or arguments invalid 1956 The RENAME command changes the name of a mailbox. A tagged OK 1957 response is returned only if the mailbox has been renamed. It is an 1958 error to attempt to rename from a mailbox name that does not exist or 1959 to a mailbox name that already exists. Any error in renaming will 1960 return a tagged NO response. 1962 If the name has inferior hierarchical names, then the inferior 1963 hierarchical names MUST also be renamed. For example, a rename of 1964 "foo" to "zap" will rename "foo/bar" (assuming "/" is the hierarchy 1965 delimiter character) to "zap/bar". 1967 If the server's hierarchy separator character appears in the name, 1968 the server SHOULD create any superior hierarchical names that are 1969 needed for the RENAME command to complete successfully. In other 1970 words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a 1971 server in which "/" is the hierarchy separator character in the 1972 corresponding namespace SHOULD create baz/ and baz/rag/ if they do 1973 not already exist. 1975 The value of the highest-used unique identifier of the old mailbox 1976 name MUST be preserved so that a new mailbox created with the same 1977 name will not reuse the identifiers of the former incarnation, unless 1978 the new incarnation has a different unique identifier validity value. 1979 See the description of the UID command in Section 6.4.9 for more 1980 detail. 1982 Renaming INBOX is permitted (i.e. it doesn't result in a tagged BAD 1983 response), and has special behavior. (Note that some servers 1984 disallow renaming INBOX by returning a tagged NO response, so clients 1985 need to be able to handle such RENAME failing). It moves all 1986 messages in INBOX to a new mailbox with the given name, leaving INBOX 1987 empty. If the server implementation supports inferior hierarchical 1988 names of INBOX, these are unaffected by a rename of INBOX. 1990 If the server allows creation of mailboxes with names that are not 1991 valid Net-Unicode names, the server normalizes both the existing 1992 mailbox name parameter and the new mailbox name parameter. If the 1993 normalized version of any of these 2 parameters differs from the 1994 corresponding supplied version, the server SHOULD return an untagged 1995 LIST response with OLDNAME extended data item, with the OLDNAME value 1996 being the supplied existing mailbox name and the name parameter being 1997 the normalized new mailbox name (see Section 6.3.9.7). This would 1998 allow the client to correlate supplied name with the normalized name. 2000 Mailboxes renamed in one IMAP session MAY be announced to other IMAP 2001 sessions using unsolicited LIST response with OLDNAME extended data 2002 item. 2004 In both of the above cases: if the server automatically subscribes a 2005 mailbox when it is renamed, then the unsolicited LIST response for 2006 each affected subscribed mailbox name MUST include the \Subscribed 2007 attribute. No unsolicited LIST responses need to be sent for 2008 children mailboxes, if any. When INBOX is successfully renamed, a 2009 new INBOX is assumed to be created. No unsolicited LIST responses 2010 need to be sent for INBOX in this case. 2012 Examples: C: A682 LIST "" * 2013 S: * LIST () "/" blurdybloop 2014 S: * LIST (\Noselect) "/" foo 2015 S: * LIST () "/" foo/bar 2016 S: A682 OK LIST completed 2017 C: A683 RENAME blurdybloop sarasoop 2018 S: A683 OK RENAME completed 2019 C: A684 RENAME foo zowie 2020 S: A684 OK RENAME Completed 2021 C: A685 LIST "" * 2022 S: * LIST () "/" sarasoop 2023 S: * LIST (\Noselect) "/" zowie 2024 S: * LIST () "/" zowie/bar 2025 S: A685 OK LIST completed 2027 C: Z432 LIST "" * 2028 S: * LIST () "." INBOX 2029 S: * LIST () "." INBOX.bar 2030 S: Z432 OK LIST completed 2031 C: Z433 RENAME INBOX old-mail 2032 S: Z433 OK RENAME completed 2033 C: Z434 LIST "" * 2034 S: * LIST () "." INBOX 2035 S: * LIST () "." INBOX.bar 2036 S: * LIST () "." old-mail 2037 S: Z434 OK LIST completed 2039 Note that renaming a mailbox doesn't update subscription information 2040 on the original name. To keep subscription information in sync, the 2041 following sequence of commands can be used: 2043 C: 1001 RENAME X Y 2044 C: 1002 SUBSCRIBE Y 2045 C: 1003 UNSUBSCRIBE X 2047 Note that the above sequence of commands doesn't account for updating 2048 subscription for any children mailboxes of mailbox X. 2050 6.3.7. SUBSCRIBE Command 2052 Arguments: mailbox 2054 Responses: no specific responses for this command 2055 Result: OK - subscribe completed 2056 NO - subscribe failure: can't subscribe to that name 2057 BAD - command unknown or arguments invalid 2059 The SUBSCRIBE command adds the specified mailbox name to the server's 2060 set of "active" or "subscribed" mailboxes as returned by the LIST 2061 (SUBSCRIBED) command. This command returns a tagged OK response if 2062 the subscription is successful or if the mailbox is already 2063 subscribed. 2065 A server MAY validate the mailbox argument to SUBSCRIBE to verify 2066 that it exists. However, it SHOULD NOT unilaterally remove an 2067 existing mailbox name from the subscription list even if a mailbox by 2068 that name no longer exists. 2070 Note: This requirement is because a server site can choose to 2071 routinely remove a mailbox with a well-known name (e.g., "system- 2072 alerts") after its contents expire, with the intention of 2073 recreating it when new contents are appropriate. 2075 Example: C: A002 SUBSCRIBE #news.comp.mail.mime 2076 S: A002 OK SUBSCRIBE completed 2078 6.3.8. UNSUBSCRIBE Command 2080 Arguments: mailbox name 2082 Responses: no specific responses for this command 2084 Result: OK - unsubscribe completed 2085 NO - unsubscribe failure: can't unsubscribe that name 2086 BAD - command unknown or arguments invalid 2088 The UNSUBSCRIBE command removes the specified mailbox name from the 2089 server's set of "active" or "subscribed" mailboxes as returned by the 2090 LIST (SUBSCRIBED) command. This command returns a tagged OK response 2091 if the unsubscription is successful or if the mailbox is not 2092 subscribed. 2094 Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime 2095 S: A002 OK UNSUBSCRIBE completed 2097 6.3.9. LIST Command 2099 Arguments (basic): reference name 2100 mailbox name with possible wildcards 2102 Arguments (extended): selection options (OPTIONAL) 2103 reference name 2104 mailbox patterns 2105 return options (OPTIONAL) 2107 Responses: untagged responses: LIST 2109 Result: OK - list completed 2110 NO - list failure: can't list that reference or mailbox 2111 name 2112 BAD - command unknown or arguments invalid 2114 The LIST command returns a subset of mailbox names from the complete 2115 set of all mailbox names available to the client. Zero or more 2116 untagged LIST responses are returned, containing the name attributes, 2117 hierarchy delimiter, name, and possible extension information; see 2118 the description of the LIST response (Section 7.3.1) for more detail. 2120 The LIST command SHOULD return its data quickly, without undue delay. 2121 For example, it SHOULD NOT go to excess trouble to calculate the 2122 \Marked or \Unmarked status or perform other processing; if each name 2123 requires 1 second of processing, then a list of 1200 names would take 2124 20 minutes! 2126 The extended LIST command, originally introduced in [RFC5258], 2127 provides capabilities beyond that of the original IMAP LIST command. 2128 The extended syntax is being used if one or more of the following 2129 conditions is true: 2131 1. if the first word after the command name begins with a 2132 parenthesis ("LIST selection options"); 2134 2. if the second word after the command name begins with a 2135 parenthesis; 2137 3. if the LIST command has more than 2 parameters ("LIST return 2138 options") 2140 An empty ("" string) reference name argument indicates that the 2141 mailbox name is interpreted as by SELECT. The returned mailbox names 2142 MUST match the supplied mailbox name pattern(s). A non-empty 2143 reference name argument is the name of a mailbox or a level of 2144 mailbox hierarchy, and indicates the context in which the mailbox 2145 name is interpreted. Clients SHOULD use the empty reference 2146 argument. 2148 In the basic syntax only, an empty ("" string) mailbox name argument 2149 is a special request to return the hierarchy delimiter and the root 2150 name of the name given in the reference. The value returned as the 2151 root MAY be the empty string if the reference is non-rooted or is an 2152 empty string. In all cases, a hierarchy delimiter (or NIL if there 2153 is no hierarchy) is returned. This permits a client to get the 2154 hierarchy delimiter (or find out that the mailbox names are flat) 2155 even when no mailboxes by that name currently exist. 2157 In the extended syntax, any mailbox name arguments that are empty 2158 strings are ignored. There is no special meaning for empty mailbox 2159 names when the extended syntax is used. 2161 The reference and mailbox name arguments are interpreted into a 2162 canonical form that represents an unambiguous left-to-right 2163 hierarchy. The returned mailbox names will be in the interpreted 2164 form, that we call "canonical LIST pattern" later in this document. 2165 To define the term "canonical LIST pattern" formally: it refers to 2166 the canonical pattern constructed internally by the server from the 2167 reference and mailbox name arguments. 2169 Note: The interpretation of the reference argument is 2170 implementation-defined. It depends upon whether the server 2171 implementation has a concept of the "current working directory" 2172 and leading "break out characters", which override the current 2173 working directory. 2175 For example, on a server which exports a UNIX or NT filesystem, 2176 the reference argument contains the current working directory, and 2177 the mailbox name argument would contain the name as interpreted in 2178 the current working directory. 2180 If a server implementation has no concept of break out characters, 2181 the canonical form is normally the reference name appended with 2182 the mailbox name. Note that if the server implements the 2183 namespace convention (Section 5.1.2.1), "#" is a break out 2184 character and must be treated as such. 2186 If the reference argument is not a level of mailbox hierarchy 2187 (that is, it is a \NoInferiors name), and/or the reference 2188 argument does not end with the hierarchy delimiter, it is 2189 implementation-dependent how this is interpreted. For example, a 2190 reference of "foo/bar" and mailbox name of "rag/baz" could be 2191 interpreted as "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/ 2192 baz". A client SHOULD NOT use such a reference argument except at 2193 the explicit request of the user. A hierarchical browser MUST NOT 2194 make any assumptions about server interpretation of the reference 2195 unless the reference is a level of mailbox hierarchy AND ends with 2196 the hierarchy delimiter. 2198 Any part of the reference argument that is included in the 2199 interpreted form SHOULD prefix the interpreted form. It SHOULD also 2200 be in the same form as the reference name argument. This rule 2201 permits the client to determine if the returned mailbox name is in 2202 the context of the reference argument, or if something about the 2203 mailbox argument overrode the reference argument. Without this rule, 2204 the client would have to have knowledge of the server's naming 2205 semantics including what characters are "breakouts" that override a 2206 naming context. 2208 Here are some examples of how references 2209 and mailbox names might be interpreted on a UNIX-based 2210 server: 2212 Reference Mailbox Name Interpretation 2213 ------------ ------------ -------------- 2214 ~smith/Mail/ foo.* ~smith/Mail/foo.* 2215 archive/ % archive/% 2216 #news. comp.mail.* #news.comp.mail.* 2217 ~smith/Mail/ /usr/doc/foo /usr/doc/foo 2218 archive/ ~fred/Mail/* ~fred/Mail/* 2220 The first three examples demonstrate interpretations in 2221 the context of the reference argument. Note that 2222 "~smith/Mail" SHOULD NOT be transformed into something 2223 like "/u2/users/smith/Mail", or it would be impossible 2224 for the client to determine that the interpretation was 2225 in the context of the reference. 2227 The character "*" is a wildcard, and matches zero or more characters 2228 at this position. The character "%" is similar to "*", but it does 2229 not match a hierarchy delimiter. If the "%" wildcard is the last 2230 character of a mailbox name argument, matching levels of hierarchy 2231 are also returned. If these levels of hierarchy are not also 2232 selectable mailboxes, they are returned with the \Noselect mailbox 2233 name attribute (see the description of the LIST response 2234 (Section 7.3.1) for more details). 2236 Any syntactically valid pattern that is not accepted by a server for 2237 any reason MUST be silently ignored. I.e. it results in no LIST 2238 responses and the LIST command still returns tagged OK response. 2240 Selection options tell the server to limit the mailbox names that are 2241 selected by the LIST operation. If selection options are used, the 2242 mailboxes returned are those that match both the list of canonical 2243 LIST patterns and the selection options. Unless a particular 2244 selection option provides special rules, the selection options are 2245 cumulative: a mailbox that matches the mailbox patterns is selected 2246 only if it also matches all of the selection options. (An example of 2247 a selection option with special rules is the RECURSIVEMATCH option.) 2249 Return options control what information is returned for each matched 2250 mailbox. Return options MUST NOT cause the server to report 2251 information about additional mailbox names other than those that 2252 match the canonical LIST patterns and selection options. If no 2253 return options are specified, the client is only expecting 2254 information about mailbox attributes. The server MAY return other 2255 information about the matched mailboxes, and clients MUST be able to 2256 handle that situation. 2258 Initial selection options and return options are defined in the 2259 following subsections, and new ones will also be defined in 2260 extensions. Initial options defined in this document MUST be 2261 supported. Each non-initial option will be enabled by a capability 2262 string (one capability may enable multiple options), and a client 2263 MUST NOT send an option for which the server has not advertised 2264 support. A server MUST respond to options it does not recognize with 2265 a BAD response. The client SHOULD NOT specify any option more than 2266 once; however, if the client does this, the server MUST act as if it 2267 received the option only once. The order in which options are 2268 specified by the client is not significant. 2270 In general, each selection option except RECURSIVEMATCH will have a 2271 corresponding return option with the same name. The REMOTE selection 2272 option is an anomaly in this regard, and does not have a 2273 corresponding return option. That is because it expands, rather than 2274 restricts, the set of mailboxes that are returned. Future extensions 2275 to this specification should keep this parallelism in mind and define 2276 a pair of corresponding selection and return options. 2278 Server implementations are permitted to "hide" otherwise accessible 2279 mailboxes from the wildcard characters, by preventing certain 2280 characters or names from matching a wildcard in certain situations. 2281 For example, a UNIX-based server might restrict the interpretation of 2282 "*" so that an initial "/" character does not match. 2284 The special name INBOX is included in the output from LIST, if INBOX 2285 is supported by this server for this user and if the uppercase string 2286 "INBOX" matches the interpreted reference and mailbox name arguments 2287 with wildcards as described above. The criteria for omitting INBOX 2288 is whether SELECT INBOX will return failure; it is not relevant 2289 whether the user's real INBOX resides on this or some other server. 2291 6.3.9.1. LIST Selection Options 2293 The selection options defined in this specification are as follows: 2295 SUBSCRIBED - causes the LIST command to list subscribed names, 2296 rather than the existing mailboxes. This will often be a subset 2297 of the actual mailboxes. It's also possible for this list to 2298 contain the names of mailboxes that don't exist. In any case, the 2299 list MUST include exactly those mailbox names that match the 2300 canonical list pattern and are subscribed to. 2302 This option defines a mailbox attribute, "\Subscribed", that 2303 indicates that a mailbox name is subscribed to. The "\Subscribed" 2304 attribute MUST be supported and MUST be accurately computed when 2305 the SUBSCRIBED selection option is specified. 2307 Note that the SUBSCRIBED selection option implies the SUBSCRIBED 2308 return option (see below). 2310 REMOTE - causes the LIST command to show remote mailboxes as well as 2311 local ones, as described in [RFC2193]. This option is intended to 2312 replace the RLIST command and, in conjunction with the SUBSCRIBED 2313 selection option, the RLSUB command. Servers that don't support 2314 the concept of remote mailboxes just ignore this option. 2316 This option defines a mailbox attribute, "\Remote", that indicates 2317 that a mailbox is a remote mailbox. The "\Remote" attribute MUST 2318 be accurately computed when the REMOTE option is specified. 2320 The REMOTE selection option has no interaction with other options. 2321 Its effect is to tell the server to apply the other options, if 2322 any, to remote mailboxes, in addition to local ones. In 2323 particular, it has no interaction with RECURSIVEMATCH (see below). 2324 A request for (REMOTE RECURSIVEMATCH) is invalid, because a 2325 request for (RECURSIVEMATCH) is also invalid. A request for 2326 (REMOTE RECURSIVEMATCH SUBSCRIBED) is asking for all subscribed 2327 mailboxes, both local and remote. 2329 RECURSIVEMATCH - this option forces the server to return information 2330 about parent mailboxes that don't match other selection options, 2331 but have some submailboxes that do. Information about children is 2332 returned in the CHILDINFO extended data item, as described in 2333 Section 6.3.9.6. 2335 Note 1: In order for a parent mailbox to be returned, it still has 2336 to match the canonical LIST pattern. 2338 Note 2: When returning the CHILDINFO extended data item, it 2339 doesn't matter whether or not the submailbox matches the canonical 2340 LIST pattern. See also example 9 in Section 6.3.9.8. 2342 The RECURSIVEMATCH option MUST NOT occur as the only selection 2343 option (or only with REMOTE), as it only makes sense when other 2344 selection options are also used. The server MUST return BAD 2345 tagged response in such case. 2347 Note that even if the RECURSIVEMATCH option is specified, the 2348 client MUST still be able to handle a case when a CHILDINFO 2349 extended data item is returned and there are no submailboxes that 2350 meet the selection criteria of the subsequent LIST command, as 2351 they can be deleted/renamed after the LIST response was sent, but 2352 before the client had a chance to access them. 2354 6.3.9.2. LIST Return Options 2356 The return options defined in this specification are as follows: 2358 SUBSCRIBED - causes the LIST command to return subscription state 2359 for all matching mailbox names. The "\Subscribed" attribute MUST 2360 be supported and MUST be accurately computed when the SUBSCRIBED 2361 return option is specified. Further, all other mailbox attributes 2362 MUST be accurately computed (this differs from the behavior of the 2363 obsolete LSUB command from RFC 3501). Note that the above 2364 requirements don't override the requirement for the LIST command 2365 to return results quickly (see Section 6.3.9), i.e. server 2366 implementations need to compute results quickly and accurately. 2367 For example, server implementors might need to create quick access 2368 indices. 2370 CHILDREN - requests mailbox child information as originally proposed 2371 in [RFC3348]. See Section 6.3.9.5, below, for details. 2373 STATUS - requests STATUS response for each matching mailbox. 2375 This option takes STATUS data items as parameters. For each 2376 selectable mailbox matching the list pattern and selection 2377 options, the server MUST return an untagged LIST response 2378 followed by an untagged STATUS response containing the 2379 information requested in the STATUS return option, except for 2380 some cases described below. 2382 If an attempted STATUS for a listed mailbox fails because the 2383 mailbox can't be selected (e.g., if the "l" ACL right [RFC4314] 2384 is granted to the mailbox and the "r" right is not granted, or 2385 due to a race condition between LIST and STATUS changing the 2386 mailbox to \NoSelect), the STATUS response MUST NOT be returned 2387 and the LIST response MUST include the \NoSelect attribute. 2388 This means the server may have to buffer the LIST reply until 2389 it has successfully looked up the necessary STATUS information. 2391 If the server runs into unexpected problems while trying to 2392 look up the STATUS information, it MAY drop the corresponding 2393 STATUS reply. In such a situation, the LIST command would 2394 still return a tagged OK reply. 2396 6.3.9.3. General Principles for Returning LIST Responses 2398 This section outlines several principles that can be used by server 2399 implementations of this document to decide whether a LIST response 2400 should be returned, as well as how many responses and what kind of 2401 information they may contain. 2403 1. At most one LIST response should be returned for each mailbox 2404 name that matches the canonical LIST pattern. Server 2405 implementors must not assume that clients will be able to 2406 assemble mailbox attributes and other information returned in 2407 multiple LIST responses. 2409 2. There are only two reasons for including a matching mailbox name 2410 in the responses to the LIST command (note that the server is 2411 allowed to return unsolicited responses at any time, and such 2412 responses are not governed by this rule): 2414 A. The mailbox name also satisfies the selection criteria. 2416 B. The mailbox name doesn't satisfy the selection criteria, but 2417 it has at least one descendant mailbox name that satisfies 2418 the selection criteria and that doesn't match the canonical 2419 LIST pattern. 2421 For more information on this case, see the CHILDINFO extended 2422 data item described in Section 6.3.9.6. Note that the 2423 CHILDINFO extended data item can only be returned when the 2424 RECURSIVEMATCH selection option is specified. 2426 3. Attributes returned in the same LIST response must be treated 2427 additively. For example, the following response 2429 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2431 means that the "Fruit/Peach" mailbox doesn't exist, but it is 2432 subscribed. 2434 6.3.9.4. Additional LIST-related Requirements on Clients 2436 All clients MUST treat a LIST attribute with a stronger meaning as 2437 implying any attribute that can be inferred from it. (See 2438 Section 7.3.1 for the list of currently defined attributes). For 2439 example, the client must treat the presence of the \NoInferiors 2440 attribute as if the \HasNoChildren attribute was also sent by the 2441 server. 2443 The following table summarizes inference rules. 2445 +--------------------+-------------------+ 2446 | returned attribute | implied attribute | 2447 +--------------------+-------------------+ 2448 | \NoInferiors | \HasNoChildren | 2449 | \NonExistent | \NoSelect | 2450 +--------------------+-------------------+ 2452 6.3.9.5. The CHILDREN Return Option 2454 The CHILDREN return option is simply an indication that the client 2455 wants information about whether or not mailboxes contain children 2456 mailboxes; a server MAY provide it even if the option is not 2457 specified. 2459 Many IMAP4 clients present to the user a hierarchical view of the 2460 mailboxes that a user has access to. Rather than initially 2461 presenting to the user the entire mailbox hierarchy, it is often 2462 preferable to show to the user a collapsed outline list of the 2463 mailbox hierarchy (particularly if there is a large number of 2464 mailboxes). The user can then expand the collapsed outline hierarchy 2465 as needed. It is common to include within the collapsed hierarchy a 2466 visual clue (such as a ''+'') to indicate that there are child 2467 mailboxes under a particular mailbox. When the visual clue is 2468 clicked, the hierarchy list is expanded to show the child mailboxes. 2469 The CHILDREN return option provides a mechanism for a client to 2470 efficiently determine whether a particular mailbox has children, 2471 without issuing a LIST "" * or a LIST "" % for each mailbox name. 2472 The CHILDREN return option defines two new attributes that MUST be 2473 returned within a LIST response: \HasChildren and \HasNoChildren. 2474 Although these attributes MAY be returned in response to any LIST 2475 command, the CHILDREN return option is provided to indicate that the 2476 client particularly wants this information. If the CHILDREN return 2477 option is present, the server MUST return these attributes even if 2478 their computation is expensive. 2480 \HasChildren 2481 The presence of this attribute indicates that the mailbox has 2482 child mailboxes. A server SHOULD NOT set this attribute if 2483 there are child mailboxes and the user does not have permission 2484 to access any of them. In this case, \HasNoChildren SHOULD be 2485 used. In many cases, however, a server may not be able to 2486 efficiently compute whether a user has access to any child 2487 mailbox. Note that even though the \HasChildren attribute for a 2488 mailbox must be correct at the time of processing of the 2489 mailbox, a client must be prepared to deal with a situation when 2490 a mailbox is marked with the \HasChildren attribute, but no 2491 child mailbox appears in the response to the LIST command. This 2492 might happen, for example, due to children mailboxes being 2493 deleted or made inaccessible to the user (using access control) 2494 by another client before the server is able to list them. 2496 \HasNoChildren 2498 The presence of this attribute indicates that the mailbox has NO 2499 child mailboxes that are accessible to the currently 2500 authenticated user. 2502 It is an error for the server to return both a \HasChildren and a 2503 \HasNoChildren attribute in the same LIST response. 2505 Note: the \HasNoChildren attribute should not be confused with the 2506 the \NoInferiors attribute, which indicates that no child mailboxes 2507 exist now and none can be created in the future. 2509 6.3.9.6. CHILDINFO Extended Data Item 2511 The CHILDINFO extended data item MUST NOT be returned unless the 2512 client has specified the RECURSIVEMATCH selection option. 2514 The CHILDINFO extended data item in a LIST response describes the 2515 selection criteria that has caused it to be returned and indicates 2516 that the mailbox has at least one descendant mailbox that matches the 2517 selection criteria. 2519 Note: Some servers allow for mailboxes to exist without requiring 2520 their parent to exist. For example, a mailbox "Customers/ABC" can 2521 exist while the mailbox "Customers" does not. As CHILDINFO extended 2522 data item is not allowed if the RECURSIVEMATCH selection option is 2523 not specified, such servers SHOULD use the "\NonExistent 2524 \HasChildren" attribute pair to signal to the client that there is a 2525 descendant mailbox that matches the selection criteria. See example 2526 11 in Section 6.3.9.8. 2528 The returned selection criteria allow the client to distinguish a 2529 solicited response from an unsolicited one, as well as to distinguish 2530 among solicited responses caused by multiple pipelined LIST commands 2531 that specify different criteria. 2533 Servers SHOULD only return a non-matching mailbox name along with 2534 CHILDINFO if at least one matching child is not also being returned. 2535 That is, servers SHOULD suppress redundant CHILDINFO responses. 2537 Examples 8 and 10 in Section 6.3.9.8 demonstrate the difference 2538 between present CHILDINFO extended data item and the "\HasChildren" 2539 attribute. 2541 The following table summarizes interaction between the "\NonExistent" 2542 attribute and CHILDINFO (the first column indicates whether the 2543 parent mailbox exists): 2545 +--------+-------------+------------------+-------------------------+ 2546 | exists | meets the | has a child that | returned | 2547 | | selection | meets the | IMAP4rev2/LIST-EXTENDED | 2548 | | criteria | selection | attributes and | 2549 | | | criteria | CHILDINFO | 2550 +--------+-------------+------------------+-------------------------+ 2551 | no | no | no | no LIST response | 2552 | | | | returned | 2553 | yes | no | no | no LIST response | 2554 | | | | returned | 2555 | no | yes | no | (\NonExistent ) | 2556 | yes | yes | no | () | 2557 | no | no | yes | (\NonExistent) + | 2558 | | | | CHILDINFO | 2559 | yes | no | yes | () + CHILDINFO | 2560 | no | yes | yes | (\NonExistent ) + | 2561 | | | | CHILDINFO | 2562 | yes | yes | yes | () + CHILDINFO | 2563 +--------+-------------+------------------+-------------------------+ 2565 where is one or more attributes that correspond to the 2566 selection criteria; for example, for the SUBSCRIBED option the 2567 is \Subscribed. 2569 6.3.9.7. OLDNAME Extended Data Item 2571 The OLDNAME extended data item is included when a mailbox name is 2572 created (with CREATE command), renamed (with RENAME command) or 2573 deleted (with DELETE command). (When a mailbox is deleted the 2574 "\NonExistent" attribute is also included.) IMAP extensions can 2575 specify other conditions when OLDNAME extended data item should be 2576 included. 2578 If the server allows de-normalized mailbox names (see Section 5.1) in 2579 SELECT/EXAMINE, CREATE, RENAME or DELETE, it SHOULD return an 2580 unsolicited LIST response that includes OLDNAME extended data item, 2581 whenever the supplied mailbox name differs from the resulting 2582 normalized mailbox name. From the client point of view this is 2583 indistinguishable from another user renaming or deleting the mailbox, 2584 as specified in the previous paragraph. 2586 A deleted mailbox can be announced like this: 2588 S: * LIST (\NonExistent) "." "INBOX.DeletedMailbox" 2590 Example of a renamed mailbox: 2592 S: * LIST () "/" "NewMailbox" ("OLDNAME" ("OldMailbox")) 2594 6.3.9.8. LIST Command Examples 2596 This example shows some uses of the basic LIST command: 2598 Example: C: A101 LIST "" "" 2599 S: * LIST (\Noselect) "/" "" 2600 S: A101 OK LIST Completed 2601 C: A102 LIST #news.comp.mail.misc "" 2602 S: * LIST (\Noselect) "." #news. 2603 S: A102 OK LIST Completed 2604 C: A103 LIST /usr/staff/jones "" 2605 S: * LIST (\Noselect) "/" / 2606 S: A103 OK LIST Completed 2607 C: A202 LIST ~/Mail/ % 2608 S: * LIST (\Noselect) "/" ~/Mail/foo 2609 S: * LIST () "/" ~/Mail/meetings 2610 S: A202 OK LIST completed 2612 Extended examples: 2614 1: The first example shows the complete local hierarchy that will 2615 be used for the other examples. 2617 C: A01 LIST "" "*" 2618 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2619 S: * LIST () "/" "Fruit" 2620 S: * LIST () "/" "Fruit/Apple" 2621 S: * LIST () "/" "Fruit/Banana" 2622 S: * LIST () "/" "Tofu" 2623 S: * LIST () "/" "Vegetable" 2624 S: * LIST () "/" "Vegetable/Broccoli" 2625 S: * LIST () "/" "Vegetable/Corn" 2626 S: A01 OK done 2628 2: In the next example, we will see the subscribed mailboxes. This 2629 is similar to, but not equivalent with now deprecated, (see [RFC3501] for more details on LSUB command). Note 2631 that the mailbox called "Fruit/Peach" is subscribed to, but does 2632 not actually exist (perhaps it was deleted while still 2633 subscribed). The "Fruit" mailbox is not subscribed to, but it 2634 has two subscribed children. The "Vegetable" mailbox is 2635 subscribed and has two children; one of them is subscribed as 2636 well. 2638 C: A02 LIST (SUBSCRIBED) "" "*" 2639 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2640 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2641 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2642 S: * LIST (\Subscribed) "/" "Vegetable" 2643 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2644 S: A02 OK done 2646 3: The next example shows the use of the CHILDREN option. The 2647 client, without having to list the second level of hierarchy, 2648 now knows which of the top-level mailboxes have submailboxes 2649 (children) and which do not. Note that it's not necessary for 2650 the server to return the \HasNoChildren attribute for the inbox, 2651 because the \NoInferiors attribute already implies that, and has 2652 a stronger meaning. 2654 C: A03 LIST () "" "%" RETURN (CHILDREN) 2655 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2656 S: * LIST (\HasChildren) "/" "Fruit" 2657 S: * LIST (\HasNoChildren) "/" "Tofu" 2658 S: * LIST (\HasChildren) "/" "Vegetable" 2659 S: A03 OK done 2661 4: In this example, we see more mailboxes that reside on another 2662 server. This is similar to the command . 2664 C: A04 LIST (REMOTE) "" "%" RETURN (CHILDREN) 2665 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2666 S: * LIST (\HasChildren) "/" "Fruit" 2667 S: * LIST (\HasNoChildren) "/" "Tofu" 2668 S: * LIST (\HasChildren) "/" "Vegetable" 2669 S: * LIST (\Remote) "/" "Bread" 2670 S: * LIST (\HasChildren \Remote) "/" "Meat" 2671 S: A04 OK done 2673 5: The following example also requests the server to include 2674 mailboxes that reside on another server. The server returns 2675 information about all mailboxes that are subscribed. This is 2676 similar to the command (see [RFC2193] for more 2677 details on RLSUB). We also see the use of two selection 2678 options. 2680 C: A05 LIST (REMOTE SUBSCRIBED) "" "*" 2681 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2682 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2683 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2684 S: * LIST (\Subscribed) "/" "Vegetable" 2685 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2686 S: * LIST (\Remote \Subscribed) "/" "Bread" 2687 S: A05 OK done 2689 6: The following example requests the server to include mailboxes 2690 that reside on another server. The server is asked to return 2691 subscription information for all returned mailboxes. This is 2692 different from the example above. 2694 Note that the output of this command is not a superset of the 2695 output in the previous example, as it doesn't include LIST 2696 response for the non-existent "Fruit/Peach". 2698 C: A06 LIST (REMOTE) "" "*" RETURN (SUBSCRIBED) 2699 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2700 S: * LIST () "/" "Fruit" 2701 S: * LIST () "/" "Fruit/Apple" 2702 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2703 S: * LIST () "/" "Tofu" 2704 S: * LIST (\Subscribed) "/" "Vegetable" 2705 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2706 S: * LIST () "/" "Vegetable/Corn" 2707 S: * LIST (\Remote \Subscribed) "/" "Bread" 2708 S: * LIST (\Remote) "/" "Meat" 2709 S: A06 OK done 2711 7: The following example demonstrates the difference between the 2712 \HasChildren attribute and the CHILDINFO extended data item. 2714 Let's assume there is the following hierarchy: 2716 C: C01 LIST "" "*" 2717 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2718 S: * LIST () "/" "Foo" 2719 S: * LIST () "/" "Foo/Bar" 2720 S: * LIST () "/" "Foo/Baz" 2721 S: * LIST () "/" "Moo" 2722 S: C01 OK done 2724 If the client asks RETURN (CHILDREN), it will get this: 2726 C: CA3 LIST "" "%" RETURN (CHILDREN) 2727 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2728 S: * LIST (\HasChildren) "/" "Foo" 2729 S: * LIST (\HasNoChildren) "/" "Moo" 2730 S: CA3 OK done 2732 A) Let's also assume that the mailbox "Foo/Baz" is the only 2733 subscribed mailbox. Then we get this result: 2735 C: C02 LIST (SUBSCRIBED) "" "*" 2736 S: * LIST (\Subscribed) "/" "Foo/Baz" 2737 S: C02 OK done 2739 Now, if the client issues , the server 2740 will return no mailboxes (as the mailboxes "Moo", "Foo", and 2741 "Inbox" are NOT subscribed). However, if the client issues 2742 this: 2744 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2745 S: * LIST () "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2746 S: C04 OK done 2748 (i.e., the mailbox "Foo" is not subscribed, but it has a child 2749 that is.) 2751 A1) If the mailbox "Foo" had also been subscribed, the last 2752 command would return this: 2754 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2755 S: * LIST (\Subscribed) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2756 S: C04 OK done 2758 or even this: 2760 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2761 S: * LIST (\Subscribed \HasChildren) "/" "Foo" ("CHILDINFO" 2762 ("SUBSCRIBED")) 2763 S: C04 OK done 2765 A2) If we assume instead that the mailbox "Foo" is not part of 2766 the original hierarchy and is not subscribed, the last command 2767 will give this result: 2769 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2770 S: * LIST (\NonExistent) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2771 S: C04 OK done 2773 B) Now, let's assume that no mailbox is subscribed. In this 2774 case, the command will 2775 return no responses, as there are no subscribed children (even 2776 though "Foo" has children). 2778 C) And finally, suppose that only the mailboxes "Foo" and "Moo" 2779 are subscribed. In that case, we see this result: 2781 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" RETURN (CHILDREN) 2782 S: * LIST (\HasChildren \Subscribed) "/" "Foo" 2783 S: * LIST (\HasNoChildren \Subscribed) "/" "Moo" 2784 S: C04 OK done 2786 (which means that the mailbox "Foo" has children, but none of 2787 them is subscribed). 2789 8: The following example demonstrates that the CHILDINFO extended 2790 data item is returned whether or not children mailboxes match 2791 the canonical LIST pattern. 2793 Let's assume there is the following hierarchy: 2795 C: D01 LIST "" "*" 2796 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2797 S: * LIST () "/" "foo2" 2798 S: * LIST () "/" "foo2/bar1" 2799 S: * LIST () "/" "foo2/bar2" 2800 S: * LIST () "/" "baz2" 2801 S: * LIST () "/" "baz2/bar2" 2802 S: * LIST () "/" "baz2/bar22" 2803 S: * LIST () "/" "baz2/bar222" 2804 S: * LIST () "/" "eps2" 2805 S: * LIST () "/" "eps2/mamba" 2806 S: * LIST () "/" "qux2/bar2" 2807 S: D01 OK done 2808 And that the following mailboxes are subscribed: 2810 C: D02 LIST (SUBSCRIBED) "" "*" 2811 S: * LIST (\Subscribed) "/" "foo2/bar1" 2812 S: * LIST (\Subscribed) "/" "foo2/bar2" 2813 S: * LIST (\Subscribed) "/" "baz2/bar2" 2814 S: * LIST (\Subscribed) "/" "baz2/bar22" 2815 S: * LIST (\Subscribed) "/" "baz2/bar222" 2816 S: * LIST (\Subscribed) "/" "eps2" 2817 S: * LIST (\Subscribed) "/" "eps2/mamba" 2818 S: * LIST (\Subscribed) "/" "qux2/bar2" 2819 S: D02 OK done 2821 The client issues the following command first: 2823 C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*2" 2824 S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED")) 2825 S: * LIST (\Subscribed) "/" "foo2/bar2" 2826 S: * LIST (\Subscribed) "/" "baz2/bar2" 2827 S: * LIST (\Subscribed) "/" "baz2/bar22" 2828 S: * LIST (\Subscribed) "/" "baz2/bar222" 2829 S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED")) 2830 S: * LIST (\Subscribed) "/" "qux2/bar2" 2831 S: D03 OK done 2833 and the server may also include (but this would violate a SHOULD 2834 NOT in Section 3.5, because CHILDINFO is redundant) 2836 S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED")) 2837 S: * LIST (\NonExistent) "/" "qux2" ("CHILDINFO" ("SUBSCRIBED")) 2839 The CHILDINFO extended data item is returned for mailboxes 2840 "foo2", "baz2", and "eps2", because all of them have subscribed 2841 children, even though for the mailbox "foo2" only one of the two 2842 subscribed children matches the pattern, for the mailbox "baz2" 2843 all the subscribed children match the pattern, and for the 2844 mailbox "eps2" none of the subscribed children matches the 2845 pattern. 2847 Note that if the client issues 2849 C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*" 2850 S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED")) 2851 S: * LIST (\Subscribed) "/" "foo2/bar1" 2852 S: * LIST (\Subscribed) "/" "foo2/bar2" 2853 S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED")) 2854 S: * LIST (\Subscribed) "/" "baz2/bar2" 2855 S: * LIST (\Subscribed) "/" "baz2/bar22" 2856 S: * LIST (\Subscribed) "/" "baz2/bar222" 2857 S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED")) 2858 S: * LIST (\Subscribed) "/" "eps2/mamba" 2859 S: * LIST (\Subscribed) "/" "qux2/bar2" 2860 S: D03 OK done 2862 The LIST responses for mailboxes "foo2", "baz2", and "eps2" 2863 still have the CHILDINFO extended data item, even though this 2864 information is redundant and the client can determine it by 2865 itself. 2867 9: The following example shows usage of extended syntax for mailbox 2868 pattern. It also demonstrates that the presence of the 2869 CHILDINFO extended data item doesn't necessarily imply 2870 \HasChildren. 2872 C: a1 LIST "" ("foo") 2873 S: * LIST () "/" foo 2874 S: a1 OK done 2876 C: a2 LIST (SUBSCRIBED) "" "foo/*" 2877 S: * LIST (\Subscribed \NonExistent) "/" foo/bar 2878 S: a2 OK done 2880 C: a3 LIST (SUBSCRIBED RECURSIVEMATCH) "" foo RETURN (CHILDREN) 2881 S: * LIST (\HasNoChildren) "/" foo ("CHILDINFO" ("SUBSCRIBED")) 2882 S: a3 OK done 2884 10: The following example shows how a server that supports missing 2885 mailbox hierarchy elements can signal to a client that didn't 2886 specify the RECURSIVEMATCH selection option that there is a 2887 child mailbox that matches the selection criteria. 2889 C: a1 LIST (REMOTE) "" * 2890 S: * LIST () "/" music/rock 2891 S: * LIST (\Remote) "/" also/jazz 2892 S: a1 OK done 2894 C: a2 LIST () "" % 2895 S: * LIST (\NonExistent \HasChildren) "/" music 2896 S: a2 OK done 2898 C: a3 LIST (REMOTE) "" % 2899 S: * LIST (\NonExistent \HasChildren) "/" music 2900 S: * LIST (\NonExistent \HasChildren) "/" also 2901 S: a3 OK done 2903 C: a3.1 LIST "" (% music/rock) 2904 S: * LIST () "/" music/rock 2905 S: a3.1 OK done 2907 Because "music/rock" is the only mailbox under "music", there's 2908 no need for the server to also return "music". However clients 2909 must handle both cases. 2911 11: The following examples show use of STATUS return option. 2913 C: A01 LIST "" % RETURN (STATUS (MESSAGES UNSEEN)) 2914 S: * LIST () "." "INBOX" 2915 S: * STATUS "INBOX" (MESSAGES 17 UNSEEN 16) 2916 S: * LIST () "." "foo" 2917 S: * STATUS "foo" (MESSAGES 30 UNSEEN 29) 2918 S: * LIST (\NoSelect) "." "bar" 2919 S: A01 OK List completed. 2921 The "bar" mailbox isn't selectable, so it has no STATUS reply. 2923 C: A02 LIST (SUBSCRIBED RECURSIVEMATCH) "" % RETURN (STATUS 2924 (MESSAGES)) 2925 S: * LIST (\Subscribed) "." "INBOX" 2926 S: * STATUS "INBOX" (MESSAGES 17) 2927 S: * LIST () "." "foo" (CHILDINFO ("SUBSCRIBED")) 2928 S: A02 OK List completed. 2930 The LIST reply for "foo" is returned because it has matching 2931 children, but no STATUS reply is returned because "foo" itself 2932 doesn't match the selection criteria. 2934 6.3.10. NAMESPACE Command 2936 Arguments: none 2938 Responses: REQUIRED untagged responses: NAMESPACE 2940 Result: OK - command completed 2941 NO - Can't complete the command 2942 BAD - arguments invalid 2944 The NAMESPACE command causes a single untagged NAMESPACE response to 2945 be returned. The untagged NAMESPACE response contains the prefix and 2946 hierarchy delimiter to the server's Personal Namespace(s), Other 2947 Users' Namespace(s), and Shared Namespace(s) that the server wishes 2948 to expose. The response will contain a NIL for any namespace class 2949 that is not available. The namespace-response-extensions ABNF non 2950 terminal is defined for extensibility and MAY be included in the 2951 NAMESPACE response. 2953 Example 1: 2955 In this example a server supports a single personal namespace. No 2956 leading prefix is used on personal mailboxes and "/" is the hierarchy 2957 delimiter. 2959 C: A001 NAMESPACE 2960 S: * NAMESPACE (("" "/")) NIL NIL 2961 S: A001 OK NAMESPACE command completed 2963 Example 2: 2965 A user logged on anonymously to a server. No personal mailboxes are 2966 associated with the anonymous user and the user does not have access 2967 to the Other Users' Namespace. No prefix is required to access 2968 shared mailboxes and the hierarchy delimiter is "." 2970 C: A001 NAMESPACE 2971 S: * NAMESPACE NIL NIL (("" ".")) 2972 S: A001 OK NAMESPACE command completed 2974 Example 3: 2976 A server that contains a Personal Namespace and a single Shared 2977 Namespace. 2979 C: A001 NAMESPACE 2980 S: * NAMESPACE (("" "/")) NIL (("Public Folders/" "/")) 2981 S: A001 OK NAMESPACE command completed 2983 Example 4: 2985 A server that contains a Personal Namespace, Other Users' Namespace 2986 and multiple Shared Namespaces. Note that the hierarchy delimiter 2987 used within each namespace can be different. 2989 C: A001 NAMESPACE 2990 S: * NAMESPACE (("" "/")) (("~" "/")) (("#shared/" "/") 2991 ("#public/" "/")("#ftp/" "/")("#news." ".")) 2992 S: A001 OK NAMESPACE command completed 2994 The prefix string allows a client to do things such as automatically 2995 creating personal mailboxes or LISTing all available mailboxes within 2996 a namespace. 2998 Example 5: 3000 A server that supports only the Personal Namespace, with a leading 3001 prefix of INBOX to personal mailboxes and a hierarchy delimiter of 3002 "." 3004 C: A001 NAMESPACE 3005 S: * NAMESPACE (("INBOX." ".")) NIL NIL 3006 S: A001 OK NAMESPACE command completed 3008 < Automatically create a mailbox to store sent items.> 3010 C: A002 CREATE "INBOX.Sent Mail" 3011 S: A002 OK CREATE command completed 3013 Although typically a server will support only a single Personal 3014 Namespace, and a single Other User's Namespace, circumstances exist 3015 where there MAY be multiples of these, and a client MUST be prepared 3016 for them. If a client is configured such that it is required to 3017 create a certain mailbox, there can be circumstances where it is 3018 unclear which Personal Namespaces it should create the mailbox in. 3019 In these situations a client SHOULD let the user select which 3020 namespaces to create the mailbox in or just use the first personal 3021 namespace. 3023 Example 6: 3025 In this example, a server supports two Personal Namespaces. In 3026 addition to the regular Personal Namespace, the user has an 3027 additional personal namespace to allow access to mailboxes in an MH 3028 format mailstore. 3030 The client is configured to save a copy of all mail sent by the user 3031 into a mailbox called 'Sent Mail'. Furthermore, after a message is 3032 deleted from a mailbox, the client is configured to move that message 3033 to a mailbox called 'Deleted Items'. 3035 Note that this example demonstrates how some extension parameters can 3036 be passed to further describe the #mh namespace. See the fictitious 3037 "X-PARAM" extension parameter. 3039 C: A001 NAMESPACE 3040 S: * NAMESPACE (("" "/")("#mh/" "/" "X-PARAM" 3041 ("FLAG1" "FLAG2"))) NIL NIL 3042 S: A001 OK NAMESPACE command completed 3044 < It is desired to keep only one copy of sent mail. 3045 It is unclear which Personal Namespace the client 3046 should use to create the 'Sent Mail' mailbox. 3047 The user is prompted to select a namespace and only 3048 one 'Sent Mail' mailbox is created. > 3050 C: A002 CREATE "Sent Mail" 3051 S: A002 OK CREATE command completed 3053 < The client is designed so that it keeps two 3054 'Deleted Items' mailboxes, one for each namespace. > 3056 C: A003 CREATE "Delete Items" 3057 S: A003 OK CREATE command completed 3059 C: A004 CREATE "#mh/Deleted Items" 3060 S: A004 OK CREATE command completed 3062 The next level of hierarchy following the Other Users' Namespace 3063 prefix SHOULD consist of , where is a user name 3064 as per the LOGIN or AUTHENTICATE command. 3066 A client can construct a LIST command by appending a "%" to the Other 3067 Users' Namespace prefix to discover the Personal Namespaces of other 3068 users that are available to the currently authenticated user. 3070 In response to such a LIST command, a server SHOULD NOT return user 3071 names that have not granted access to their personal mailboxes to the 3072 user in question. 3074 A server MAY return a LIST response containing only the names of 3075 users that have explicitly granted access to the user in question. 3077 Alternatively, a server MAY return NO to such a LIST command, 3078 requiring that a user name be included with the Other Users' 3079 Namespace prefix before listing any other user's mailboxes. 3081 Example 7: 3083 A server that supports providing a list of other user's mailboxes 3084 that are accessible to the currently logged on user. 3086 C: A001 NAMESPACE 3087 S: * NAMESPACE (("" "/")) (("Other Users/" "/")) NIL 3088 S: A001 OK NAMESPACE command completed 3090 C: A002 LIST "" "Other Users/%" 3091 S: * LIST () "/" "Other Users/Mike" 3092 S: * LIST () "/" "Other Users/Karen" 3093 S: * LIST () "/" "Other Users/Matthew" 3094 S: * LIST () "/" "Other Users/Tesa" 3095 S: A002 OK LIST command completed 3097 Example 8: 3099 A server that does not support providing a list of other user's 3100 mailboxes that are accessible to the currently logged on user. The 3101 mailboxes are listable if the client includes the name of the other 3102 user with the Other Users' Namespace prefix. 3104 C: A001 NAMESPACE 3105 S: * NAMESPACE (("" "/")) (("#Users/" "/")) NIL 3106 S: A001 OK NAMESPACE command completed 3108 < In this example, the currently logged on user has access to 3109 the Personal Namespace of user Mike, but the server chose to 3110 suppress this information in the LIST response. However, 3111 by appending the user name Mike (received through user input) 3112 to the Other Users' Namespace prefix, the client is able 3113 to get a listing of the personal mailboxes of user Mike. > 3115 C: A002 LIST "" "#Users/%" 3116 S: A002 NO The requested item could not be found. 3118 C: A003 LIST "" "#Users/Mike/%" 3119 S: * LIST () "/" "#Users/Mike/INBOX" 3120 S: * LIST () "/" "#Users/Mike/Foo" 3121 S: A003 OK LIST command completed. 3123 A prefix string might not contain a hierarchy delimiter, because in 3124 some cases it is not needed as part of the prefix. 3126 Example 9: 3128 A server that allows access to the Other Users' Namespace by 3129 prefixing the others' mailboxes with a '~' followed by , 3130 where is a user name as per the LOGIN or AUTHENTICATE 3131 command. 3133 C: A001 NAMESPACE 3134 S: * NAMESPACE (("" "/")) (("~" "/")) NIL 3135 S: A001 OK NAMESPACE command completed 3137 < List the mailboxes for user mark > 3139 C: A002 LIST "" "~mark/%" 3140 S: * LIST () "/" "~mark/INBOX" 3141 S: * LIST () "/" "~mark/foo" 3142 S: A002 OK LIST command completed 3144 6.3.11. STATUS Command 3146 Arguments: mailbox name 3147 status data item names 3149 Responses: REQUIRED untagged responses: STATUS 3151 Result: OK - status completed 3152 NO - status failure: no status for that name 3153 BAD - command unknown or arguments invalid 3155 The STATUS command requests the status of the indicated mailbox. It 3156 does not change the currently selected mailbox, nor does it affect 3157 the state of any messages in the queried mailbox. 3159 The STATUS command provides an alternative to opening a second 3160 IMAP4rev2 connection and doing an EXAMINE command on a mailbox to 3161 query that mailbox's status without deselecting the current mailbox 3162 in the first IMAP4rev2 connection. 3164 Unlike the LIST command, the STATUS command is not guaranteed to be 3165 fast in its response. Under certain circumstances, it can be quite 3166 slow. In some implementations, the server is obliged to open the 3167 mailbox read-only internally to obtain certain status information. 3168 Also unlike the LIST command, the STATUS command does not accept 3169 wildcards. 3171 Note: The STATUS command is intended to access the status of 3172 mailboxes other than the currently selected mailbox. Because the 3173 STATUS command can cause the mailbox to be opened internally, and 3174 because this information is available by other means on the 3175 selected mailbox, the STATUS command SHOULD NOT be used on the 3176 currently selected mailbox. However, servers MUST be able to 3177 execute STATUS command on the selected mailbox. (This might also 3178 implicitly happen when STATUS return option is used in a LIST 3179 command). 3181 The STATUS command MUST NOT be used as a "check for new messages 3182 in the selected mailbox" operation (refer to Section 7 and 3183 Section 7.4.1 for more information about the proper method for new 3184 message checking). 3186 STATUS SIZE (see below) can take a significant amount of time, 3187 depending upon server implementation. Clients should use STATUS 3188 SIZE cautiously. 3190 The currently defined status data items that can be requested are: 3192 MESSAGES The number of messages in the mailbox. 3194 UIDNEXT The next unique identifier value of the mailbox. Refer to 3195 Section 2.3.1.1 for more information. 3197 UIDVALIDITY The unique identifier validity value of the mailbox. 3198 Refer to Section 2.3.1.1 for more information. 3200 UNSEEN The number of messages which do not have the \Seen flag set. 3202 DELETED The number of messages which have the \Deleted flag set. 3204 SIZE The total size of the mailbox in octets. This is not strictly 3205 required to be an exact value, but it MUST be equal to or greater 3206 than the sum of the values of the RFC822.SIZE FETCH message data 3207 items (see Section 6.4.5) of all messages in the mailbox. 3209 Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES) 3210 S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292) 3211 S: A042 OK STATUS completed 3213 6.3.12. APPEND Command 3215 Arguments: mailbox name 3216 OPTIONAL flag parenthesized list 3217 OPTIONAL date/time string 3218 message literal 3220 Responses: OPTIONAL untagged response: LIST 3221 Result: OK - append completed 3222 NO - append error: can't append to that mailbox, error 3223 in flags or date/time or message text 3224 BAD - command unknown or arguments invalid 3226 The APPEND command appends the literal argument as a new message to 3227 the end of the specified destination mailbox. This argument SHOULD 3228 be in the format of an [RFC-5322] or [I18N-HDRS] message. 8-bit 3229 characters are permitted in the message. A server implementation 3230 that is unable to preserve 8-bit data properly MUST be able to 3231 reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB] 3232 content transfer encoding. 3234 Note: There may be exceptions, e.g., draft messages, in which 3235 required [RFC-5322] header fields are omitted in the message 3236 literal argument to APPEND. The full implications of doing so 3237 must be understood and carefully weighed. 3239 If a flag parenthesized list is specified, the flags SHOULD be set in 3240 the resulting message; otherwise, the flag list of the resulting 3241 message is set to empty by default. 3243 If a date-time is specified, the internal date SHOULD be set in the 3244 resulting message; otherwise, the internal date of the resulting 3245 message is set to the current date and time by default. 3247 If the append is unsuccessful for any reason, the mailbox MUST be 3248 restored to its state before the APPEND attempt (other than possibly 3249 keeping the changed mailbox's UIDNEXT value); no partial appending is 3250 permitted. 3252 If the destination mailbox does not exist, a server MUST return an 3253 error, and MUST NOT automatically create the mailbox. Unless it is 3254 certain that the destination mailbox can not be created, the server 3255 MUST send the response code "[TRYCREATE]" as the prefix of the text 3256 of the tagged NO response. This gives a hint to the client that it 3257 can attempt a CREATE command and retry the APPEND if the CREATE is 3258 successful. 3260 On successful completion of an APPEND, the server returns an 3261 APPENDUID response code (see Section 7.1), unless specified otherwise 3262 below. 3264 In the case of a mailbox that has permissions set so that the client 3265 can APPEND to the mailbox, but not SELECT or EXAMINE it, the server 3266 MUST NOT send an APPENDUID response code as it would disclose 3267 information about the mailbox. 3269 In the case of a mailbox that has UIDNOTSTICKY status (see 3270 Section 7.1), the server MAY omit the APPENDUID response code as it 3271 is not meaningful. 3273 If the mailbox is currently selected, the normal new message actions 3274 SHOULD occur. Specifically, the server SHOULD notify the client 3275 immediately via an untagged EXISTS response. If the server does not 3276 do so, the client MAY issue a NOOP command after one or more APPEND 3277 commands. 3279 If the server decides to convert (normalize) the mailbox name, it 3280 SHOULD return an untagged LIST with OLDNAME extended data item, with 3281 the OLDNAME value being the supplied mailbox name and the name 3282 parameter being the normalized mailbox name. (See Section 6.3.9.7 3283 for more details.) 3285 Example: C: A003 APPEND saved-messages (\Seen) {310} 3286 S: + Ready for literal data 3287 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) 3288 C: From: Fred Foobar 3289 C: Subject: afternoon meeting 3290 C: To: mooch@owatagu.siam.edu 3291 C: Message-Id: 3292 C: MIME-Version: 1.0 3293 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 3294 C: 3295 C: Hello Joe, do you think we can meet at 3:30 tomorrow? 3296 C: 3297 S: A003 OK APPEND completed 3299 Example: C: A003 APPEND saved-messages (\Seen) {297} 3300 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) 3301 C: From: Fred Foobar 3302 C: Subject: afternoon meeting 3303 C: To: mooch@example.com 3304 C: Message-Id: 3305 C: MIME-Version: 1.0 3306 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 3307 C: 3308 C: Hello Joe, do you think we can meet at 3:30 tomorrow? 3309 C: 3310 S: A003 OK [APPENDUID 38505 3955] APPEND completed 3311 C: A004 COPY 2:4 meeting 3312 S: A004 OK [COPYUID 38505 304,319:320 3956:3958] Done 3313 C: A005 UID COPY 305:310 meeting 3314 S: A005 OK No matching messages, so nothing copied 3315 C: A006 COPY 2 funny 3316 S: A006 OK Done 3317 C: A007 SELECT funny 3318 S: * 1 EXISTS 3319 S: * OK [UIDVALIDITY 3857529045] Validity session-only 3320 S: * OK [UIDNEXT 2] Predicted next UID 3321 S: * NO [UIDNOTSTICKY] Non-persistent UIDs 3322 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 3323 S: * OK [PERMANENTFLAGS (\Deleted \Seen)] Limited 3324 S: * LIST () "." funny 3325 S: A007 OK [READ-WRITE] SELECT completed 3327 In this example, A003 and A004 demonstrate successful appending and 3328 copying to a mailbox that returns the UIDs assigned to the messages. 3329 A005 is an example in which no messages were copied; this is because 3330 in A003, we see that message 2 had UID 304, and message 3 had UID 3331 319; therefore, UIDs 305 through 310 do not exist (refer to 3332 Section 2.3.1.1 for further explanation). A006 is an example of a 3333 message being copied that did not return a COPYUID; and, as expected, 3334 A007 shows that the mail store containing that mailbox does not 3335 support persistent UIDs. 3337 Note: The APPEND command is not used for message delivery, because 3338 it does not provide a mechanism to transfer [SMTP] envelope 3339 information. 3341 6.3.13. IDLE Command 3343 Arguments: none 3345 Responses: continuation data will be requested; the client sends the 3346 continuation data "DONE" to end the command 3348 Result: OK - IDLE completed after client sent "DONE" 3349 NO - failure: the server will not allow the IDLE command 3350 at this time 3351 BAD - command unknown or arguments invalid 3353 Without the IDLE command a client would need to poll the server for 3354 changes to the selected mailbox (new mail, deletions, flag changes). 3355 It's often more desirable to have the server transmit updates to the 3356 client in real time. This allows a user to see new mail immediately. 3357 The IDLE command allows a client to tell the server that it's ready 3358 to accept such real-time updates. 3360 The IDLE command is sent from the client to the server when the 3361 client is ready to accept unsolicited update messages. The server 3362 requests a response to the IDLE command using the continuation ("+") 3363 response. The IDLE command remains active until the client responds 3364 to the continuation, and as long as an IDLE command is active, the 3365 server is now free to send untagged EXISTS, EXPUNGE, FETCH, and other 3366 responses at any time. If the server chooses to send unsolicited 3367 FETCH responses, they MUST include UID FETCH item. 3369 The IDLE command is terminated by the receipt of a "DONE" 3370 continuation from the client; such response satisfies the server's 3371 continuation request. At that point, the server MAY send any 3372 remaining queued untagged responses and then MUST immediately send 3373 the tagged response to the IDLE command and prepare to process other 3374 commands. As for other commands, the processing of any new command 3375 may cause the sending of unsolicited untagged responses, subject to 3376 the ambiguity limitations. The client MUST NOT send a command while 3377 the server is waiting for the DONE, since the server will not be able 3378 to distinguish a command from a continuation. 3380 The server MAY consider a client inactive if it has an IDLE command 3381 running, and if such a server has an inactivity timeout it MAY log 3382 the client off implicitly at the end of its timeout period. Because 3383 of that, clients using IDLE are advised to terminate the IDLE and re- 3384 issue it at least every 29 minutes to avoid being logged off. This 3385 still allows a client to receive immediate mailbox updates even 3386 though it need only "poll" at half hour intervals. 3388 Example: C: A001 SELECT INBOX 3389 S: * FLAGS (\Deleted \Seen \Flagged) 3390 S: * OK [PERMANENTFLAGS (\Deleted \Seen \Flagged)] Limited 3391 S: * 3 EXISTS 3392 S: * OK [UIDVALIDITY 1] 3393 S: * LIST () "/" INBOX 3394 S: A001 OK [READ-WRITE] SELECT completed 3395 C: A002 IDLE 3396 S: + idling 3397 ...time passes; new mail arrives... 3398 S: * 4 EXISTS 3399 C: DONE 3400 S: A002 OK IDLE terminated 3401 ...another client expunges message 2 now... 3402 C: A003 FETCH 4 ALL 3403 S: * 4 FETCH (...) 3404 S: A003 OK FETCH completed 3405 C: A004 IDLE 3406 S: * 2 EXPUNGE 3407 S: * 3 EXISTS 3408 S: + idling 3409 ...time passes; another client expunges message 3... 3410 S: * 3 EXPUNGE 3411 S: * 2 EXISTS 3412 ...time passes; new mail arrives... 3413 S: * 3 EXISTS 3414 C: DONE 3415 S: A004 OK IDLE terminated 3416 C: A005 FETCH 3 ALL 3417 S: * 3 FETCH (...) 3418 S: A005 OK FETCH completed 3419 C: A006 IDLE 3421 6.4. Client Commands - Selected State 3423 In the selected state, commands that manipulate messages in a mailbox 3424 are permitted. 3426 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 3427 and the authenticated state commands (SELECT, EXAMINE, NAMESPACE, 3428 CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, STATUS, and 3429 APPEND), the following commands are valid in the selected state: 3430 CLOSE, UNSELECT, EXPUNGE, SEARCH, FETCH, STORE, COPY, MOVE, and UID. 3432 6.4.1. CLOSE Command 3434 Arguments: none 3436 Responses: no specific responses for this command 3438 Result: OK - close completed, now in authenticated state 3439 BAD - command unknown or arguments invalid 3441 The CLOSE command permanently removes all messages that have the 3442 \Deleted flag set from the currently selected mailbox, and returns to 3443 the authenticated state from the selected state. No untagged EXPUNGE 3444 responses are sent. 3446 No messages are removed, and no error is given, if the mailbox is 3447 selected by an EXAMINE command or is otherwise selected read-only. 3449 Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT command 3450 MAY be issued without previously issuing a CLOSE command. The 3451 SELECT, EXAMINE, and LOGOUT commands implicitly close the currently 3452 selected mailbox without doing an expunge. However, when many 3453 messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT sequence is 3454 considerably faster than an EXPUNGE-LOGOUT or EXPUNGE-SELECT because 3455 no untagged EXPUNGE responses (which the client would probably 3456 ignore) are sent. 3458 Example: C: A341 CLOSE 3459 S: A341 OK CLOSE completed 3461 6.4.2. UNSELECT Command 3463 Arguments: none 3465 Responses: no specific responses for this command 3467 Result: OK - unselect completed, now in authenticated state 3468 BAD - no mailbox selected, or argument supplied but none 3469 permitted 3471 The UNSELECT command frees session's resources associated with the 3472 selected mailbox and returns the server to the authenticated state. 3473 This command performs the same actions as CLOSE, except that no 3474 messages are permanently removed from the currently selected mailbox. 3476 Example: C: A342 UNSELECT 3477 S: A342 OK Unselect completed 3479 6.4.3. EXPUNGE Command 3481 Arguments: none 3483 Responses: untagged responses: EXPUNGE 3485 Result: OK - expunge completed 3486 NO - expunge failure: can't expunge (e.g., permission 3487 denied) 3488 BAD - command unknown or arguments invalid 3490 The EXPUNGE command permanently removes all messages that have the 3491 \Deleted flag set from the currently selected mailbox. Before 3492 returning an OK to the client, an untagged EXPUNGE response is sent 3493 for each message that is removed. 3495 Example: C: A202 EXPUNGE 3496 S: * 3 EXPUNGE 3497 S: * 3 EXPUNGE 3498 S: * 5 EXPUNGE 3499 S: * 8 EXPUNGE 3500 S: A202 OK EXPUNGE completed 3502 Note: In this example, messages 3, 4, 7, and 11 had the \Deleted flag 3503 set. See the description of the EXPUNGE response (Section 7.5.1) for 3504 further explanation. 3506 6.4.4. SEARCH Command 3508 Arguments: OPTIONAL result specifier 3509 OPTIONAL [CHARSET] specification 3510 searching criteria (one or more) 3512 Responses: OPTIONAL untagged response: ESEARCH 3514 Result: OK - search completed 3515 NO - search error: can't search that [CHARSET] or 3516 criteria 3517 BAD - command unknown or arguments invalid 3519 The SEARCH command searches the mailbox for messages that match the 3520 given searching criteria. 3522 The SEARCH command may contain result options. Result options 3523 control what kind of information is returned about messages matching 3524 the search criteria in an untagged ESEARCH response. If no result 3525 option is specified or empty list of options is specified "()", ALL 3526 is assumed (see below). The order of individual options is 3527 arbitrary. Individual options may contain parameters enclosed in 3528 parentheses. (However, if an option has a mandatory parameter, which 3529 can always be represented as a number or a sequence-set, the option 3530 parameter does not need the enclosing parentheses. See the Formal 3531 Syntax (Section 9) for more details). If an option has parameters, 3532 they consist of atoms and/or strings and/or lists in a specific 3533 order. Any options not defined by extensions that the server 3534 supports MUST be rejected with a BAD response. 3536 This document specifies the following result options: 3538 MIN 3540 Return the lowest message number/UID that satisfies the SEARCH 3541 criteria. 3543 If the SEARCH results in no matches, the server MUST NOT 3544 include the MIN result option in the ESEARCH response; however, 3545 it still MUST send the ESEARCH response. 3547 MAX 3549 Return the highest message number/UID that satisfies the SEARCH 3550 criteria. 3552 If the SEARCH results in no matches, the server MUST NOT 3553 include the MAX result option in the ESEARCH response; however, 3554 it still MUST send the ESEARCH response. 3556 ALL 3558 Return all message numbers/UIDs that satisfy the SEARCH 3559 criteria using the sequence-set syntax. Note, the client MUST 3560 NOT assume that messages/UIDs will be listed in any particular 3561 order. 3563 If the SEARCH results in no matches, the server MUST NOT 3564 include the ALL result option in the ESEARCH response; however, 3565 it still MUST send the ESEARCH response. 3567 COUNT Return the number of messages that satisfy the SEARCH 3568 criteria. This result option MUST always be included in the 3569 ESEARCH response. 3571 SAVE 3573 This option tells the server to remember the result of the 3574 SEARCH or UID SEARCH command (as well as any command based on 3575 SEARCH, e.g., SORT and THREAD [RFC5256]>) and store it in an 3576 internal variable that we will reference as the "search result 3577 variable". The client can use the "$" marker to reference the 3578 content of this internal variable. The "$" marker can be used 3579 instead of message sequence or UID sequence in order to 3580 indicate that the server should substitute it with the list of 3581 messages from the search result variable. Thus, the client can 3582 use the result of the latest remembered SEARCH command as a 3583 parameter to another command. See Section 6.4.4.1 for details 3584 on how the value of the search result variable is determined, 3585 how it is affected by other commands executed, and how SAVE 3586 return option interacts with other return options. 3588 In absence of any other SEARCH result option, the SAVE result 3589 option also suppresses any ESEARCH response that would have 3590 been otherwise returned by the SEARCH command. 3592 Note: future extensions to this document can allow servers to return 3593 multiple ESEARCH responses for a single extended SEARCH command. 3594 However all options specified above MUST result in a single ESEARCH 3595 response if used by themselves or in combination. This guaranty 3596 simplifies processing in IMAP4rev2 clients. Future SEARCH extensions 3597 that relax this restriction will have to describe how results from 3598 multiple ESEARCH responses are to be combined. 3600 Searching criteria consist of one or more search keys. 3602 When multiple keys are specified, the result is the intersection (AND 3603 function) of all the messages that match those keys. For example, 3604 the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers to all 3605 deleted messages from Smith with INTERNALDATE greater than February 3606 1, 1994. A search key can also be a parenthesized list of one or 3607 more search keys (e.g., for use with the OR and NOT keys). 3609 Server implementations MAY exclude [MIME-IMB] body parts with 3610 terminal content media types other than TEXT and MESSAGE from 3611 consideration in SEARCH matching. 3613 The OPTIONAL [CHARSET] specification consists of the word "CHARSET" 3614 followed by a registered [CHARSET] [CHARSET-REG]. It indicates the 3615 [CHARSET] of the strings that appear in the search criteria. 3616 [MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in 3617 [RFC-5322]/[MIME-IMB] headers, MUST be decoded before comparing text. 3618 Servers MUST support US-ASCII and UTF-8 charsets; other [CHARSET]s 3619 MAY be supported. Clients SHOULD use UTF-8. Note that if "CHARSET" 3620 is not provided IMAP4rev2 server MUST assume UTF-8, so selecting 3621 CHARSET UTF-8 is redundant. It is permitted for improved 3622 compatibility with existing IMAP4rev1 clients. 3624 If the server does not support the specified [CHARSET], it MUST 3625 return a tagged NO response (not a BAD). This response SHOULD 3626 contain the BADCHARSET response code, which MAY list the [CHARSET]s 3627 supported by the server. 3629 In all search keys that use strings and unless specified otherwise, a 3630 message matches the key if the string is a substring of the 3631 associated text. The matching SHOULD be case-insensitive for 3632 characters within ASCII range. Consider using [IMAP-I18N] for 3633 language-sensitive case-insensitive searching. Note that the empty 3634 string is a substring; this is useful when doing a HEADER search in 3635 order to test for a header field presence in the message. 3637 The defined search keys are as follows. Refer to the Formal Syntax 3638 section for the precise syntactic definitions of the arguments. 3640 Messages with message sequence numbers corresponding 3641 to the specified message sequence number set. 3643 ALL All messages in the mailbox; the default initial key for ANDing. 3645 ANSWERED Messages with the \Answered flag set. 3647 BCC Messages that contain the specified string in the 3648 envelope structure's BCC field. 3650 BEFORE Messages whose internal date (disregarding time and 3651 timezone) is earlier than the specified date. 3653 BODY Messages that contain the specified string in the body 3654 of the message. Unlike TEXT (see below), this doesn't match any 3655 header fields. Servers are allowed to implement flexible matching 3656 for this search key, for example matching "swim" to both "swam" 3657 and "swum" in English language text or only doing full word 3658 matching (where "swim" will not match "swimming"). 3660 CC Messages that contain the specified string in the 3661 envelope structure's CC field. 3663 DELETED Messages with the \Deleted flag set. 3665 DRAFT Messages with the \Draft flag set. 3667 FLAGGED Messages with the \Flagged flag set. 3669 FROM Messages that contain the specified string in the 3670 envelope structure's FROM field. 3672 HEADER Messages that have a header field with 3673 the specified field-name (as defined in [RFC-5322]) and that 3674 contains the specified string in the text of the header field 3675 (what comes after the colon). If the string to search is zero- 3676 length, this matches all messages that have a header field with 3677 the specified field-name regardless of the contents. Servers 3678 should use substring search for this SEARCH item, as clients can 3679 use it for automatic processing not initiated by end users. For 3680 example this can be used for searching for Message-ID or Content- 3681 Type header field values that need to be exact, or for searches in 3682 header fields that the IMAP server might not know anything about. 3684 KEYWORD Messages with the specified keyword flag set. 3686 LARGER Messages with an [RFC-5322] size larger than the 3687 specified number of octets. 3689 NOT Messages that do not match the specified search 3690 key. 3692 ON Messages whose internal date (disregarding time and 3693 timezone) is within the specified date. 3695 OR Messages that match either search 3696 key. 3698 SEEN Messages that have the \Seen flag set. 3700 SENTBEFORE Messages whose [RFC-5322] Date: header field 3701 (disregarding time and timezone) is earlier than the specified 3702 date. 3704 SENTON Messages whose [RFC-5322] Date: header field 3705 (disregarding time and timezone) is within the specified date. 3707 SENTSINCE Messages whose [RFC-5322] Date: header field 3708 (disregarding time and timezone) is within or later than the 3709 specified date. 3711 SINCE Messages whose internal date (disregarding time and 3712 timezone) is within or later than the specified date. 3714 SMALLER Messages with an [RFC-5322] size smaller than the 3715 specified number of octets. 3717 SUBJECT Messages that contain the specified string in the 3718 envelope structure's SUBJECT field. 3720 TEXT Messages that contain the specified string in the 3721 header (including MIME header fields) or body of the message. 3722 Servers are allowed to implement flexible matching for this search 3723 key, for example matching "swim" to both "swam" and "swum" in 3724 English language text or only doing full word matching (where 3725 "swim" will not match "swimming"). 3727 TO Messages that contain the specified string in the 3728 envelope structure's TO field. 3730 UID Messages with unique identifiers corresponding to 3731 the specified unique identifier set. Sequence set ranges are 3732 permitted. 3734 UNANSWERED Messages that do not have the \Answered flag set. 3736 UNDELETED Messages that do not have the \Deleted flag set. 3738 UNDRAFT Messages that do not have the \Draft flag set. 3740 UNFLAGGED Messages that do not have the \Flagged flag set. 3742 UNKEYWORD Messages that do not have the specified keyword 3743 flag set. 3745 UNSEEN Messages that do not have the \Seen flag set. 3747 Example: C: A282 SEARCH RETURN (MIN COUNT) FLAGGED 3748 SINCE 1-Feb-1994 NOT FROM "Smith" 3749 S: * ESEARCH (TAG "A282") MIN 2 COUNT 3 3750 S: A282 OK SEARCH completed 3752 Example: C: A283 SEARCH RETURN () FLAGGED 3753 SINCE 1-Feb-1994 NOT FROM "Smith" 3754 S: * ESEARCH (TAG "A283") ALL 2,10:11 3755 S: A283 OK SEARCH completed 3757 Example: C: A284 SEARCH TEXT "string not in mailbox" 3758 S: * ESEARCH (TAG "A284") 3759 S: A284 OK SEARCH completed 3760 C: A285 SEARCH CHARSET UTF-8 TEXT {6} 3761 S: + Ready for literal text 3762 C: XXXXXX 3763 S: * ESEARCH (TAG "A285") ALL 43 3764 S: A285 OK SEARCH completed 3766 Note: Since this document is restricted to 7-bit ASCII text, it is 3767 not possible to show actual UTF-8 data. The "XXXXXX" is a 3768 placeholder for what would be 6 octets of 8-bit data in an actual 3769 transaction. 3771 The following example demonstrates finding the first unseen message 3772 in the mailbox: 3774 Example: C: A284 SEARCH RETURN (MIN) UNSEEN 3775 S: * ESEARCH (TAG "A284") MIN 4 3776 S: A284 OK SEARCH completed 3778 The following example demonstrates that if the ESEARCH UID indicator 3779 is present, all data in the ESEARCH response is referring to UIDs; 3780 for example, the MIN result specifier will be followed by a UID. 3782 Example: C: A285 UID SEARCH RETURN (MIN MAX) 1:5000 3783 S: * ESEARCH (TAG "A285") UID MIN 7 MAX 3800 3784 S: A285 OK SEARCH completed 3786 The following example demonstrates returning the number of deleted 3787 messages: 3789 Example: C: A286 SEARCH RETURN (COUNT) DELETED 3790 S: * ESEARCH (TAG "A286") COUNT 15 3791 S: A286 OK SEARCH completed 3793 6.4.4.1. SAVE result option and SEARCH result variable 3795 Upon successful completion of a SELECT or an EXAMINE command (after 3796 the tagged OK response), the current search result variable is reset 3797 to the empty sequence. 3799 A successful SEARCH command with the SAVE result option sets the 3800 value of the search result variable to the list of messages found in 3801 the SEARCH command. For example, if no messages were found, the 3802 search result variable will contain the empty sequence. 3804 Any of the following SEARCH commands MUST NOT change the search 3805 result variable: 3807 a SEARCH command that caused the server to return the BAD tagged 3808 response, 3810 a SEARCH command with no SAVE result option that caused the server 3811 to return NO tagged response, 3813 a successful SEARCH command with no SAVE result option. 3815 A SEARCH command with the SAVE result option that caused the server 3816 to return the NO tagged response sets the value of the search result 3817 variable to the empty sequence. 3819 When a message listed in the search result variable is EXPUNGEd, it 3820 is automatically removed from the list. Implementors are reminded 3821 that if the server stores the list as a list of message numbers, it 3822 MUST automatically adjust them when notifying the client about 3823 expunged messages, as described in Section 7.5.1. 3825 If the server decides to send a new UIDVALIDITY value while the 3826 mailbox is opened, this causes resetting of the search variable to 3827 the empty sequence. 3829 Note that even if the "$" marker contains the empty sequence of 3830 messages, it must be treated by all commands accepting message sets 3831 as parameters as a valid, but non-matching list of messages. For 3832 example, the "FETCH $" command would return a tagged OK response and 3833 no FETCH responses. See also the Example 5 in Section 6.4.4.4. 3835 The SAVE result option doesn't change whether the server would return 3836 items corresponding to MIN, MAX, ALL, or COUNT result options. 3838 When the SAVE result option is combined with the MIN or MAX result 3839 option, and both ALL and COUNT result options are absent, the 3840 corresponding MIN/MAX is returned (if the search result is not 3841 empty), but the "$" marker would contain a single message as returned 3842 in the MIN/MAX return item. 3844 If the SAVE result option is combined with both MIN and MAX result 3845 options, and both ALL and COUNT result options are absent, the "$" 3846 marker would contain zero, one or two messages as returned in the 3847 MIN/MAX return items. 3849 If the SAVE result option is combined with the ALL and/or COUNT 3850 result option(s), the "$" marker would always contain all messages 3851 found by the SEARCH or UID SEARCH command. 3853 The following table summarizes the additional requirement on ESEARCH 3854 server implementations described in this section. 3856 +------------------------------+--------------------+ 3857 | Combination of Result option | "$" marker value | 3858 +------------------------------+--------------------+ 3859 | SAVE MIN | MIN | 3860 | SAVE MAX | MAX | 3861 | SAVE MIN MAX | MIN & MAX | 3862 | SAVE * [m] | all found messages | 3863 +------------------------------+--------------------+ 3865 where '*' means "ALL" and/or "COUNT", and '[m]' means optional "MIN" 3866 and/or "MAX" 3868 Implementation note: server implementors should note that "$" can 3869 reference IMAP message sequences or UID sequences, depending on the 3870 context where it is used. For example, the "$" marker can be set as 3871 a result of a SEARCH (SAVE) command and used as a parameter to a UID 3872 FETCH command (which accepts a UID sequence, not a message sequence), 3873 or the "$" marker can be set as a result of a UID SEARCH (SAVE) 3874 command and used as a parameter to a FETCH command (which accepts a 3875 message sequence, not a UID sequence). Server implementations need 3876 to automatically map the "$" marker value to message numbers or UIDs, 3877 depending on context where the "$" marker is used. 3879 6.4.4.2. Multiple Commands in Progress 3881 Use of a SEARCH RETURN (SAVE) command followed by a command using the 3882 "$" marker creates direct dependency between the two commands. As 3883 directed by Section 5.5, a server MUST execute the two commands in 3884 the order they were received. 3886 A client MAY pipeline a SEARCH RETURN (SAVE) command with one or more 3887 command using the "$" marker, as long as this doesn't create an 3888 ambiguity, as described in Section 5.5. Examples 7-9 in 3889 Section 6.4.4.4 explain this in more details. 3891 6.4.4.3. Refusing to Save Search Results 3893 In some cases, the server MAY refuse to save a SEARCH (SAVE) result, 3894 for example, if an internal limit on the number of saved results is 3895 reached. In this case, the server MUST return a tagged NO response 3896 containing the NOTSAVED response code and set the search result 3897 variable to the empty sequence, as described in Section 6.4.4.1. 3899 6.4.4.4. Examples showing use of SAVE result option 3901 Only in this section: explanatory comments in examples that start 3902 with // are not part of the protocol. 3904 1) The following example demonstrates how the client can use the 3905 result of a SEARCH command to FETCH headers of interesting messages: 3907 Example 1: 3908 C: A282 SEARCH RETURN (SAVE) FLAGGED SINCE 1-Feb-1994 3909 NOT FROM "Smith" 3910 S: A282 OK SEARCH completed, result saved 3911 C: A283 FETCH $ (UID INTERNALDATE FLAGS BODY.PEEK[HEADER]) 3912 S: * 2 FETCH (UID 14 ... 3913 S: * 84 FETCH (UID 100 ... 3914 S: * 882 FETCH (UID 1115 ... 3915 S: A283 OK completed 3917 The client can also pipeline the two commands: 3919 Example 2: 3920 C: A282 SEARCH RETURN (SAVE) FLAGGED SINCE 1-Feb-1994 3921 NOT FROM "Smith" 3922 C: A283 FETCH $ (UID INTERNALDATE FLAGS BODY.PEEK[HEADER]) 3923 S: A282 OK SEARCH completed 3924 S: * 2 FETCH (UID 14 ... 3925 S: * 84 FETCH (UID 100 ... 3926 S: * 882 FETCH (UID 1115 ... 3927 S: A283 OK completed 3929 2) The following example demonstrates that the result of one SEARCH 3930 command can be used as input to another SEARCH command: 3932 Example 3: 3933 C: A300 SEARCH RETURN (SAVE) SINCE 1-Jan-2004 3934 NOT FROM "Smith" 3935 S: A300 OK SEARCH completed 3936 C: A301 UID SEARCH UID $ SMALLER 4096 3937 S: * ESEARCH (TAG "A301") UID ALL 17,900,901 3938 S: A301 OK completed 3940 Note that the second command in Example 3 can be replaced with: 3941 C: A301 UID SEARCH $ SMALLER 4096 3942 and the result of the command would be the same. 3944 3) The following example shows that the "$" marker can be combined 3945 with other message numbers using the OR SEARCH criterion. 3947 Example 4: 3948 C: P282 SEARCH RETURN (SAVE) SINCE 1-Feb-1994 3949 NOT FROM "Smith" 3950 S: P282 OK SEARCH completed 3951 C: P283 SEARCH CHARSET UTF-8 (OR $ 1,3000:3021) TEXT {8} 3952 C: YYYYYYYY 3953 S: * ESEARCH (TAG "P283") ALL 882,1102,3003,3005:3006 3954 S: P283 OK completed 3956 Note: Since this document format is restricted to 7-bit ASCII text, 3957 it is not possible to show actual UTF-8 data. The "YYYYYYYY" is a 3958 placeholder for what would be 8 octets of 8-bit data in an actual 3959 transaction. 3961 4) The following example demonstrates that a failed SEARCH sets the 3962 search result variable to the empty list. The server doesn't 3963 implement the KOI8-R charset. 3965 Example 5: 3966 C: B282 SEARCH RETURN (SAVE) SINCE 1-Feb-1994 3967 NOT FROM "Smith" 3968 S: B282 OK SEARCH completed 3969 C: B283 SEARCH RETURN (SAVE) CHARSET KOI8-R 3970 (OR $ 1,3000:3021) TEXT {4} 3971 C: XXXX 3972 S: B283 NO [BADCHARSET UTF-8] KOI8-R is not supported 3973 //After this command the saved result variable contains 3974 //no messages. A client that wants to reissue the B283 3975 //SEARCH command with another CHARSET would have to reissue 3976 //the B282 command as well. One possible workaround for 3977 //this is to include the desired CHARSET parameter 3978 //in the earliest SEARCH RETURN (SAVE) command in a 3979 //sequence of related SEARCH commands, to cause 3980 //the earliest SEARCH in the sequence to fail. 3981 //A better approach might be to always use CHARSET UTF-8 3982 //instead. 3984 Note: Since this document format is restricted to 7-bit ASCII text, 3985 it is not possible to show actual KOI8-R data. The "XXXX" is a 3986 placeholder for what would be 4 octets of 8-bit data in an actual 3987 transaction. 3989 5) The following example demonstrates that it is not an error to use 3990 the "$" marker when it contains no messages. 3992 Example 6: 3993 C: E282 SEARCH RETURN (SAVE) SINCE 28-Oct-2006 3994 NOT FROM "Eric" 3995 C: E283 COPY $ "Other Messages" 3996 //The "$" contains no messages 3997 S: E282 OK SEARCH completed 3998 S: E283 OK COPY completed, nothing copied 4000 Example 7: 4001 C: F282 SEARCH RETURN (SAVE) KEYWORD $Junk 4002 C: F283 COPY $ "Junk" 4003 C: F284 STORE $ +FLAGS.Silent (\Deleted) 4004 S: F282 OK SEARCH completed 4005 S: F283 OK COPY completed 4006 S: F284 OK STORE completed 4008 Example 8: 4009 C: G282 SEARCH RETURN (SAVE) KEYWORD $Junk 4010 C: G283 SEARCH RETURN (ALL) SINCE 28-Oct-2006 4011 FROM "Eric" 4012 // The server can execute the two SEARCH commands 4013 // in any order, as they don't have any dependency. 4014 // For example, it may return: 4015 S: * ESEARCH (TAG "G283") ALL 3:15,27,29:103 4016 S: G283 OK SEARCH completed 4017 S: G282 OK SEARCH completed 4019 The following example demonstrates that the result of the second 4020 SEARCH RETURN (SAVE) always overrides the result of the first. 4022 Example 9: 4023 C: H282 SEARCH RETURN (SAVE) KEYWORD $Junk 4024 C: H283 SEARCH RETURN (SAVE) SINCE 28-Oct-2006 4025 FROM "Eric" 4026 S: H282 OK SEARCH completed 4027 S: H283 OK SEARCH completed 4028 // At this point "$" would contain results of H283 4030 The following example demonstrates behavioral difference for 4031 different combinations of ESEARCH result options. 4033 Example 10: 4034 C: C282 SEARCH RETURN (ALL) SINCE 12-Feb-2006 4035 NOT FROM "Smith" 4036 S: * ESEARCH (TAG "C283") ALL 2,10:15,21 4037 //$ value hasn't changed 4038 S: C282 OK SEARCH completed 4040 C: C283 SEARCH RETURN (ALL SAVE) SINCE 12-Feb-2006 4041 NOT FROM "Smith" 4042 S: * ESEARCH (TAG "C283") ALL 2,10:15,21 4043 //$ value is 2,10:15,21 4044 S: C283 OK SEARCH completed 4046 C: C284 SEARCH RETURN (SAVE MIN) SINCE 12-Feb-2006 4047 NOT FROM "Smith" 4048 S: * ESEARCH (TAG "C284") MIN 2 4049 //$ value is 2 4050 S: C284 OK SEARCH completed 4052 C: C285 SEARCH RETURN (MAX SAVE MIN) SINCE 4053 12-Feb-2006 NOT FROM "Smith" 4054 S: * ESEARCH (TAG "C285") MIN 2 MAX 21 4055 //$ value is 2,21 4056 S: C285 OK SEARCH completed 4058 C: C286 SEARCH RETURN (MAX SAVE MIN COUNT) 4059 SINCE 12-Feb-2006 NOT FROM "Smith" 4060 S: * ESEARCH (TAG "C286") MIN 2 MAX 21 COUNT 8 4061 //$ value is 2,10:15,21 4062 S: C286 OK SEARCH completed 4064 C: C286 SEARCH RETURN (ALL SAVE MIN) SINCE 4065 12-Feb-2006 NOT FROM "Smith" 4066 S: * ESEARCH (TAG "C286") MIN 2 ALL 2,10:15,21 4067 //$ value is 2,10:15,21 4068 S: C286 OK SEARCH completed 4070 6.4.5. FETCH Command 4072 Arguments: sequence set 4073 message data item names or macro 4075 Responses: untagged responses: FETCH 4077 Result: OK - fetch completed 4078 NO - fetch error: can't fetch that data 4079 BAD - command unknown or arguments invalid 4081 The FETCH command retrieves data associated with a message in the 4082 mailbox. The data items to be fetched can be either a single atom or 4083 a parenthesized list. 4085 Most data items, identified in the formal syntax (Section 9) under 4086 the msg-att-static rule, are static and MUST NOT change for any 4087 particular message. Other data items, identified in the formal 4088 syntax under the msg-att-dynamic rule, MAY change, either as a result 4089 of a STORE command or due to external events. 4091 For example, if a client receives an ENVELOPE for a message when 4092 it already knows the envelope, it can safely ignore the newly 4093 transmitted envelope. 4095 There are three macros which specify commonly-used sets of data 4096 items, and can be used instead of data items. A macro must be used 4097 by itself, and not in conjunction with other macros or data items. 4099 ALL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE) 4101 FAST Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE) 4103 FULL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE 4104 BODY) 4106 Several data items reference "section" or "section-binary". See 4107 Section 6.4.5.1 for their detailed definition. 4109 The currently defined data items that can be fetched are: 4111 BINARY[]<> 4113 Requests that the specified section be transmitted after 4114 performing Content-Transfer-Encoding-related decoding. 4116 The argument, if present, requests that a subset of 4117 the data be returned. The semantics of a partial FETCH BINARY 4118 command are the same as for a partial FETCH BODY command, with 4119 the exception that the arguments refer to the DECODED 4120 section data. 4122 Note that this data item can only be requested for leaf (i.e. 4123 non multipart/*, non message/rfc822 and non message/global) 4124 body parts. 4126 BINARY.PEEK[]<> An alternate form of 4127 BINARY[] that does not implicitly set the \Seen 4128 flag. 4130 BINARY.SIZE[] 4132 Requests the decoded size of the section (i.e., the size to 4133 expect in response to the corresponding FETCH BINARY request). 4135 Note: client authors are cautioned that this might be an 4136 expensive operation for some server implementations. 4137 Needlessly issuing this request could result in degraded 4138 performance due to servers having to calculate the value every 4139 time the request is issued. 4141 Note that this data item can only be requested for leaf (i.e. 4142 non multipart/*, non message/rfc822 and non message/global) 4143 body parts. 4145 BODY Non-extensible form of BODYSTRUCTURE. 4147 BODY[
]<> 4149 The text of a particular body section. 4151 It is possible to fetch a substring of the designated text. 4152 This is done by appending an open angle bracket ("<"), the 4153 octet position of the first desired octet, a period, the 4154 maximum number of octets desired, and a close angle bracket 4155 (">") to the part specifier. If the starting octet is beyond 4156 the end of the text, an empty string is returned. 4158 Any partial fetch that attempts to read beyond the end of the 4159 text is truncated as appropriate. A partial fetch that starts 4160 at octet 0 is returned as a partial fetch, even if this 4161 truncation happened. 4163 Note: This means that BODY[]<0.2048> of a 1500-octet message 4164 will return BODY[]<0> with a literal of size 1500, not 4165 BODY[]. 4167 Note: A substring fetch of a HEADER.FIELDS or 4168 HEADER.FIELDS.NOT part specifier is calculated after 4169 subsetting the header. 4171 The \Seen flag is implicitly set; if this causes the flags to 4172 change, they SHOULD be included as part of the FETCH responses. 4174 BODY.PEEK[
]<> An alternate form of BODY[
] 4175 that does not implicitly set the \Seen flag. 4177 BODYSTRUCTURE The [MIME-IMB] body structure of the message. This is 4178 computed by the server by parsing the [MIME-IMB] header fields in 4179 the [RFC-5322] header and [MIME-IMB] headers. See Section 7.5.2 4180 for more details. 4182 ENVELOPE The envelope structure of the message. This is computed by 4183 the server by parsing the [RFC-5322] header into the component 4184 parts, defaulting various fields as necessary. See Section 7.5.2 4185 for more details. 4187 FLAGS The flags that are set for this message. 4189 INTERNALDATE The internal date of the message. 4191 RFC822.SIZE The [RFC-5322] size of the message. 4193 UID The unique identifier for the message. 4195 Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)]) 4196 S: * 2 FETCH .... 4197 S: * 3 FETCH .... 4198 S: * 4 FETCH .... 4199 S: A654 OK FETCH completed 4201 6.4.5.1. FETCH section specification 4203 Several FETCH data items reference "section" or "section-binary". 4204 The section specification is a set of zero or more part specifiers 4205 delimited by periods. A part specifier is either a part number or 4206 one of the following: HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, MIME, 4207 and TEXT. (Non numeric part specifiers have to be the last specifier 4208 in a section specification.) An empty section specification refers 4209 to the entire message, including the header. 4211 Every message has at least one part number. Non-[MIME-IMB] messages, 4212 and non-multipart [MIME-IMB] messages with no encapsulated message, 4213 only have a part 1. 4215 Multipart messages are assigned consecutive part numbers, as they 4216 occur in the message. If a particular part is of type message or 4217 multipart, its parts MUST be indicated by a period followed by the 4218 part number within that nested multipart part. 4220 A part of type MESSAGE/RFC822 or MESSAGE/GLOBAL also has nested part 4221 numbers, referring to parts of the MESSAGE part's body. 4223 The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part 4224 specifiers can be the sole part specifier or can be prefixed by one 4225 or more numeric part specifiers, provided that the numeric part 4226 specifier refers to a part of type MESSAGE/RFC822 or MESSAGE/GLOBAL. 4227 The MIME part specifier MUST be prefixed by one or more numeric part 4228 specifiers. 4230 The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part specifiers 4231 refer to the [RFC-5322] header of the message or of an encapsulated 4232 [MIME-IMT] MESSAGE/RFC822 or MESSAGE/GLOBAL message. HEADER.FIELDS 4233 and HEADER.FIELDS.NOT are followed by a list of field-name (as 4234 defined in [RFC-5322]) names, and return a subset of the header. The 4235 subset returned by HEADER.FIELDS contains only those header fields 4236 with a field-name that matches one of the names in the list; 4237 similarly, the subset returned by HEADER.FIELDS.NOT contains only the 4238 header fields with a non-matching field-name. The field-matching is 4239 ASCII range case-insensitive but otherwise exact. Subsetting does 4240 not exclude the [RFC-5322] delimiting blank line between the header 4241 and the body; the blank line is included in all header fetches, 4242 except in the case of a message which has no body and no blank line. 4244 The MIME part specifier refers to the [MIME-IMB] header for this 4245 part. 4247 The TEXT part specifier refers to the text body of the message, 4248 omitting the [RFC-5322] header. 4250 Here is an example of a complex message with some of its part 4251 specifiers: 4253 HEADER ([RFC-5322] header of the message) 4254 TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 4255 1 TEXT/PLAIN 4256 2 APPLICATION/OCTET-STREAM 4257 3 MESSAGE/RFC822 4258 3.HEADER ([RFC-5322] header of the message) 4259 3.TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 4260 3.1 TEXT/PLAIN 4261 3.2 APPLICATION/OCTET-STREAM 4262 4 MULTIPART/MIXED 4263 4.1 IMAGE/GIF 4264 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF) 4265 4.2 MESSAGE/RFC822 4266 4.2.HEADER ([RFC-5322] header of the message) 4267 4.2.TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 4268 4.2.1 TEXT/PLAIN 4269 4.2.2 MULTIPART/ALTERNATIVE 4270 4.2.2.1 TEXT/PLAIN 4271 4.2.2.2 TEXT/RICHTEXT 4273 6.4.6. STORE Command 4275 Arguments: sequence set 4276 message data item name 4277 value for message data item 4279 Responses: untagged responses: FETCH 4281 Result: OK - store completed 4282 NO - store error: can't store that data 4283 BAD - command unknown or arguments invalid 4285 The STORE command alters data associated with a message in the 4286 mailbox. Normally, STORE will return the updated value of the data 4287 with an untagged FETCH response. A suffix of ".SILENT" in the data 4288 item name prevents the untagged FETCH, and the server SHOULD assume 4289 that the client has determined the updated value itself or does not 4290 care about the updated value. 4292 Note: Regardless of whether or not the ".SILENT" suffix was used, 4293 the server SHOULD send an untagged FETCH response if a change to a 4294 message's flags from an external source is observed. The intent 4295 is that the status of the flags is determinate without a race 4296 condition. 4298 The currently defined data items that can be stored are: 4300 FLAGS Replace the flags for the message with the 4301 argument. The new value of the flags is returned as if a FETCH of 4302 those flags was done. 4304 FLAGS.SILENT Equivalent to FLAGS, but without returning 4305 a new value. 4307 +FLAGS Add the argument to the flags for the message. 4308 The new value of the flags is returned as if a FETCH of those 4309 flags was done. 4311 +FLAGS.SILENT Equivalent to +FLAGS, but without 4312 returning a new value. 4314 -FLAGS Remove the argument from the flags for the 4315 message. The new value of the flags is returned as if a FETCH of 4316 those flags was done. 4318 -FLAGS.SILENT Equivalent to -FLAGS, but without 4319 returning a new value. 4321 Example: C: A003 STORE 2:4 +FLAGS (\Deleted) 4322 S: * 2 FETCH (FLAGS (\Deleted \Seen)) 4323 S: * 3 FETCH (FLAGS (\Deleted)) 4324 S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen)) 4325 S: A003 OK STORE completed 4327 6.4.7. COPY Command 4329 Arguments: sequence set 4330 mailbox name 4332 Responses: no specific responses for this command 4334 Result: OK - copy completed 4335 NO - copy error: can't copy those messages or to that 4336 name 4337 BAD - command unknown or arguments invalid 4339 The COPY command copies the specified message(s) to the end of the 4340 specified destination mailbox. The flags and internal date of the 4341 message(s) SHOULD be preserved in the copy. 4343 If the destination mailbox does not exist, a server MUST return an 4344 error. It MUST NOT automatically create the mailbox. Unless it is 4345 certain that the destination mailbox can not be created, the server 4346 MUST send the response code "[TRYCREATE]" as the prefix of the text 4347 of the tagged NO response. This gives a hint to the client that it 4348 can attempt a CREATE command and retry the COPY if the CREATE is 4349 successful. 4351 If the COPY command is unsuccessful for any reason, server 4352 implementations MUST restore the destination mailbox to its state 4353 before the COPY attempt (other than possibly incrementing UIDNEXT), 4354 i.e. partial copy MUST NOT be done. 4356 On successful completion of a COPY, the server returns a COPYUID 4357 response code (see Section 7.1). Two exception to this requirement 4358 are listed below. 4360 In the case of a mailbox that has permissions set so that the client 4361 can COPY to the mailbox, but not SELECT or EXAMINE it, the server 4362 MUST NOT send an COPYUID response code as it would disclose 4363 information about the mailbox. 4365 In the case of a mailbox that has UIDNOTSTICKY status (see 4366 Section 7.1), the server MAY omit the COPYUID response code as it is 4367 not meaningful. 4369 Example: C: A003 COPY 2:4 MEETING 4370 S: A003 OK [COPYUID 38505 304,319:320 3956:3958] COPY completed 4372 6.4.8. MOVE Command 4374 Arguments: sequence set 4375 mailbox name 4377 Responses: no specific responses for this command 4379 Result: OK - move completed 4380 NO - move error: can't move those messages or to that 4381 name 4382 BAD - command unknown or arguments invalid 4384 The MOVE command moves the specified message(s) to the end of the 4385 specified destination mailbox. The flags and internal date of the 4386 message(s) SHOULD be preserved. 4388 This means that a new message is created in the target mailbox with a 4389 new UID, the original message is removed from the source mailbox, and 4390 it appears to the client as a single action. This has the same 4391 effect for each message as this sequence: 4393 1. [UID] COPY 4395 2. [UID] STORE +FLAGS.SILENT \DELETED 4397 3. UID EXPUNGE 4399 Although the effect of the MOVE is the same as the preceding steps, 4400 the semantics are not identical: The intermediate states produced by 4401 those steps do not occur, and the response codes are different. In 4402 particular, though the COPY and EXPUNGE response codes will be 4403 returned, response codes for a STORE MUST NOT be generated and the 4404 \Deleted flag MUST NOT be set for any message. 4406 Unlike the COPY command, MOVE of a set of messages might fail partway 4407 through the set. Regardless of whether the command is successful in 4408 moving the entire set, each individual message MUST either be moved 4409 or unaffected. The server MUST leave each message in a state where 4410 it is in at least one of the source or target mailboxes (no message 4411 can be lost or orphaned). The server SHOULD NOT leave any message in 4412 both mailboxes (it would be bad for a partial failure to result in a 4413 bunch of duplicate messages). This is true even if the server 4414 returns a tagged NO response to the command. 4416 If the destination mailbox does not exist, a server MUST return an 4417 error. It MUST NOT automatically create the mailbox. Unless it is 4418 certain that the destination mailbox can not be created, the server 4419 MUST send the response code "[TRYCREATE]" as the prefix of the text 4420 of the tagged NO response. This gives a hint to the client that it 4421 can attempt a CREATE command and retry the MOVE if the CREATE is 4422 successful. 4424 Because of the similarity of MOVE to COPY, extensions that affect 4425 COPY affect MOVE in the same way. Response codes listed in 4426 Section 7.1, as well as those defined by extensions, are sent as 4427 appropriate. 4429 Servers send COPYUID in response to a MOVE or a UID MOVE (see 4430 Section 6.4.9) command. For additional information about COPYUID see 4431 Section 7.1. Note that there are several exceptions listed in 4432 Section 6.4.7 that allow servers not to return COPYUID. 4434 Servers are also REQUIRED to send the COPYUID response code in an 4435 untagged OK before sending EXPUNGE or similar responses. (Sending 4436 COPYUID in the tagged OK, as described in the UIDPLUS specification, 4437 means that clients first receive an EXPUNGE for a message and 4438 afterwards COPYUID for the same message. It can be unnecessarily 4439 difficult to process that sequence usefully.) 4441 An example: 4442 C: a UID MOVE 42:69 foo 4443 S: * OK [COPYUID 432432 42:69 1202:1229] 4444 S: * 22 EXPUNGE 4445 ...More EXPUNGE responses from the server... 4446 S: a OK Done 4448 Note that the server may send unrelated EXPUNGE responses as well, if 4449 any happen to have been expunged at the same time; this is normal 4450 IMAP operation. 4452 Note that moving a message to the currently selected mailbox (that 4453 is, where the source and target mailboxes are the same) is allowed 4454 when copying the message to the currently selected mailbox is 4455 allowed. 4457 The server may send EXPUNGE responses before the tagged response, so 4458 the client cannot safely send more commands with message sequence 4459 number arguments while the server is processing MOVE. 4461 MOVE and UID MOVE can be pipelined with other commands, but care has 4462 to be taken. Both commands modify sequence numbers and also allow 4463 unrelated EXPUNGE responses. The renumbering of other messages in 4464 the source mailbox following any EXPUNGE response can be surprising 4465 and makes it unsafe to pipeline any command that relies on message 4466 sequence numbers after a MOVE or UID MOVE. Similarly, MOVE cannot be 4467 pipelined with a command that might cause message renumbering. See 4468 Section 5.5, for more information about ambiguities as well as 4469 handling requirements for both clients and servers. 4471 6.4.9. UID Command 4473 Arguments: command name 4474 command arguments 4476 Responses: untagged responses: FETCH, ESEARCH, EXPUNGE 4478 Result: OK - UID command completed 4479 NO - UID command error 4480 BAD - command unknown or arguments invalid 4482 The UID command has three forms. In the first form, it takes as its 4483 arguments a COPY, MOVE, FETCH, or STORE command with arguments 4484 appropriate for the associated command. However, the numbers in the 4485 sequence set argument are unique identifiers instead of message 4486 sequence numbers. Sequence set ranges are permitted, but there is no 4487 guarantee that unique identifiers will be contiguous. 4489 A non-existent unique identifier is ignored without any error message 4490 generated. Thus, it is possible for a UID FETCH command to return an 4491 OK without any data or a UID COPY, UID MOVE or UID STORE to return an 4492 OK without performing any operations. 4494 In the second form, the UID command takes an EXPUNGE command with an 4495 extra parameter the specified a sequence set of UIDs to operate on. 4496 The UID EXPUNGE command permanently removes all messages that both 4497 have the \Deleted flag set and have a UID that is included in the 4498 specified sequence set from the currently selected mailbox. If a 4499 message either does not have the \Deleted flag set or has a UID that 4500 is not included in the specified sequence set, it is not affected. 4502 UID EXPUNGE is particularly useful for disconnected use clients. 4503 By using UID EXPUNGE instead of EXPUNGE when resynchronizing with 4504 the server, the client can ensure that it does not inadvertantly 4505 remove any messages that have been marked as \Deleted by other 4506 clients between the time that the client was last connected and 4507 the time the client resynchronizes. 4509 Example: C: A003 UID EXPUNGE 3000:3002 4510 S: * 3 EXPUNGE 4511 S: * 3 EXPUNGE 4512 S: * 3 EXPUNGE 4513 S: A003 OK UID EXPUNGE completed 4515 In the third form, the UID command takes a SEARCH command with SEARCH 4516 command arguments. The interpretation of the arguments is the same 4517 as with SEARCH; however, the numbers returned in a ESEARCH response 4518 for a UID SEARCH command are unique identifiers instead of message 4519 sequence numbers. Also, the corresponding ESEARCH response MUST 4520 include the UID indicator. For example, the command UID SEARCH 1:100 4521 UID 443:557 returns the unique identifiers corresponding to the 4522 intersection of two sequence sets, the message sequence number range 4523 1:100 and the UID range 443:557. 4525 Note: in the above example, the UID range 443:557 appears. The 4526 same comment about a non-existent unique identifier being ignored 4527 without any error message also applies here. Hence, even if 4528 neither UID 443 or 557 exist, this range is valid and would 4529 include an existing UID 495. 4531 Also note that a UID range of 559:* always includes the UID of the 4532 last message in the mailbox, even if 559 is higher than any 4533 assigned UID value. This is because the contents of a range are 4534 independent of the order of the range endpoints. Thus, any UID 4535 range with * as one of the endpoints indicates at least one 4536 message (the message with the highest numbered UID), unless the 4537 mailbox is empty. 4539 The number after the "*" in an untagged FETCH or EXPUNGE response is 4540 always a message sequence number, not a unique identifier, even for a 4541 UID command response. However, server implementations MUST 4542 implicitly include the UID message data item as part of any FETCH 4543 response caused by a UID command, regardless of whether a UID was 4544 specified as a message data item to the FETCH. 4546 Note: The rule about including the UID message data item as part of a 4547 FETCH response primarily applies to the UID FETCH and UID STORE 4548 commands, including a UID FETCH command that does not include UID as 4549 a message data item. Although it is unlikely that the other UID 4550 commands will cause an untagged FETCH, this rule applies to these 4551 commands as well. 4553 Example: C: A999 UID FETCH 4827313:4828442 FLAGS 4554 S: * 23 FETCH (FLAGS (\Seen) UID 4827313) 4555 S: * 24 FETCH (FLAGS (\Seen) UID 4827943) 4556 S: * 25 FETCH (FLAGS (\Seen) UID 4828442) 4557 S: A999 OK UID FETCH completed 4559 6.5. Client Commands - Experimental/Expansion 4561 Each command which is not part of this specification MUST have at 4562 least one capability name (see Section 6.1.1) associated with it. 4563 (Multiple commands can be associated with the same capability name) 4565 Server implementations MUST NOT send any added (not specified in this 4566 specification) untagged responses, unless the client requested it by 4567 issuing the associated experimental command or the ENABLE command 4568 (Section 6.3.1). 4570 The following example demonstrates how a client can check for 4571 presence of a fictitious XPIG-LATIN capability that adds the XPIG- 4572 LATIN command and the the XPIG-LATIN untagged response. (Note that 4573 for an extension the command name and the capability name don't have 4574 to be the same.) 4576 Example: C: a441 CAPABILITY 4577 S: * CAPABILITY IMAP4rev2 XPIG-LATIN 4578 S: a441 OK CAPABILITY completed 4579 C: A442 XPIG-LATIN 4580 S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay 4581 S: A442 OK XPIG-LATIN ompleted-cay 4583 7. Server Responses 4585 Server responses are in three forms: status responses, server data, 4586 and command continuation request. The information contained in a 4587 server response, identified by "Contents:" in the response 4588 descriptions below, is described by function, not by syntax. The 4589 precise syntax of server responses is described in the Formal Syntax 4590 (Section 9). 4592 The client MUST be prepared to accept any response at all times. 4594 Status responses can be tagged or untagged. Tagged status responses 4595 indicate the completion result (OK, NO, or BAD status) of a client 4596 command, and have a tag matching the command. 4598 Some status responses, and all server data, are untagged. An 4599 untagged response is indicated by the token "*" instead of a tag. 4600 Untagged status responses indicate server greeting, or server status 4601 that does not indicate the completion of a command (for example, an 4602 impending system shutdown alert). For historical reasons, untagged 4603 server data responses are also called "unsolicited data", although 4604 strictly speaking, only unilateral server data is truly 4605 "unsolicited". 4607 Certain server data MUST be remembered by the client when it is 4608 received; this is noted in the description of that data. Such data 4609 conveys critical information which affects the interpretation of all 4610 subsequent commands and responses (e.g., updates reflecting the 4611 creation or destruction of messages). 4613 Other server data SHOULD be remembered for later reference; if the 4614 client does not need to remember the data, or if remembering the data 4615 has no obvious purpose (e.g., a SEARCH response when no SEARCH 4616 command is in progress), the data can be ignored. 4618 An example of unilateral untagged server data occurs when the IMAP 4619 connection is in the selected state. In the selected state, the 4620 server checks the mailbox for new messages as part of command 4621 execution. Normally, this is part of the execution of every command; 4622 hence, a NOOP command suffices to check for new messages. If new 4623 messages are found, the server sends untagged EXISTS response 4624 reflecting the new size of the mailbox. Server implementations that 4625 offer multiple simultaneous access to the same mailbox SHOULD also 4626 send appropriate unilateral untagged FETCH and EXPUNGE responses if 4627 another agent changes the state of any message flags or expunges any 4628 messages. 4630 Command continuation request responses use the token "+" instead of a 4631 tag. These responses are sent by the server to indicate acceptance 4632 of an incomplete client command and readiness for the remainder of 4633 the command. 4635 7.1. Server Responses - Generic Status Responses 4637 Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD 4638 can be tagged or untagged. PREAUTH and BYE are always untagged. 4640 Status responses MAY include an OPTIONAL "response code". A response 4641 code consists of data inside square brackets in the form of an atom, 4642 possibly followed by a space and arguments. The response code 4643 contains additional information or status codes for client software 4644 beyond the OK/NO/BAD condition, and are defined when there is a 4645 specific action that a client can take based upon the additional 4646 information. 4648 The currently defined response codes are: 4650 ALERT 4652 The human-readable text contains a special alert that are 4653 presented to the user in a fashion that calls the user's 4654 attention to the message. Content of ALERT response codes 4655 received on a connection without TLS or SASL security layer 4656 confidentiality SHOULD be ignored by clients. If displayed, 4657 such alerts MUST be clearly marked as potentially suspicious. 4658 (Note that some existing clients are known to hyperlink 4659 returned text which make them very dangerous.) Alerts received 4660 after successful establishment of a TLS/SASL confidentiality 4661 layer MUST be presented to the user. 4663 ALREADYEXISTS 4665 The operation attempts to create something that already exists, 4666 such as when the CREATE or RENAME directories attempt to create 4667 a mailbox and there is already one of that name. 4669 C: o356 RENAME this that 4670 S: o356 NO [ALREADYEXISTS] Mailbox "that" already exists 4672 APPENDUID 4674 Followed by the UIDVALIDITY of the destination mailbox and the 4675 UID assigned to the appended message in the destination 4676 mailbox, indicates that the message has been appended to the 4677 destination mailbox with that UID. 4679 If the server also supports the [MULTIAPPEND] extension, and if 4680 multiple messages were appended in the APPEND command, then the 4681 second value is a UID set containing the UIDs assigned to the 4682 appended messages, in the order they were transmitted in the 4683 APPEND command. This UID set may not contain extraneous UIDs 4684 or the symbol "*". 4686 Note: the UID set form of the APPENDUID response code MUST 4687 NOT be used if only a single message was appended. In 4688 particular, a server MUST NOT send a range such as 123:123. 4689 This is because a client that does not support [MULTIAPPEND] 4690 expects only a single UID and not a UID set. 4692 UIDs are assigned in strictly ascending order in the mailbox 4693 (refer to Section 2.3.1.1); note that a range of 12:10 is 4694 exactly equivalent to 10:12 and refers to the sequence 4695 10,11,12. 4697 This response code is returned in a tagged OK response to the 4698 APPEND command. 4700 AUTHENTICATIONFAILED 4702 Authentication failed for some reason on which the server is 4703 unwilling to elaborate. Typically, this includes "unknown 4704 user" and "bad password". 4706 This is the same as not sending any response code, except that 4707 when a client sees AUTHENTICATIONFAILED, it knows that the 4708 problem wasn't, e.g., UNAVAILABLE, so there's no point in 4709 trying the same login/password again later. 4711 C: b LOGIN "fred" "foo" 4712 S: b NO [AUTHENTICATIONFAILED] Authentication failed 4714 AUTHORIZATIONFAILED 4716 Authentication succeeded in using the authentication identity, 4717 but the server cannot or will not allow the authentication 4718 identity to act as the requested authorization identity. This 4719 is only applicable when the authentication and authorization 4720 identities are different. 4722 C: c1 AUTHENTICATE PLAIN 4723 [...] 4724 S: c1 NO [AUTHORIZATIONFAILED] No such authorization-ID 4726 C: c2 AUTHENTICATE PLAIN 4727 [...] 4728 S: c2 NO [AUTHORIZATIONFAILED] Authenticator is not an admin 4730 BADCHARSET 4732 Optionally followed by a parenthesized list of charsets. A 4733 SEARCH failed because the given charset is not supported by 4734 this implementation. If the optional list of charsets is 4735 given, this lists the charsets that are supported by this 4736 implementation. 4738 CANNOT 4740 The operation violates some invariant of the server and can 4741 never succeed. 4743 C: l create "///////" 4744 S: l NO [CANNOT] Adjacent slashes are not supported 4746 CAPABILITY 4748 Followed by a list of capabilities. This can appear in the 4749 initial OK or PREAUTH response to transmit an initial 4750 capabilities list. It can also appear in tagged responses to 4751 LOGIN or AUTHENTICATE commands. This makes it unnecessary for 4752 a client to send a separate CAPABILITY command if it recognizes 4753 this response. 4755 CLIENTBUG 4757 The server has detected a client bug. This can accompany all 4758 of OK, NO, and BAD, depending on what the client bug is. 4760 C: k1 select "/archive/projects/experiment-iv" 4761 [...] 4762 S: k1 OK [READ-ONLY] Done 4763 C: k2 status "/archive/projects/experiment-iv" (messages) 4764 [...] 4765 S: k2 OK [CLIENTBUG] Done 4767 CLOSED 4769 The CLOSED response code has no parameters. A server return 4770 the CLOSED response code when the currently selected mailbox is 4771 closed implicitly using the SELECT/EXAMINE command on another 4772 mailbox. The CLOSED response code serves as a boundary between 4773 responses for the previously opened mailbox (which was closed) 4774 and the newly selected mailbox; all responses before the CLOSED 4775 response code relate to the mailbox that was closed, and all 4776 subsequent responses relate to the newly opened mailbox. 4778 There is no need to return the CLOSED response code on 4779 completion of the CLOSE or the UNSELECT command (or similar), 4780 whose purpose is to close the currently selected mailbox 4781 without opening a new one. 4783 CONTACTADMIN 4785 The user should contact the system administrator or support 4786 desk. 4788 C: e login "fred" "foo" 4789 S: e NO [CONTACTADMIN] 4791 COPYUID 4792 Followed by the UIDVALIDITY of the destination mailbox, a UID 4793 set containing the UIDs of the message(s) in the source mailbox 4794 that were copied to the destination mailbox and containing the 4795 UIDs assigned to the copied message(s) in the destination 4796 mailbox, indicates that the message(s) have been copied to the 4797 destination mailbox with the stated UID(s). 4799 The source UID set is in the order the message(s) were copied; 4800 the destination UID set corresponds to the source UID set and 4801 is in the same order. Neither of the UID sets may contain 4802 extraneous UIDs or the symbol "*". 4804 UIDs are assigned in strictly ascending order in the mailbox 4805 (refer to Section 2.3.1.1); note that a range of 12:10 is 4806 exactly equivalent to 10:12 and refers to the sequence 4807 10,11,12. 4809 This response code is returned in a tagged OK response to the 4810 COPY/UID COPY command or in the untagged OK response to the 4811 MOVE/UID MOVE command. 4813 CORRUPTION 4815 The server discovered that some relevant data (e.g., the 4816 mailbox) are corrupt. This response code does not include any 4817 information about what's corrupt, but the server can write that 4818 to its logfiles. 4820 C: i select "/archive/projects/experiment-iv" 4821 S: i NO [CORRUPTION] Cannot open mailbox 4823 EXPIRED 4825 Either authentication succeeded or the server no longer had the 4826 necessary data; either way, access is no longer permitted using 4827 that passphrase. The client or user should get a new 4828 passphrase. 4830 C: d login "fred" "foo" 4831 S: d NO [EXPIRED] That password isn't valid any more 4833 EXPUNGEISSUED 4835 Someone else has issued an EXPUNGE for the same mailbox. The 4836 client may want to issue NOOP soon. [IMAP-MULTIACCESS] 4837 discusses this subject in depth. 4839 C: h search from fred@example.com 4840 S: * ESEARCH (TAG "h") ALL 1:3,5,8,13,21,42 4841 S: h OK [EXPUNGEISSUED] Search completed 4843 HASCHILDREN 4845 The mailbox delete operation failed because the mailbox has one 4846 or more children and the server doesn't allow deletion of 4847 mailboxes with children. 4849 C: m356 DELETE Notes 4850 S: o356 NO [HASCHILDREN] Mailbox "Notes" has children that need 4851 to be deleted first 4853 INUSE 4855 An operation has not been carried out because it involves 4856 sawing off a branch someone else is sitting on. Someone else 4857 may be holding an exclusive lock needed for this operation, or 4858 the operation may involve deleting a resource someone else is 4859 using, typically a mailbox. 4861 The operation may succeed if the client tries again later. 4863 C: g delete "/archive/projects/experiment-iv" 4864 S: g NO [INUSE] Mailbox in use 4866 LIMIT 4868 The operation ran up against an implementation limit of some 4869 kind, such as the number of flags on a single message or the 4870 number of flags used in a mailbox. 4872 C: m STORE 42 FLAGS f1 f2 f3 f4 f5 ... f250 4873 S: m NO [LIMIT] At most 32 flags in one mailbox supported 4875 NONEXISTENT 4877 The operation attempts to delete something that does not exist. 4878 Similar to ALREADYEXISTS. 4880 C: p RENAME this that 4881 S: p NO [NONEXISTENT] No such mailbox 4883 NOPERM 4885 The access control system (e.g., Access Control List (ACL), see 4886 [RFC4314] does not permit this user to carry out an operation, 4887 such as selecting or creating a mailbox. 4889 C: f select "/archive/projects/experiment-iv" 4890 S: f NO [NOPERM] Access denied 4892 OVERQUOTA 4894 The user would be over quota after the operation. (The user 4895 may or may not be over quota already.) 4897 Note that if the server sends OVERQUOTA but doesn't support the 4898 IMAP QUOTA extension defined by [RFC2087], then there is a 4899 quota, but the client cannot find out what the quota is. 4901 C: n1 uid copy 1:* oldmail 4902 S: n1 NO [OVERQUOTA] Sorry 4904 C: n2 uid copy 1:* oldmail 4905 S: n2 OK [OVERQUOTA] You are now over your soft quota 4907 PARSE 4909 The human-readable text represents an error in parsing the 4910 [RFC-5322] header or [MIME-IMB] headers of a message in the 4911 mailbox. 4913 PERMANENTFLAGS 4915 Followed by a parenthesized list of flags, indicates which of 4916 the known flags the client can change permanently. Any flags 4917 that are in the FLAGS untagged response, but not the 4918 PERMANENTFLAGS list, can not be set permanently. The 4919 PERMANENTFLAGS list can also include the special flag \*, which 4920 indicates that it is possible to create new keywords by 4921 attempting to store those keywords in the mailbox. If the 4922 client attempts to STORE a flag that is not in the 4923 PERMANENTFLAGS list, the server will either ignore the change 4924 or store the state change for the remainder of the current 4925 session only. 4927 There is no need for a server that included the special flag \* 4928 to return a new PERMANENTFLAGS response code when a new keyword 4929 was successfully set on a message upon client request. However 4930 if the server has a limit on the number of different keywords 4931 that can be stored in a mailbox and that limit is reached, the 4932 server MUST send a new PERMANENTFLAGS response code without the 4933 special flag \*. 4935 PRIVACYREQUIRED 4936 The operation is not permitted due to a lack of privacy. If 4937 Transport Layer Security (TLS) is not in use, the client could 4938 try STARTTLS (see Section 6.2.1) or alternatively reconnect to 4939 Implicit TLS port, and then repeat the operation. 4941 C: d login "fred" "foo" 4942 S: d NO [PRIVACYREQUIRED] Connection offers no privacy 4944 C: d select inbox 4945 S: d NO [PRIVACYREQUIRED] Connection offers no privacy 4947 READ-ONLY 4949 The mailbox is selected read-only, or its access while selected 4950 has changed from read-write to read-only. 4952 READ-WRITE 4954 The mailbox is selected read-write, or its access while 4955 selected has changed from read-only to read-write. 4957 SERVERBUG 4959 The server encountered a bug in itself or violated one of its 4960 own invariants. 4962 C: j select "/archive/projects/experiment-iv" 4963 S: j NO [SERVERBUG] This should not happen 4965 TRYCREATE 4967 An APPEND, COPY or MOVE attempt is failing because the target 4968 mailbox does not exist (as opposed to some other reason). This 4969 is a hint to the client that the operation can succeed if the 4970 mailbox is first created by the CREATE command. 4972 UIDNEXT 4974 Followed by a decimal number, indicates the next unique 4975 identifier value. Refer to Section 2.3.1.1 for more 4976 information. 4978 UIDNOTSTICKY 4980 The selected mailbox is supported by a mail store that does not 4981 support persistent UIDs; that is, UIDVALIDITY will be different 4982 each time the mailbox is selected. Consequently, APPEND or 4983 COPY to this mailbox will not return an APPENDUID or COPYUID 4984 response code. 4986 This response code is returned in an untagged NO response to 4987 the SELECT command. 4989 Note: servers SHOULD NOT have any UIDNOTSTICKY mail stores. 4990 This facility exists to support legacy mail stores in which 4991 it is technically infeasible to support persistent UIDs. 4992 This should be avoided when designing new mail stores. 4994 UIDVALIDITY 4996 Followed by a decimal number, indicates the unique identifier 4997 validity value. Refer to Section 2.3.1.1 for more information. 4999 UNAVAILABLE 5001 Temporary failure because a subsystem is down. For example, an 5002 IMAP server that uses a Lightweight Directory Access Protocol 5003 (LDAP) or Radius server for authentication might use this 5004 response code when the LDAP/Radius server is down. 5006 C: a LOGIN "fred" "foo" 5007 S: a NO [UNAVAILABLE] User's backend down for maintenance 5009 UNKNOWN-CTE 5011 The server does not know how to decode the section's Content- 5012 Transfer-Encoding. 5014 Client implementations MUST ignore response codes that they do not 5015 recognize. 5017 7.1.1. OK Response 5019 Contents: OPTIONAL response code 5020 human-readable text 5022 The OK response indicates an information message from the server. 5023 When tagged, it indicates successful completion of the associated 5024 command. The human-readable text MAY be presented to the user as an 5025 information message. The untagged form indicates an information-only 5026 message; the nature of the information MAY be indicated by a response 5027 code. 5029 The untagged form is also used as one of three possible greetings at 5030 connection startup. It indicates that the connection is not yet 5031 authenticated and that a LOGIN or an AUTHENTICATE command is needed. 5033 Example: S: * OK IMAP4rev2 server ready 5034 C: A001 LOGIN fred blurdybloop 5035 S: * OK [ALERT] System shutdown in 10 minutes 5036 S: A001 OK LOGIN Completed 5038 7.1.2. NO Response 5040 Contents: OPTIONAL response code 5041 human-readable text 5043 The NO response indicates an operational error message from the 5044 server. When tagged, it indicates unsuccessful completion of the 5045 associated command. The untagged form indicates a warning; the 5046 command can still complete successfully. The human-readable text 5047 describes the condition. 5049 Example: C: A222 COPY 1:2 owatagusiam 5050 S: * NO Disk is 98% full, please delete unnecessary data 5051 S: A222 OK COPY completed 5052 C: A223 COPY 3:200 blurdybloop 5053 S: * NO Disk is 98% full, please delete unnecessary data 5054 S: * NO Disk is 99% full, please delete unnecessary data 5055 S: A223 NO COPY failed: disk is full 5057 7.1.3. BAD Response 5059 Contents: OPTIONAL response code 5060 human-readable text 5062 The BAD response indicates an error message from the server. When 5063 tagged, it reports a protocol-level error in the client's command; 5064 the tag indicates the command that caused the error. The untagged 5065 form indicates a protocol-level error for which the associated 5066 command can not be determined; it can also indicate an internal 5067 server failure. The human-readable text describes the condition. 5069 Example: C: ...very long command line... 5070 S: * BAD Command line too long 5071 C: ...empty line... 5072 S: * BAD Empty command line 5073 C: A443 EXPUNGE 5074 S: * BAD Disk crash, attempting salvage to a new disk! 5075 S: * OK Salvage successful, no data lost 5076 S: A443 OK Expunge completed 5078 7.1.4. PREAUTH Response 5080 Contents: OPTIONAL response code 5081 human-readable text 5083 The PREAUTH response is always untagged, and is one of three possible 5084 greetings at connection startup. It indicates that the connection 5085 has already been authenticated by external means; thus no LOGIN/ 5086 AUTHENTICATE command is needed. 5088 Because PREAUTH moves the connection directly to the authenticated 5089 state, it effectively prevents the client from using the STARTTLS 5090 command Section 6.2.1. For this reason PREAUTH response SHOULD only 5091 be returned by servers on connections that are protected by TLS (such 5092 as on implicit TLS port [RFC8314]) or protected through other means 5093 such as IPSec. Clients that require mandatory TLS MUST close the 5094 connection after receiving PREAUTH response on a non protected port. 5096 Example: S: * PREAUTH IMAP4rev2 server logged in as Smith 5098 7.1.5. BYE Response 5100 Contents: OPTIONAL response code 5101 human-readable text 5103 The BYE response is always untagged, and indicates that the server is 5104 about to close the connection. The human-readable text MAY be 5105 displayed to the user in a status report by the client. The BYE 5106 response is sent under one of four conditions: 5108 1. as part of a normal logout sequence. The server will close the 5109 connection after sending the tagged OK response to the LOGOUT 5110 command. 5112 2. as a panic shutdown announcement. The server closes the 5113 connection immediately. 5115 3. as an announcement of an inactivity autologout. The server 5116 closes the connection immediately. 5118 4. as one of three possible greetings at connection startup, 5119 indicating that the server is not willing to accept a connection 5120 from this client. The server closes the connection immediately. 5122 The difference between a BYE that occurs as part of a normal LOGOUT 5123 sequence (the first case) and a BYE that occurs because of a failure 5124 (the other three cases) is that the connection closes immediately in 5125 the failure case. In all cases the client SHOULD continue to read 5126 response data from the server until the connection is closed; this 5127 will ensure that any pending untagged or completion responses are 5128 read and processed. 5130 Example: S: * BYE Autologout; idle for too long 5132 7.2. Server Responses - Server Status 5134 These responses are always untagged. This is how server and mailbox 5135 status data are transmitted from the server to the client. 5137 7.2.1. ENABLED Response 5139 Contents: capability listing 5141 The ENABLED response occurs as a result of an ENABLE command. The 5142 capability listing contains a space-separated listing of capability 5143 names that the server supports and that were successfully enabled. 5144 The ENABLED response may contain no capabilities, which means that no 5145 extensions listed by the client were successfully enabled. 5147 Example: S: * ENABLED CONDSTORE QRESYNC 5149 7.2.2. CAPABILITY Response 5151 Contents: capability listing 5153 The CAPABILITY response occurs as a result of a CAPABILITY command. 5154 The capability listing contains a space-separated listing of 5155 capability names that the server supports. The capability listing 5156 MUST include the atom "IMAP4rev2", but note that it doesn't have to 5157 be the first capability listed. The order of capability names has no 5158 significance. 5160 In addition, client and server implementations MUST implement the 5161 "STARTTLS", "LOGINDISABLED", and "AUTH=PLAIN" (described in [PLAIN]) 5162 capabilities. See the Security Considerations (Section 11) for 5163 important information related to these capabilities. 5165 A capability name which begins with "AUTH=" indicates that the server 5166 supports that particular authentication mechanism [SASL]. 5168 The LOGINDISABLED capability indicates that the LOGIN command is 5169 disabled, and that the server will respond with a tagged NO response 5170 to any attempt to use the LOGIN command even if the user name and 5171 password are valid. An IMAP client MUST NOT issue the LOGIN command 5172 if the server advertises the LOGINDISABLED capability. 5174 Other capability names indicate that the server supports an 5175 extension, revision, or amendment to the IMAP4rev2 protocol. Server 5176 responses MUST conform to this document until the client issues a 5177 command that uses the associated capability. 5179 Capability names SHOULD be registered with IANA using RFC Required 5180 policy. A server SHOULD NOT offer unregistered capability names. 5182 Client implementations SHOULD NOT require any capability name other 5183 than "IMAP4rev2", and possibly "STARTTLS" and "LOGINDISABLED" (on a 5184 non implicit TLS port). Client implementations MUST ignore any 5185 unknown capability names. 5187 A server MAY send capabilities automatically, by using the CAPABILITY 5188 response code in the initial PREAUTH or OK responses, and by sending 5189 an updated CAPABILITY response code in the tagged OK response as part 5190 of a successful authentication. It is unnecessary for a client to 5191 send a separate CAPABILITY command if it recognizes these automatic 5192 capabilities. 5194 The list of capabilities returned by a server MAY change during the 5195 connection. In particular, it is quite common for the server to 5196 change list of capabilities after successful TLS negotiation 5197 (STARTTLS command) and/or after successful authentication 5198 (AUTHENTICATE or LOGIN commands). 5200 Example: S: * CAPABILITY STARTTLS AUTH=GSSAPI IMAP4rev2 LOGINDISABLED 5201 XPIG-LATIN 5203 Note that in the above example XPIG-LATIN is a fictitious capability 5204 name. 5206 7.3. Server Responses - Mailbox Status 5208 These responses are always untagged. This is how server and mailbox 5209 status data are transmitted from the server to the client. Many of 5210 these responses typically result from a command with the same name. 5212 7.3.1. LIST Response 5214 Contents: name attributes 5215 hierarchy delimiter 5216 name 5217 OPTIONAL extension data 5219 The LIST response occurs as a result of a LIST command. It returns a 5220 single name that matches the LIST specification. There can be 5221 multiple LIST responses for a single LIST command. 5223 The following base mailbox name attributes are defined: 5225 \NonExistent The "\NonExistent" attribute indicates that a mailbox 5226 name does not refer to an existing mailbox. Note that this 5227 attribute is not meaningful by itself, as mailbox names that match 5228 the canonical LIST pattern but don't exist must not be returned 5229 unless one of the two conditions listed below is also satisfied: 5231 1. The mailbox name also satisfies the selection criteria (for 5232 example, it is subscribed and the "SUBSCRIBED" selection 5233 option has been specified). 5235 2. "RECURSIVEMATCH" has been specified, and the mailbox name has 5236 at least one descendant mailbox name that does not match the 5237 LIST pattern and does match the selection criteria. 5239 In practice, this means that the "\NonExistent" attribute is 5240 usually returned with one or more of "\Subscribed", "\Remote", 5241 "\HasChildren", or the CHILDINFO extended data item. 5243 The "\NonExistent" attribute implies "\NoSelect". 5245 \Noinferiors It is not possible for any child levels of hierarchy to 5246 exist under this name; no child levels exist now and none can be 5247 created in the future. 5249 \Noselect It is not possible to use this name as a selectable 5250 mailbox. 5252 \HasChildren The presence of this attribute indicates that the 5253 mailbox has child mailboxes. A server SHOULD NOT set this 5254 attribute if there are child mailboxes and the user does not have 5255 permission to access any of them. In this case, \HasNoChildren 5256 SHOULD be used. In many cases, however, a server may not be able 5257 to efficiently compute whether a user has access to any child 5258 mailbox. Note that even though the \HasChildren attribute for a 5259 mailbox must be correct at the time of processing of the mailbox, 5260 a client must be prepared to deal with a situation when a mailbox 5261 is marked with the \HasChildren attribute, but no child mailbox 5262 appears in the response to the LIST command. This might happen, 5263 for example, due to children mailboxes being deleted or made 5264 inaccessible to the user (using access control) by another client 5265 before the server is able to list them. 5267 \HasNoChildren The presence of this attribute indicates that the 5268 mailbox has NO child mailboxes that are accessible to the 5269 currently authenticated user. 5271 \Marked The mailbox has been marked "interesting" by the server; the 5272 mailbox probably contains messages that have been added since the 5273 last time the mailbox was selected. 5275 \Unmarked The mailbox does not contain any additional messages since 5276 the last time the mailbox was selected. 5278 \Subscribed The mailbox name was subscribed to using the SUBSCRIBE 5279 command. 5281 \Remote The mailbox is a remote mailbox. 5283 It is an error for the server to return both a \HasChildren and a 5284 \HasNoChildren attribute in the same LIST response. A client that 5285 encounters a LIST response with both \HasChildren and \HasNoChildren 5286 attributes present should act as if both are absent in the LIST 5287 response. 5289 Note: the \HasNoChildren attribute should not be confused with the 5290 \NoInferiors attribute, which indicates that no child mailboxes 5291 exist now and none can be created in the future. 5293 If it is not feasible for the server to determine whether or not the 5294 mailbox is "interesting", the server SHOULD NOT send either \Marked 5295 or \Unmarked. The server MUST NOT send more than one of \Marked, 5296 \Unmarked, and \Noselect for a single mailbox, and MAY send none of 5297 these. 5299 In addition to the base mailbox name attributes defined above, an 5300 IMAP server MAY also include any or all of the following attributes 5301 that denote "role" (or "special-use") of a mailbox. These attributes 5302 are included along with base attributes defined above. A given 5303 mailbox may have none, one, or more than one of these attributes. In 5304 some cases, a special use is advice to a client about what to put in 5305 that mailbox. In other cases, it's advice to a client about what to 5306 expect to find there. 5308 \All This mailbox presents all messages in the user's message store. 5309 Implementations MAY omit some messages, such as, perhaps, those in 5310 \Trash and \Junk. When this special use is supported, it is 5311 almost certain to represent a virtual mailbox. 5313 \Archive This mailbox is used to archive messages. The meaning of 5314 an "archival" mailbox is server-dependent; typically, it will be 5315 used to get messages out of the inbox, or otherwise keep them out 5316 of the user's way, while still making them accessible. 5318 \Drafts This mailbox is used to hold draft messages -- typically, 5319 messages that are being composed but have not yet been sent. In 5320 some server implementations, this might be a virtual mailbox, 5321 containing messages from other mailboxes that are marked with the 5322 "\Draft" message flag. Alternatively, this might just be advice 5323 that a client put drafts here. 5325 \Flagged This mailbox presents all messages marked in some way as 5326 "important". When this special use is supported, it is likely to 5327 represent a virtual mailbox collecting messages (from other 5328 mailboxes) that are marked with the "\Flagged" message flag. 5330 \Junk This mailbox is where messages deemed to be junk mail are 5331 held. Some server implementations might put messages here 5332 automatically. Alternatively, this might just be advice to a 5333 client-side spam filter. 5335 \Sent This mailbox is used to hold copies of messages that have been 5336 sent. Some server implementations might put messages here 5337 automatically. Alternatively, this might just be advice that a 5338 client save sent messages here. 5340 \Trash This mailbox is used to hold messages that have been deleted 5341 or marked for deletion. In some server implementations, this 5342 might be a virtual mailbox, containing messages from other 5343 mailboxes that are marked with the "\Deleted" message flag. 5344 Alternatively, this might just be advice that a client that 5345 chooses not to use the IMAP "\Deleted" model should use this as 5346 its trash location. In server implementations that strictly 5347 expect the IMAP "\Deleted" model, this special use is likely not 5348 to be supported. 5350 All of special-use attributes are OPTIONAL, and any given server or 5351 message store may support any combination of the attributes, or none 5352 at all. In most cases, there will likely be at most one mailbox with 5353 a given attribute for a given user, but in some server or message 5354 store implementations it might be possible for multiple mailboxes to 5355 have the same special-use attribute. 5357 Special-use attributes are likely to be user-specific. User Adam 5358 might share his \Sent mailbox with user Barb, but that mailbox is 5359 unlikely to also serve as Barb's \Sent mailbox. 5361 Other mailbox name attributes can be found in the "IMAP Mailbox Name 5362 Attributes" registry [IMAP-MAILBOX-NAME-ATTRS-REG]. 5364 The hierarchy delimiter is a character used to delimit levels of 5365 hierarchy in a mailbox name. A client can use it to create child 5366 mailboxes, and to search higher or lower levels of naming hierarchy. 5367 All children of a top-level hierarchy node MUST use the same 5368 separator character. A NIL hierarchy delimiter means that no 5369 hierarchy exists; the name is a "flat" name. 5371 The name represents an unambiguous left-to-right hierarchy, and MUST 5372 be valid for use as a reference in LIST command. Unless \Noselect or 5373 \NonExistent is indicated, the name MUST also be valid as an argument 5374 for commands, such as SELECT, that accept mailbox names. 5376 The name might be followed by an OPTIONAL series of extended fields, 5377 a parenthesized list of tagged data (also referred to as "extended 5378 data item"). The first element of an extended field is a string, 5379 which identifies the type of data. [RFC5258] specified requirements 5380 on string registration (which are called "tags" there; such tags are 5381 not to be confused with IMAP command tags), in particular it said 5382 that "Tags MUST be registered with IANA". This document doesn't 5383 change that. See Section 9.5 of [RFC5258] for the registration 5384 template. The server MAY return data in the extended fields that was 5385 not directly solicited by the client in the corresponding LIST 5386 command. For example, the client can enable extra extended fields by 5387 using another IMAP extension that make use of the extended LIST 5388 responses. The client MUST ignore all extended fields it doesn't 5389 recognize. 5391 Example: S: * LIST (\Noselect) "/" ~/Mail/foo 5393 Example: S: * LIST (\Marked) ":" Tables (tablecloth (("edge" "lacy") 5394 ("color" "red")) Sample "text") 5395 S: * LIST () ":" Tables:new (tablecloth ("edge" "lacy") 5396 Sample ("text" "more text")) 5398 7.3.2. NAMESPACE Response 5400 Contents: the prefix and hierarchy delimiter to the server's 5401 Personal Namespace(s), Other Users' Namespace(s), and 5402 Shared Namespace(s) 5404 The NAMESPACE response occurs as a result of a NAMESPACE command. It 5405 contains the prefix and hierarchy delimiter to the server's Personal 5406 Namespace(s), Other Users' Namespace(s), and Shared Namespace(s) that 5407 the server wishes to expose. The response will contain a NIL for any 5408 namespace class that is not available. Namespace-Response-Extensions 5409 ABNF non terminal is defined for extensibility and MAY be included in 5410 the response. 5412 Example: S: * NAMESPACE (("" "/")) (("~" "/")) NIL 5414 7.3.3. STATUS Response 5416 Contents: name 5417 status parenthesized list 5419 The STATUS response occurs as a result of an STATUS command. It 5420 returns the mailbox name that matches the STATUS specification and 5421 the requested mailbox status information. 5423 Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292) 5425 7.3.4. ESEARCH Response 5427 Contents: one or more search-return-data pairs 5429 The ESEARCH response occurs as a result of a SEARCH or UID SEARCH 5430 command. 5432 The ESEARCH response starts with an optional search correlator. If 5433 it is missing, then the response was not caused by a particular IMAP 5434 command, whereas if it is present, it contains the tag of the command 5435 that caused the response to be returned. 5437 The search correlator is followed by an optional UID indicator. If 5438 this indicator is present, all data in the ESEARCH response refers to 5439 UIDs, otherwise all returned data refers to message numbers. 5441 The rest of the ESEARCH response contains one or more search data 5442 pairs. Each pair starts with unique return item name, followed by a 5443 space and the corresponding data. Search data pairs may be returned 5444 in any order. Unless specified otherwise by an extension, any return 5445 item name SHOULD appear only once in an ESEARCH response. 5447 [[TBD: describe the most common search data pairs returned.]] 5449 Example: S: * ESEARCH UID COUNT 5 ALL 4:19,21,28 5451 Example: S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28 5453 Example: S: * ESEARCH COUNT 5 ALL 1:17,21 5455 7.3.5. FLAGS Response 5457 Contents: flag parenthesized list 5459 The FLAGS response occurs as a result of a SELECT or EXAMINE command. 5460 The flag parenthesized list identifies the flags (at a minimum, the 5461 system-defined flags) that are applicable for this mailbox. Flags 5462 other than the system flags can also exist, depending on server 5463 implementation. 5465 The update from the FLAGS response MUST be remembered by the client. 5467 Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 5469 7.4. Server Responses - Mailbox Size 5471 These responses are always untagged. This is how changes in the size 5472 of the mailbox are transmitted from the server to the client. 5473 Immediately following the "*" token is a number that represents a 5474 message count. 5476 7.4.1. EXISTS Response 5478 Contents: none 5480 The EXISTS response reports the number of messages in the mailbox. 5481 This response occurs as a result of a SELECT or EXAMINE command, and 5482 if the size of the mailbox changes (e.g., new messages). 5484 The update from the EXISTS response MUST be remembered by the client. 5486 Example: S: * 23 EXISTS 5488 7.5. Server Responses - Message Status 5490 These responses are always untagged. This is how message data are 5491 transmitted from the server to the client, often as a result of a 5492 command with the same name. Immediately following the "*" token is a 5493 number that represents a message sequence number. 5495 7.5.1. EXPUNGE Response 5497 Contents: none 5499 The EXPUNGE response reports that the specified message sequence 5500 number has been permanently removed from the mailbox. The message 5501 sequence number for each successive message in the mailbox is 5502 immediately decremented by 1, and this decrement is reflected in 5503 message sequence numbers in subsequent responses (including other 5504 untagged EXPUNGE responses). 5506 The EXPUNGE response also decrements the number of messages in the 5507 mailbox; it is not necessary to send an EXISTS response with the new 5508 value. 5510 As a result of the immediate decrement rule, message sequence numbers 5511 that appear in a set of successive EXPUNGE responses depend upon 5512 whether the messages are removed starting from lower numbers to 5513 higher numbers, or from higher numbers to lower numbers. For 5514 example, if the last 5 messages in a 9-message mailbox are expunged, 5515 a "lower to higher" server will send five untagged EXPUNGE responses 5516 for message sequence number 5, whereas a "higher to lower server" 5517 will send successive untagged EXPUNGE responses for message sequence 5518 numbers 9, 8, 7, 6, and 5. 5520 An EXPUNGE response MUST NOT be sent when no command is in progress, 5521 nor while responding to a FETCH, STORE, or SEARCH command. This rule 5522 is necessary to prevent a loss of synchronization of message sequence 5523 numbers between client and server. A command is not "in progress" 5524 until the complete command has been received; in particular, a 5525 command is not "in progress" during the negotiation of command 5526 continuation. 5528 Note: UID FETCH, UID STORE, and UID SEARCH are different commands 5529 from FETCH, STORE, and SEARCH. An EXPUNGE response MAY be sent 5530 during a UID command. 5532 The update from the EXPUNGE response MUST be remembered by the 5533 client. 5535 Example: S: * 44 EXPUNGE 5537 7.5.2. FETCH Response 5539 Contents: message data 5541 The FETCH response returns data about a message to the client. The 5542 data are pairs of data item names and their values in parentheses. 5543 This response occurs as the result of a FETCH or STORE command, as 5544 well as by unilateral server decision (e.g., flag updates). 5546 The current data items are: 5548 BINARY[]<> 5550 An or expressing the content of the 5551 specified section after removing any Content-Transfer-Encoding- 5552 related encoding. If is present it refers to the 5553 offset within the DECODED section data. 5555 If the domain of the decoded data is "8bit" and the data does 5556 not contain the NUL octet, the server SHOULD return the data in 5557 a instead of a ; this allows the client to 5558 determine if the "8bit" data contains the NUL octet without 5559 having to explicitly scan the data stream for for NULs. 5561 Messaging clients and servers have been notoriously lax in 5562 their adherence to the Internet CRLF convention for terminating 5563 lines of textual data (text/* media types) in Internet 5564 protocols. When sending data in BINARY[...] FETCH data item, 5565 servers MUST ensure that textual line-oriented sections are 5566 always transmitted using the IMAP4 CRLF line termination 5567 syntax, regardless of the underlying storage representation of 5568 the data on the server. 5570 If the server does not know how to decode the section's 5571 Content-Transfer-Encoding, it MUST fail the request and issue a 5572 "NO" response that contains the "UNKNOWN-CTE" response code. 5574 BINARY.SIZE[] 5576 The size of the section after removing any Content-Transfer- 5577 Encoding-related encoding. The value returned MUST match the 5578 size of the or that will be returned by 5579 the corresponding FETCH BINARY request. 5581 If the server does not know how to decode the section's 5582 Content-Transfer-Encoding, it MUST fail the request and issue a 5583 "NO" response that contains the "UNKNOWN-CTE" response code. 5585 BODY A form of BODYSTRUCTURE without extension data. 5587 BODY[
]<> 5589 A string expressing the body contents of the specified section. 5590 The string SHOULD be interpreted by the client according to the 5591 content transfer encoding, body type, and subtype. 5593 If the origin octet is specified, this string is a substring of 5594 the entire body contents, starting at that origin octet. This 5595 means that BODY[]<0> MAY be truncated, but BODY[] is NEVER 5596 truncated. 5598 Note: The origin octet facility MUST NOT be used by a server 5599 in a FETCH response unless the client specifically requested 5600 it by means of a FETCH of a BODY[
]<> data 5601 item. 5603 8-bit textual data is permitted if a [CHARSET] identifier is 5604 part of the body parameter parenthesized list for this section. 5605 Note that headers (part specifiers HEADER or MIME, or the 5606 header portion of a MESSAGE/RFC822 or MESSAGE/GLOBAL part), MAY 5607 be in UTF-8. Note also that the [RFC-5322] delimiting blank 5608 line between the header and the body is not affected by header 5609 line subsetting; the blank line is always included as part of 5610 header data, except in the case of a message which has no body 5611 and no blank line. 5613 Non-textual data such as binary data MUST be transfer encoded 5614 into a textual form, such as BASE64, prior to being sent to the 5615 client. To derive the original binary data, the client MUST 5616 decode the transfer encoded string. 5618 BODYSTRUCTURE 5620 A parenthesized list that describes the [MIME-IMB] body 5621 structure of a message. This is computed by the server by 5622 parsing the [MIME-IMB] header fields, defaulting various fields 5623 as necessary. 5625 For example, a simple text message of 48 lines and 2279 octets 5626 can have a body structure of: ("TEXT" "PLAIN" ("CHARSET" "US- 5627 ASCII") NIL NIL "7BIT" 2279 48) 5629 Multiple parts are indicated by parenthesis nesting. Instead 5630 of a body type as the first element of the parenthesized list, 5631 there is a sequence of one or more nested body structures. The 5632 second element of the parenthesized list is the multipart 5633 subtype (mixed, digest, parallel, alternative, etc.). 5635 For example, a two part message consisting of a text and a 5636 BASE64-encoded text attachment can have a body structure of: 5637 (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 5638 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff") 5639 "<960723163407.20117h@cac.washington.edu>" "Compiler diff" 5640 "BASE64" 4554 73) "MIXED") 5642 Extension data follows the multipart subtype. Extension data 5643 is never returned with the BODY fetch, but can be returned with 5644 a BODYSTRUCTURE fetch. Extension data, if present, MUST be in 5645 the defined order. The extension data of a multipart body part 5646 are in the following order: 5648 body parameter parenthesized list A parenthesized list of 5649 attribute/value pairs [e.g., ("foo" "bar" "baz" "rag") where 5650 "bar" is the value of "foo", and "rag" is the value of 5651 "baz"] as defined in [MIME-IMB]. Servers SHOULD decode 5652 parameter value continuations and parameter value character 5653 sets as described in [RFC2231], for example, if the message 5654 contains parameters "baz*0", "baz*1" and "baz*2", the server 5655 should RFC2231-decode them, concatenate and return the 5656 resulting value as a parameter "baz". Similarly, if the 5657 message contains parameters "foo*0*" and "foo*1*", the 5658 server should RFC2231-decode them, convert to UTF-8, 5659 concatenate and return the resulting value as a parameter 5660 "foo*". 5662 body disposition A parenthesized list, consisting of a 5663 disposition type string, followed by a parenthesized list of 5664 disposition attribute/value pairs as defined in 5665 [DISPOSITION]. Servers SHOULD decode parameter value 5666 continuations as described in [RFC2231]. 5668 body language A string or parenthesized list giving the body 5669 language value as defined in [LANGUAGE-TAGS]. 5671 body location A string giving the body content URI as defined 5672 in [LOCATION]. 5674 Any following extension data are not yet defined in this 5675 version of the protocol. Such extension data can consist of 5676 zero or more NILs, strings, numbers, or potentially nested 5677 parenthesized lists of such data. Client implementations that 5678 do a BODYSTRUCTURE fetch MUST be prepared to accept such 5679 extension data. Server implementations MUST NOT send such 5680 extension data until it has been defined by a revision of this 5681 protocol. 5683 The basic fields of a non-multipart body part are in the 5684 following order: 5686 body type A string giving the content media type name as 5687 defined in [MIME-IMB]. 5689 body subtype A string giving the content subtype name as 5690 defined in [MIME-IMB]. 5692 body parameter parenthesized list A parenthesized list of 5693 attribute/value pairs [e.g., ("foo" "bar" "baz" "rag") where 5694 "bar" is the value of "foo" and "rag" is the value of "baz"] 5695 as defined in [MIME-IMB]. 5697 body id A string giving the Content-ID header field value as 5698 defined in Section 7 of [MIME-IMB]. 5700 body description A string giving the Content-Description 5701 header field value as defined in Section 8 of [MIME-IMB]. 5703 body encoding A string giving the content transfer encoding as 5704 defined in Section 6 of [MIME-IMB]. 5706 body size A number giving the size of the body in octets. 5707 Note that this size is the size in its transfer encoding and 5708 not the resulting size after any decoding. 5710 A body type of type MESSAGE and subtype RFC822 contains, 5711 immediately after the basic fields, the envelope structure, 5712 body structure, and size in text lines of the encapsulated 5713 message. 5715 A body type of type TEXT contains, immediately after the basic 5716 fields, the size of the body in text lines. Note that this 5717 size is the size in its content transfer encoding and not the 5718 resulting size after any decoding. 5720 Extension data follows the basic fields and the type-specific 5721 fields listed above. Extension data is never returned with the 5722 BODY fetch, but can be returned with a BODYSTRUCTURE fetch. 5723 Extension data, if present, MUST be in the defined order. 5725 The extension data of a non-multipart body part are in the 5726 following order: 5728 body MD5 A string giving the body MD5 value as defined in 5729 [MD5]. 5731 body disposition A parenthesized list with the same content 5732 and function as the body disposition for a multipart body 5733 part. 5735 body language A string or parenthesized list giving the body 5736 language value as defined in [LANGUAGE-TAGS]. 5738 body location A string giving the body content URI as defined 5739 in [LOCATION]. 5741 Any following extension data are not yet defined in this 5742 version of the protocol, and would be as described above under 5743 multipart extension data. 5745 ENVELOPE 5747 A parenthesized list that describes the envelope structure of a 5748 message. This is computed by the server by parsing the 5749 [RFC-5322] header into the component parts, defaulting various 5750 fields as necessary. 5752 The fields of the envelope structure are in the following 5753 order: date, subject, from, sender, reply-to, to, cc, bcc, in- 5754 reply-to, and message-id. The date, subject, in-reply-to, and 5755 message-id fields are strings. The from, sender, reply-to, to, 5756 cc, and bcc fields are parenthesized lists of address 5757 structures. 5759 An address structure is a parenthesized list that describes an 5760 electronic mail address. The fields of an address structure 5761 are in the following order: personal name, [SMTP] at-domain- 5762 list (source route, obs-route), mailbox name, and host name. 5764 [RFC-5322] group syntax is indicated by a special form of 5765 address structure in which the host name field is NIL. If the 5766 mailbox name field is also NIL, this is an end of group marker 5767 (semi-colon in RFC 822 syntax). If the mailbox name field is 5768 non-NIL, this is a start of group marker, and the mailbox name 5769 field holds the group name phrase. 5771 If the Date, Subject, In-Reply-To, and Message-ID header fields 5772 are absent in the [RFC-5322] header, the corresponding member 5773 of the envelope is NIL; if these header fields are present but 5774 empty the corresponding member of the envelope is the empty 5775 string. 5777 Note: some servers may return a NIL envelope member in the 5778 "present but empty" case. Clients SHOULD treat NIL and 5779 empty string as identical. 5781 Note: [RFC-5322] requires that all messages have a valid 5782 Date header field. Therefore, for a well-formed message the 5783 date member in the envelope can not be NIL or the empty 5784 string. However it can be NIL for a malformed or a draft 5785 message. 5787 Note: [RFC-5322] requires that the In-Reply-To and Message- 5788 ID header fields, if present, have non-empty content. 5789 Therefore, for a well-formed message the in-reply-to and 5790 message-id members in the envelope can not be the empty 5791 string. However they can still be the empty string for a 5792 malformed message. 5794 If the From, To, Cc, and Bcc header fields are absent in the 5795 [RFC-5322] header, or are present but empty, the corresponding 5796 member of the envelope is NIL. 5798 If the Sender or Reply-To header fields are absent in the 5799 [RFC-5322] header, or are present but empty, the server sets 5800 the corresponding member of the envelope to be the same value 5801 as the from member (the client is not expected to know to do 5802 this). 5804 Note: [RFC-5322] requires that all messages have a valid 5805 From header field. Therefore, for a well-formed message the 5806 from, sender, and reply-to members in the envelope can not 5807 be NIL. However they can be NIL for a malformed or a draft 5808 message. 5810 FLAGS A parenthesized list of flags that are set for this message. 5812 INTERNALDATE A string representing the internal date of the message. 5814 RFC822.SIZE A number expressing the [RFC-5322] size of the message. 5816 UID A number expressing the unique identifier of the message. 5818 If the server chooses to send unsolicited FETCH responses, they MUST 5819 include UID FETCH item. Note that this is a new requirement when 5820 compared to RFC 3501. 5822 Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827) 5824 7.6. Server Responses - Command Continuation Request 5826 The command continuation request response is indicated by a "+" token 5827 instead of a tag. This form of response indicates that the server is 5828 ready to accept the continuation of a command from the client. The 5829 remainder of this response is a line of text. 5831 This response is used in the AUTHENTICATE command to transmit server 5832 data to the client, and request additional client data. This 5833 response is also used if an argument to any command is a 5834 synchronizing literal. 5836 The client is not permitted to send the octets of the synchronizing 5837 literal unless the server indicates that it is expected. This 5838 permits the server to process commands and reject errors on a line- 5839 by-line basis. The remainder of the command, including the CRLF that 5840 terminates a command, follows the octets of the literal. If there 5841 are any additional command arguments, the literal octets are followed 5842 by a space and those arguments. 5844 Example: C: A001 LOGIN {11} 5845 S: + Ready for additional command text 5846 C: FRED FOOBAR {7} 5847 S: + Ready for additional command text 5848 C: fat man 5849 S: A001 OK LOGIN completed 5850 C: A044 BLURDYBLOOP {102856} 5851 S: A044 BAD No such command as "BLURDYBLOOP" 5853 8. Sample IMAP4rev2 connection 5855 The following is a transcript of an IMAP4rev2 connection. A long 5856 line in this sample is broken for editorial clarity. 5858 S: * OK IMAP4rev2 Service Ready 5859 C: a001 login mrc secret 5860 S: a001 OK LOGIN completed 5861 C: a002 select inbox 5862 S: * 18 EXISTS 5863 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 5864 S: * OK [UIDVALIDITY 3857529045] UIDs valid 5865 S: * LIST () "/" INBOX ("OLDNAME" ("inbox")) 5866 S: a002 OK [READ-WRITE] SELECT completed 5867 C: a003 fetch 12 full 5868 S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700" 5869 RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)" 5870 "IMAP4rev2 WG mtg summary and minutes" 5871 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5872 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5873 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5874 ((NIL NIL "imap" "cac.washington.edu")) 5875 ((NIL NIL "minutes" "CNRI.Reston.VA.US") 5876 ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL 5877 "") 5878 BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 5879 92)) 5880 S: a003 OK FETCH completed 5881 C: a004 fetch 12 body[header] 5882 S: * 12 FETCH (BODY[HEADER] {342} 5883 S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT) 5884 S: From: Terry Gray 5885 S: Subject: IMAP4rev2 WG mtg summary and minutes 5886 S: To: imap@cac.washington.edu 5887 S: cc: minutes@CNRI.Reston.VA.US, John Klensin 5888 S: Message-Id: 5889 S: MIME-Version: 1.0 5890 S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 5891 S: 5892 S: ) 5893 S: a004 OK FETCH completed 5894 C: a005 store 12 +flags \deleted 5895 S: * 12 FETCH (FLAGS (\Seen \Deleted)) 5896 S: a005 OK +FLAGS completed 5897 C: a006 logout 5898 S: * BYE IMAP4rev2 server terminating connection 5899 S: a006 OK LOGOUT completed 5901 9. Formal Syntax 5903 The following syntax specification uses the Augmented Backus-Naur 5904 Form (ABNF) notation as specified in [ABNF]. 5906 In the case of alternative or optional rules in which a later rule 5907 overlaps an earlier rule, the rule which is listed earlier MUST take 5908 priority. For example, "\Seen" when parsed as a flag is the \Seen 5909 flag name and not a flag-extension, even though "\Seen" can be parsed 5910 as a flag-extension. Some, but not all, instances of this rule are 5911 noted below. 5913 Note: [ABNF] rules MUST be followed strictly; in particular: 5915 (1) Except as noted otherwise, all alphabetic characters are case- 5916 insensitive. The use of upper or lower case characters to define 5917 token strings is for editorial clarity only. Implementations MUST 5918 accept these strings in a case-insensitive fashion. 5920 (2) In all cases, SP refers to exactly one space. It is NOT 5921 permitted to substitute TAB, insert additional spaces, or 5922 otherwise treat SP as being equivalent to LWSP. 5924 (3) The ASCII NUL character, %x00, MUST NOT be used anywhere, with 5925 the exception of the OCTET production. 5927 SP = 5928 CTL = 5929 CRLF = 5930 ALPHA = 5931 DIGIT = 5932 DQUOTE = 5933 OCTET = 5935 address = "(" addr-name SP addr-adl SP addr-mailbox SP 5936 addr-host ")" 5938 addr-adl = nstring 5939 ; Holds route from [RFC-5322] obs-route if 5940 ; non-NIL 5942 addr-host = nstring 5943 ; NIL indicates [RFC-5322] group syntax. 5944 ; Otherwise, holds [RFC-5322] domain name 5946 addr-mailbox = nstring 5947 ; NIL indicates end of [RFC-5322] group; if 5948 ; non-NIL and addr-host is NIL, holds 5949 ; [RFC-5322] group name. 5950 ; Otherwise, holds [RFC-5322] local-part 5951 ; after removing [RFC-5322] quoting 5953 addr-name = nstring 5954 ; If non-NIL, holds phrase from [RFC-5322] 5955 ; mailbox after removing [RFC-5322] quoting 5957 append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP 5958 literal 5960 append-uid = uniqueid 5962 astring = 1*ASTRING-CHAR / string 5964 ASTRING-CHAR = ATOM-CHAR / resp-specials 5966 atom = 1*ATOM-CHAR 5968 ATOM-CHAR = 5970 atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards / 5971 quoted-specials / resp-specials 5973 authenticate = "AUTHENTICATE" SP auth-type [SP initial-resp] 5974 *(CRLF base64) 5976 auth-type = atom 5977 ; Defined by [SASL] 5979 base64 = *(4base64-char) [base64-terminal] 5981 base64-char = ALPHA / DIGIT / "+" / "/" 5982 ; Case-sensitive 5984 base64-terminal = (2base64-char "==") / (3base64-char "=") 5986 body = "(" (body-type-1part / body-type-mpart) ")" 5988 body-extension = nstring / number / number64 / 5989 "(" body-extension *(SP body-extension) ")" 5990 ; Future expansion. Client implementations 5991 ; MUST accept body-extension fields. Server 5992 ; implementations MUST NOT generate 5993 ; body-extension fields except as defined by 5994 ; future standard or standards-track 5995 ; revisions of this specification. 5997 body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang 5998 [SP body-fld-loc *(SP body-extension)]]] 5999 ; MUST NOT be returned on non-extensible 6000 ; "BODY" fetch 6002 body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang 6003 [SP body-fld-loc *(SP body-extension)]]] 6004 ; MUST NOT be returned on non-extensible 6005 ; "BODY" fetch 6007 body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP 6008 body-fld-enc SP body-fld-octets 6010 body-fld-desc = nstring 6012 body-fld-dsp = "(" string SP body-fld-param ")" / nil 6014 body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/ 6015 "QUOTED-PRINTABLE") DQUOTE) / string 6016 ; Content-Transfer-Encoding header field value. 6017 ; Defaults to "7BIT" (as per RFC 2045) 6018 ; if not present in the body part. 6020 body-fld-id = nstring 6022 body-fld-lang = nstring / "(" string *(SP string) ")" 6024 body-fld-loc = nstring 6026 body-fld-lines = number64 6028 body-fld-md5 = nstring 6030 body-fld-octets = number 6032 body-fld-param = "(" string SP string *(SP string SP string) ")" / nil 6034 body-type-1part = (body-type-basic / body-type-msg / body-type-text) 6035 [SP body-ext-1part] 6037 body-type-basic = media-basic SP body-fields 6038 ; MESSAGE subtype MUST NOT be "RFC822" or "GLOBAL" 6040 body-type-mpart = 1*body SP media-subtype 6041 [SP body-ext-mpart] 6042 ; MULTIPART body part 6044 body-type-msg = media-message SP body-fields SP envelope 6045 SP body SP body-fld-lines 6047 body-type-text = media-text SP body-fields SP body-fld-lines 6049 capability = ("AUTH=" auth-type) / atom 6050 ; New capabilities MUST begin with "X" or be 6051 ; registered with IANA in 6052 ; a standards-track, an experimental 6053 ; or an informational RFC. 6055 capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev2" 6056 *(SP capability) 6057 ; Servers MUST implement the STARTTLS, AUTH=PLAIN, 6058 ; and LOGINDISABLED capabilities. 6059 ; Servers which offer RFC 1730 compatibility MUST 6060 ; list "IMAP4" as the first capability. 6061 ; Servers which offer RFC 3501 compatibility MUST 6062 ; list "IMAP4rev1" as one of capabilities. 6064 CHAR = 6066 CHAR8 = %x01-ff 6067 ; any OCTET except NUL, %x00 6069 charset = atom / quoted 6071 childinfo-extended-item = "CHILDINFO" SP "(" 6072 list-select-base-opt-quoted 6073 *(SP list-select-base-opt-quoted) ")" 6074 ; Extended data item (mbox-list-extended-item) 6075 ; returned when the RECURSIVEMATCH 6076 ; selection option is specified. 6077 ; Note 1: the CHILDINFO extended data item tag can be 6078 ; returned with and without surrounding quotes, as per 6079 ; mbox-list-extended-item-tag production. 6080 ; Note 2: The selection options are always returned 6081 ; quoted, unlike their specification in 6082 ; the extended LIST command. 6084 child-mbox-flag = "\HasChildren" / "\HasNoChildren" 6085 ; attributes for CHILDREN return option, at most one 6086 ; possible per LIST response 6088 command = tag SP (command-any / command-auth / command-nonauth / 6089 command-select) CRLF 6090 ; Modal based on state 6092 command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / x-command 6093 ; Valid in all states 6095 command-auth = append / create / delete / enable / examine / list / 6096 Namespace-Command / 6097 rename / select / status / subscribe / unsubscribe / 6098 idle 6099 ; Valid only in Authenticated or Selected state 6101 command-nonauth = login / authenticate / "STARTTLS" 6102 ; Valid only when in Not Authenticated state 6104 command-select = "CLOSE" / "UNSELECT" / "EXPUNGE" / copy / 6105 move / fetch / store / search / uid 6106 ; Valid only when in Selected state 6108 continue-req = "+" SP (resp-text / base64) CRLF 6110 copy = "COPY" SP sequence-set SP mailbox 6112 create = "CREATE" SP mailbox 6113 ; Use of INBOX gives a NO error 6115 date = date-text / DQUOTE date-text DQUOTE 6117 date-day = 1*2DIGIT 6118 ; Day of month 6120 date-day-fixed = (SP DIGIT) / 2DIGIT 6121 ; Fixed-format version of date-day 6123 date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" / 6124 "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec" 6126 date-text = date-day "-" date-month "-" date-year 6128 date-year = 4DIGIT 6130 date-time = DQUOTE date-day-fixed "-" date-month "-" date-year 6131 SP time SP zone DQUOTE 6133 delete = "DELETE" SP mailbox 6134 ; Use of INBOX gives a NO error 6136 digit-nz = %x31-39 6137 ; 1-9 6139 eitem-standard-tag = atom 6140 ; a tag for LIST extended data item defined in a Standard 6141 ; Track or Experimental RFC. 6143 eitem-vendor-tag = vendor-token "-" atom 6144 ; a vendor-specific tag for LIST extended data item 6146 enable = "ENABLE" 1*(SP capability) 6148 enable-data = "ENABLED" *(SP capability) 6150 envelope = "(" env-date SP env-subject SP env-from SP 6151 env-sender SP env-reply-to SP env-to SP env-cc SP 6152 env-bcc SP env-in-reply-to SP env-message-id ")" 6154 env-bcc = "(" 1*address ")" / nil 6156 env-cc = "(" 1*address ")" / nil 6158 env-date = nstring 6160 env-from = "(" 1*address ")" / nil 6162 env-in-reply-to = nstring 6164 env-message-id = nstring 6166 env-reply-to = "(" 1*address ")" / nil 6168 env-sender = "(" 1*address ")" / nil 6170 env-subject = nstring 6172 env-to = "(" 1*address ")" / nil 6174 esearch-response = "ESEARCH" [search-correlator] [SP "UID"] 6175 *(SP search-return-data) 6176 ; ESEARCH response replaces SEARCH response 6177 ; from IMAP4rev1. 6179 examine = "EXAMINE" SP mailbox 6181 fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" / 6182 fetch-att / "(" fetch-att *(SP fetch-att) ")") 6184 fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" / 6185 "RFC822.SIZE" / 6186 "BODY" ["STRUCTURE"] / "UID" / 6187 "BODY" section [partial] / 6188 "BODY.PEEK" section [partial] / 6189 "BINARY" [".PEEK"] section-binary [partial] / 6190 "BINARY.SIZE" section-binary 6192 flag = "\Answered" / "\Flagged" / "\Deleted" / 6193 "\Seen" / "\Draft" / flag-keyword / flag-extension 6194 ; Does not include "\Recent" 6196 flag-extension = "\" atom 6197 ; Future expansion. Client implementations 6198 ; MUST accept flag-extension flags. Server 6199 ; implementations MUST NOT generate 6200 ; flag-extension flags except as defined by 6201 ; future standard or standards-track 6202 ; revisions of this specification. 6203 ; "\Recent" was defined in RFC 3501 6204 ; and is now deprecated. 6206 flag-fetch = flag 6208 flag-keyword = "$MDNSent" / "$Forwarded" / "$Junk" / 6209 "$NotJunk" / "$Phishing" / atom 6211 flag-list = "(" [flag *(SP flag)] ")" 6213 flag-perm = flag / "\*" 6215 greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF 6217 header-fld-name = astring 6219 header-list = "(" header-fld-name *(SP header-fld-name) ")" 6221 idle = "IDLE" CRLF "DONE" 6223 initial-resp = (base64 / "=") 6224 ; "initial response" defined in 6225 ; Section 5.1 of [RFC4422] 6227 list = "LIST" [SP list-select-opts] SP mailbox SP mbox-or-pat 6228 [SP list-return-opts] 6230 list-mailbox = 1*list-char / string 6232 list-char = ATOM-CHAR / list-wildcards / resp-specials 6234 list-return-opts = "RETURN" SP 6235 "(" [return-option *(SP return-option)] ")" 6236 ; list return options, e.g., CHILDREN 6238 list-select-base-opt = "SUBSCRIBED" / option-extension 6239 ; options that can be used by themselves 6241 list-select-base-opt-quoted = DQUOTE list-select-base-opt DQUOTE 6243 list-select-independent-opt = "REMOTE" / option-extension 6244 ; options that do not syntactically interact with 6245 ; other options 6247 list-select-mod-opt = "RECURSIVEMATCH" / option-extension 6248 ; options that require a list-select-base-opt 6249 ; to also be present 6251 list-select-opt = list-select-base-opt / list-select-independent-opt 6252 / list-select-mod-opt 6253 ; An option registration template is described in 6254 ; Section 9.3 of this document. 6256 list-select-opts = "(" [ 6257 (*(list-select-opt SP) list-select-base-opt 6258 *(SP list-select-opt)) 6259 / (list-select-independent-opt 6260 *(SP list-select-independent-opt)) 6261 ] ")" 6262 ; Any number of options may be in any order. 6263 ; If a list-select-mod-opt appears, then a 6264 ; list-select-base-opt must also appear. 6265 ; This allows these: 6266 ; () 6267 ; (REMOTE) 6268 ; (SUBSCRIBED) 6269 ; (SUBSCRIBED REMOTE) 6270 ; (SUBSCRIBED RECURSIVEMATCH) 6271 ; (SUBSCRIBED REMOTE RECURSIVEMATCH) 6272 ; But does NOT allow these: 6273 ; (RECURSIVEMATCH) 6274 ; (REMOTE RECURSIVEMATCH) 6276 list-wildcards = "%" / "*" 6278 literal = "{" number64 ["+"] "}" CRLF *CHAR8 6279 ; represents the number of CHAR8s. 6280 ; A non-synchronizing literal is distinguished from 6281 ; a synchronizing literal by presence of the "+" 6282 ; before the closing "}". 6283 ; Non synchronizing literals are not allowed when 6284 ; sent from server to the client. 6286 literal8 = "~{" number64 "}" CRLF *OCTET 6287 ; represents the number of OCTETs 6288 ; in the response string. 6290 login = "LOGIN" SP userid SP password 6292 mailbox = "INBOX" / astring 6293 ; INBOX is case-insensitive. All case variants of 6294 ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX 6295 ; not as an astring. An astring which consists of 6296 ; the case-insensitive sequence "I" "N" "B" "O" "X" 6297 ; is considered to be INBOX and not an astring. 6298 ; Refer to section 5.1 for further 6299 ; semantic details of mailbox names. 6301 mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list / 6302 esearch-response / 6303 "STATUS" SP mailbox SP "(" [status-att-list] ")" / 6304 number SP "EXISTS" / Namespace-Response 6306 mailbox-list = "(" [mbx-list-flags] ")" SP 6307 (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox 6308 [SP mbox-list-extended] 6309 ; This is the list information pointed to by the ABNF 6310 ; item "mailbox-data", which is defined in [IMAP4] 6312 mbox-list-extended = "(" [mbox-list-extended-item 6313 *(SP mbox-list-extended-item)] ")" 6315 mbox-list-extended-item = mbox-list-extended-item-tag SP 6316 tagged-ext-val 6318 mbox-list-extended-item-tag = astring 6319 ; The content MUST conform to either "eitem-vendor-tag" 6320 ; or "eitem-standard-tag" ABNF productions. 6322 mbox-or-pat = list-mailbox / patterns 6324 mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag 6325 *(SP mbx-list-oflag) / 6326 mbx-list-oflag *(SP mbx-list-oflag) 6328 mbx-list-oflag = "\Noinferiors" / child-mbox-flag / 6329 "\Subscribed" / "\Remote" / flag-extension 6330 ; Other flags; multiple possible per LIST response 6332 mbx-list-sflag = "\NonExistent" / "\Noselect" / "\Marked" / "\Unmarked" 6333 ; Selectability flags; only one per LIST response 6335 media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" / 6336 "FONT" / "MESSAGE" / "MODEL" / "VIDEO" ) DQUOTE) 6337 / string) 6338 SP media-subtype 6339 ; Defined in [MIME-IMT]. 6340 ; FONT defined in RFC 8081. 6342 media-message = DQUOTE "MESSAGE" DQUOTE SP 6343 DQUOTE ("RFC822" / "GLOBAL") DQUOTE 6344 ; Defined in [MIME-IMT] 6346 media-subtype = string 6347 ; Defined in [MIME-IMT] 6349 media-text = DQUOTE "TEXT" DQUOTE SP media-subtype 6350 ; Defined in [MIME-IMT] 6352 message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att)) 6354 move = "MOVE" SP sequence-set SP mailbox 6356 msg-att = "(" (msg-att-dynamic / msg-att-static) 6357 *(SP (msg-att-dynamic / msg-att-static)) ")" 6359 msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")" 6360 ; MAY change for a message 6362 msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time / 6363 "RFC822.SIZE" SP number64 / 6364 "BODY" ["STRUCTURE"] SP body / 6365 "BODY" section ["<" number ">"] SP nstring / 6366 "BINARY" section-binary SP (nstring / literal8) / 6367 "BINARY.SIZE" section-binary SP number / 6368 "UID" SP uniqueid 6369 ; MUST NOT change for a message 6371 name-component = 1*UTF8-CHAR 6372 ; MUST NOT contain ".", "/", "%", or "*" 6374 namespace = nil / "(" 1*namespace-descr ")" 6376 namespace-command = "NAMESPACE" 6378 namespace-descr = "(" string SP 6379 (DQUOTE QUOTED-CHAR DQUOTE / nil) 6380 [namespace-response-extensions] ")" 6382 namespace-response-extensions = *namespace-response-extension 6384 namespace-response-extension = SP string SP 6385 "(" string *(SP string) ")" 6387 namespace-response = "NAMESPACE" SP namespace 6388 SP namespace SP namespace 6389 ; The first Namespace is the Personal Namespace(s). 6390 ; The second Namespace is the Other Users' 6391 ; Namespace(s). 6392 ; The third Namespace is the Shared Namespace(s). 6394 nil = "NIL" 6396 nstring = string / nil 6398 number = 1*DIGIT 6399 ; Unsigned 32-bit integer 6400 ; (0 <= n < 4,294,967,296) 6402 number64 = 1*DIGIT 6403 ; Unsigned 63-bit integer 6404 ; (0 <= n <= 9,223,372,036,854,775,807) 6406 nz-number = digit-nz *DIGIT 6407 ; Non-zero unsigned 32-bit integer 6408 ; (0 < n < 4,294,967,296) 6410 nz-number64 = digit-nz *DIGIT 6411 ; Unsigned 63-bit integer 6412 ; (0 < n <= 9,223,372,036,854,775,807) 6414 oldname-extended-item = "OLDNAME" SP "(" mailbox ")" 6415 ; Extended data item (mbox-list-extended-item) 6416 ; returned in a LIST response when a mailbox is 6417 ; renamed or deleted. Also returned when 6418 ; the server canonicalized the provided mailbox 6419 ; name. 6420 ; Note 1: the OLDNAME tag can be returned 6421 ; with or without surrounding quotes, as per 6422 ; mbox-list-extended-item-tag production. 6424 option-extension = (option-standard-tag / option-vendor-tag) 6425 [SP option-value] 6427 option-standard-tag = atom 6428 ; an option defined in a Standards Track or 6429 ; Experimental RFC 6431 option-val-comp = astring / 6432 option-val-comp *(SP option-val-comp) / 6433 "(" option-val-comp ")" 6435 option-value = "(" option-val-comp ")" 6437 option-vendor-tag = vendor-token "-" atom 6438 ; a vendor-specific option, non-standard 6440 partial-range = number64 ["." nz-number64] 6441 ; Copied from RFC 5092 (IMAP URL) 6442 ; and updated to support 64bit sizes. 6444 partial = "<" number64 "." nz-number64 ">" 6445 ; Partial FETCH request. 0-based offset of 6446 ; the first octet, followed by the number of octets 6447 ; in the fragment. 6449 password = astring 6451 patterns = "(" list-mailbox ")" 6452 ; [RFC5258] supports multiple patterns, 6453 ; but this document only requires one 6454 ; to be supported. 6455 ; If the server is also implementing 6456 ; [RFC5258], "patterns" syntax from that 6457 ; document must be followed. 6459 quoted = DQUOTE *QUOTED-CHAR DQUOTE 6461 QUOTED-CHAR = / 6462 "\" quoted-specials / UTF8-2 / UTF8-3 / UTF8-4 6464 quoted-specials = DQUOTE / "\" 6466 rename = "RENAME" SP mailbox SP mailbox 6467 ; Use of INBOX as a destination gives a NO error 6469 response = *(continue-req / response-data) response-done 6471 response-data = "*" SP (resp-cond-state / resp-cond-bye / 6472 mailbox-data / message-data / capability-data / 6473 enable-data) CRLF 6475 response-done = response-tagged / response-fatal 6477 response-fatal = "*" SP resp-cond-bye CRLF 6478 ; Server closes connection immediately 6480 response-tagged = tag SP resp-cond-state CRLF 6482 resp-code-apnd = "APPENDUID" SP nz-number SP append-uid 6483 resp-code-copy = "COPYUID" SP nz-number SP uid-set SP uid-set 6485 resp-cond-auth = ("OK" / "PREAUTH") SP resp-text 6486 ; Authentication condition 6488 resp-cond-bye = "BYE" SP resp-text 6490 resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text 6491 ; Status condition 6493 resp-specials = "]" 6495 resp-text = ["[" resp-text-code "]" SP] [text] 6497 resp-text-code = "ALERT" / 6498 "BADCHARSET" [SP "(" charset *(SP charset) ")" ] / 6499 capability-data / "PARSE" / 6500 "PERMANENTFLAGS" SP 6501 "(" [flag-perm *(SP flag-perm)] ")" / 6502 "READ-ONLY" / "READ-WRITE" / "TRYCREATE" / 6503 "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number / 6504 resp-code-apnd / resp-code-copy / "UIDNOTSTICKY" / 6505 "UNAVAILABLE" / "AUTHENTICATIONFAILED" / 6506 "AUTHORIZATIONFAILED" / "EXPIRED" / 6507 "PRIVACYREQUIRED" / "CONTACTADMIN" / "NOPERM" / 6508 "INUSE" / "EXPUNGEISSUED" / "CORRUPTION" / 6509 "SERVERBUG" / "CLIENTBUG" / "CANNOT" / 6510 "LIMIT" / "OVERQUOTA" / "ALREADYEXISTS" / 6511 "NONEXISTENT" / "NOTSAVED" / "HASCHILDREN" / 6512 "CLOSED" / 6513 "UNKNOWN-CTE" / 6514 atom [SP 1*] 6516 return-option = "SUBSCRIBED" / "CHILDREN" / status-option / 6517 option-extension 6519 search = "SEARCH" [search-return-opts] 6520 SP search-program 6522 search-correlator = SP "(" "TAG" SP tag-string ")" 6524 search-key = "ALL" / "ANSWERED" / "BCC" SP astring / 6525 "BEFORE" SP date / "BODY" SP astring / 6526 "CC" SP astring / "DELETED" / "FLAGGED" / 6527 "FROM" SP astring / "KEYWORD" SP flag-keyword / 6528 "ON" SP date / "SEEN" / 6529 "SINCE" SP date / "SUBJECT" SP astring / 6530 "TEXT" SP astring / "TO" SP astring / 6531 "UNANSWERED" / "UNDELETED" / "UNFLAGGED" / 6532 "UNKEYWORD" SP flag-keyword / "UNSEEN" / 6533 ; Above this line were in [IMAP2] 6534 "DRAFT" / "HEADER" SP header-fld-name SP astring / 6535 "LARGER" SP number64 / "NOT" SP search-key / 6536 "OR" SP search-key SP search-key / 6537 "SENTBEFORE" SP date / "SENTON" SP date / 6538 "SENTSINCE" SP date / "SMALLER" SP number64 / 6539 "UID" SP sequence-set / "UNDRAFT" / sequence-set / 6540 "(" search-key *(SP search-key) ")" 6542 search-modifier-name = tagged-ext-label 6544 search-mod-params = tagged-ext-val 6545 ; This non-terminal shows recommended syntax 6546 ; for future extensions. 6548 search-program = ["CHARSET" SP charset SP] 6549 search-key *(SP search-key) 6550 ; CHARSET argument to SEARCH MUST be 6551 ; registered with IANA. 6553 search-ret-data-ext = search-modifier-name SP search-return-value 6554 ; Note that not every SEARCH return option 6555 ; is required to have the corresponding 6556 ; ESEARCH return data. 6558 search-return-data = "MIN" SP nz-number / 6559 "MAX" SP nz-number / 6560 "ALL" SP sequence-set / 6561 "COUNT" SP number / 6562 search-ret-data-ext 6563 ; All return data items conform to 6564 ; search-ret-data-ext syntax. 6565 ; Note that "$" marker is not allowed 6566 ; after the ALL return data item. 6568 search-return-opts = SP "RETURN" SP "(" [search-return-opt 6569 *(SP search-return-opt)] ")" 6571 search-return-opt = "MIN" / "MAX" / "ALL" / "COUNT" / 6572 "SAVE" / 6573 search-ret-opt-ext 6574 ; conforms to generic search-ret-opt-ext 6575 ; syntax 6577 search-ret-opt-ext = search-modifier-name [SP search-mod-params] 6578 search-return-value = tagged-ext-val 6579 ; Data for the returned search option. 6580 ; A single "nz-number"/"number"/"number64" value 6581 ; can be returned as an atom (i.e., without 6582 ; quoting). A sequence-set can be returned 6583 ; as an atom as well. 6585 section = "[" [section-spec] "]" 6587 section-binary = "[" [section-part] "]" 6589 section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list / 6590 "TEXT" 6591 ; top-level or MESSAGE/RFC822 or MESSAGE/GLOBAL part 6593 section-part = nz-number *("." nz-number) 6594 ; body part reference. 6595 ; Allows for accessing nested body parts. 6597 section-spec = section-msgtext / (section-part ["." section-text]) 6599 section-text = section-msgtext / "MIME" 6600 ; text other than actual body part (headers, etc.) 6602 select = "SELECT" SP mailbox 6604 seq-number = nz-number / "*" 6605 ; message sequence number (COPY, FETCH, STORE 6606 ; commands) or unique identifier (UID COPY, 6607 ; UID FETCH, UID STORE commands). 6608 ; * represents the largest number in use. In 6609 ; the case of message sequence numbers, it is 6610 ; the number of messages in a non-empty mailbox. 6611 ; In the case of unique identifiers, it is the 6612 ; unique identifier of the last message in the 6613 ; mailbox or, if the mailbox is empty, the 6614 ; mailbox's current UIDNEXT value. 6615 ; The server should respond with a tagged BAD 6616 ; response to a command that uses a message 6617 ; sequence number greater than the number of 6618 ; messages in the selected mailbox. This 6619 ; includes "*" if the selected mailbox is empty. 6621 seq-range = seq-number ":" seq-number 6622 ; two seq-number values and all values between 6623 ; these two regardless of order. 6624 ; Example: 2:4 and 4:2 are equivalent and indicate 6625 ; values 2, 3, and 4. 6627 ; Example: a unique identifier sequence range of 6628 ; 3291:* includes the UID of the last message in 6629 ; the mailbox, even if that value is less than 3291. 6631 sequence-set = (seq-number / seq-range) ["," sequence-set] 6632 ; set of seq-number values, regardless of order. 6633 ; Servers MAY coalesce overlaps and/or execute the 6634 ; sequence in any order. 6635 ; Example: a message sequence number set of 6636 ; 2,4:7,9,12:* for a mailbox with 15 messages is 6637 ; equivalent to 2,4,5,6,7,9,12,13,14,15 6638 ; Example: a message sequence number set of *:4,5:7 6639 ; for a mailbox with 10 messages is equivalent to 6640 ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and 6641 ; overlap coalesced to be 4,5,6,7,8,9,10. 6643 sequence-set =/ seq-last-command 6644 ; Allow for "result of the last command" indicator. 6646 seq-last-command = "$" 6648 status = "STATUS" SP mailbox SP 6649 "(" status-att *(SP status-att) ")" 6651 status-att = "MESSAGES" / "UIDNEXT" / "UIDVALIDITY" / 6652 "UNSEEN" / "DELETED" / "SIZE" 6654 status-att-val = ("MESSAGES" SP number) / 6655 ("UIDNEXT" SP nz-number) / 6656 ("UIDVALIDITY" SP nz-number) / 6657 ("UNSEEN" SP number) / 6658 ("DELETED" SP number) / 6659 ("SIZE" SP number64) 6660 ; Extensions to the STATUS responses 6661 ; should extend this production. 6662 ; Extensions should use the generic 6663 ; syntax defined by tagged-ext. 6665 status-att-list = status-att-val *(SP status-att-val) 6667 status-option = "STATUS" SP "(" status-att *(SP status-att) ")" 6668 ; This ABNF production complies with 6669 ; syntax. 6671 store = "STORE" SP sequence-set SP store-att-flags 6673 store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP 6674 (flag-list / (flag *(SP flag))) 6676 string = quoted / literal 6678 subscribe = "SUBSCRIBE" SP mailbox 6680 tag = 1* 6682 tag-string = astring 6683 ; represented as 6685 tagged-ext-label = tagged-label-fchar *tagged-label-char 6686 ; Is a valid RFC 3501 "atom". 6688 tagged-label-fchar = ALPHA / "-" / "_" / "." 6690 tagged-label-char = tagged-label-fchar / DIGIT / ":" 6692 tagged-ext-comp = astring / 6693 tagged-ext-comp *(SP tagged-ext-comp) / 6694 "(" tagged-ext-comp ")" 6695 ; Extensions that follow this general 6696 ; syntax should use nstring instead of 6697 ; astring when appropriate in the context 6698 ; of the extension. 6699 ; Note that a message set or a "number" 6700 ; can always be represented as an "atom". 6701 ; An URL should be represented as 6702 ; a "quoted" string. 6704 tagged-ext-simple = sequence-set / number / number64 6706 tagged-ext-val = tagged-ext-simple / 6707 "(" [tagged-ext-comp] ")" 6709 text = 1*(TEXT-CHAR / UTF8-2 / UTF8-3 / UTF8-4) 6710 ; Non ASCII text can only be returned 6711 ; after ENABLE IMAP4rev2 command 6713 TEXT-CHAR = 6715 time = 2DIGIT ":" 2DIGIT ":" 2DIGIT 6716 ; Hours minutes seconds 6718 uid = "UID" SP 6719 (copy / move / fetch / search / store / uid-expunge) 6720 ; Unique identifiers used instead of message 6721 ; sequence numbers 6723 uid-expunge = "EXPUNGE" SP sequence-set 6724 ; Unique identifiers used instead of message 6725 ; sequence numbers 6727 uid-set = (uniqueid / uid-range) *("," uid-set) 6729 uid-range = (uniqueid ":" uniqueid) 6730 ; two uniqueid values and all values 6731 ; between these two regards of order. 6732 ; Example: 2:4 and 4:2 are equivalent. 6734 uniqueid = nz-number 6735 ; Strictly ascending 6737 unsubscribe = "UNSUBSCRIBE" SP mailbox 6739 userid = astring 6741 UTF8-CHAR = 6743 UTF8-2 = 6745 UTF8-3 = 6747 UTF8-4 = 6749 vendor-token = "vendor." name-component 6750 ; Definition copied from RFC 2244. 6751 ; MUST be registered with IANA 6753 x-command = "X" atom 6755 zone = ("+" / "-") 4DIGIT 6756 ; Signed four-digit value of hhmm representing 6757 ; hours and minutes east of Greenwich (that is, 6758 ; the amount that the given time differs from 6759 ; Universal Time). Subtracting the timezone 6760 ; from the given time will give the UT form. 6761 ; The Universal Time zone is "+0000". 6763 10. Author's Note 6765 This document is a revision or rewrite of earlier documents, and 6766 supercedes the protocol specification in those documents: RFC 3501, 6767 RFC 2060, RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and 6768 RFC 1064. 6770 11. Security Considerations 6772 IMAP4rev2 protocol transactions, including electronic mail data, are 6773 sent in the clear over the network unless protection from snooping is 6774 negotiated. This can be accomplished either by the use of Implicit 6775 TLS port, STARTTLS command, negotiated privacy protection in the 6776 AUTHENTICATE command, or some other protection mechanism. 6778 11.1. TLS related Security Considerations 6780 This section applies to both use of STARTTLS command and Implicit TLS 6781 port. 6783 IMAP client and server implementations MUST comply with relevant TLS 6784 recommendations from [RFC8314]. 6786 Clients and servers MUST implement TLS 1.2 [TLS-1.2] or newer. Use 6787 of TLS 1.3 [TLS-1.3] is RECOMMENDED. TLS 1.2 may be used only in 6788 cases where the other party has not yet implemented TLS 1.3. 6789 Additionally, when using TLS 1.2, IMAP implementations MUST implement 6790 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 cipher suite. This is 6791 important as it assures that any two compliant implementations can be 6792 configured to interoperate. Other TLS cipher suites recommended in 6793 RFC 7525 are RECOMMENDED: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256, 6794 TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 and 6795 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384. All other cipher suites are 6796 OPTIONAL. Note that this is a change from section 2.1 of [IMAP-TLS]. 6798 The list of mandatory-to-implement TLS 1.3 cipher suites is described 6799 in Section 9.1 of [TLS-1.3]. 6801 During the TLS negotiation [TLS-1.3][TLS-1.2], the client MUST check 6802 its understanding of the server hostname against the server's 6803 identity as presented in the server Certificate message, in order to 6804 prevent man-in-the-middle attacks. This procedure is described in 6805 [RFC7817]. 6807 Both the client and server MUST check the result of the STARTTLS 6808 command and subsequent TLS ([TLS-1.3][TLS-1.2]) negotiation to see 6809 whether acceptable authentication and/or privacy was achieved. 6811 11.2. STARTTLS command versa use of Implicit TLS port 6813 For maximum backward compatibility clients MUST implement both TLS 6814 negotiation on implicit TLS port and TLS negotiation using STARTTLS 6815 command. 6817 Servers MUST implement TLS negotiation on implicit TLS port and 6818 SHOULD implement STARTTLS command on cleartext port. 6820 Some site/firewall maintainers insist on TLS site-wide and prefer not 6821 to rely on a configuration option in each higher-level protocol. For 6822 this reason, IMAP4rev2 clients SHOULD try both ports 993 and 143 (and 6823 both IPv4 and IPv6) concurrently by default, unless overriden by 6824 either user configuration or DNS SRV records [RFC6186]. Note that if 6825 a server answers on both ports, it MUST allow STARTTLS command on 6826 port 143. 6828 11.3. Client handling of unsolicited responses not suitable for the 6829 current connection state 6831 Cleartext mail transmission (whether caused by firewall configuration 6832 errors that result in TLS stripping or weak security policies in 6833 email clients that choose not to negotiate TLS in the first place) 6834 can enable injection of responses that can confuse or even cause 6835 crashes in email clients. The following measures are recommended to 6836 minimize damage from them. 6838 See Section 7.1.4 for special security considerations related to 6839 PREAUTH response. 6841 Many server responses and response codes are only meaningful in 6842 authenticated or even selected state. However, nothing prevents a 6843 server (or a man-in-the-middle attacker) from sending such invalid 6844 responses in cleartext before STARTTLS/AUTHENTICATE commands are 6845 issued. Before authentication clients SHOULD ignore any responses 6846 other than CAPABILITY and server status responses (Section 7.1), 6847 as well as any response codes other than CAPABILITY. Client 6848 SHOULD ignore the ALERT response code until after TLS has been 6849 successfully negotiated (whether using STARTTLS or TLS negotiation 6850 on implicit TLS port). Unless explicitly allowed by an IMAP 6851 extension, when not in selected state clients MUST ignore 6852 responses/response codes related to message and mailbox status 6853 such as FLAGS, EXIST, EXPUNGE and FETCH. 6855 11.4. COPYUID and APPENDUID response codes 6857 The COPYUID and APPENDUID response codes return information about the 6858 mailbox, which may be considered sensitive if the mailbox has 6859 permissions set that permit the client to COPY or APPEND to the 6860 mailbox, but not SELECT or EXAMINE it. 6862 Consequently, these response codes SHOULD NOT be issued if the client 6863 does not have access to SELECT or EXAMINE the mailbox. 6865 11.5. LIST command and Other Users' namespace 6867 In response to a LIST command containing an argument of the Other 6868 Users' Namespace prefix, a server SHOULD NOT list users that have not 6869 granted list access to their personal mailboxes to the currently 6870 authenticated user. Providing such a list, could compromise security 6871 by potentially disclosing confidential information of who is located 6872 on the server, or providing a starting point of a list of user 6873 accounts to attack. 6875 11.6. Other Security Considerations 6877 A server error message for an AUTHENTICATE command which fails due to 6878 invalid credentials SHOULD NOT detail why the credentials are 6879 invalid. 6881 Use of the LOGIN command sends passwords in the clear. This can be 6882 avoided by using the AUTHENTICATE command with a [SASL] mechanism 6883 that does not use plaintext passwords, by first negotiating 6884 encryption via STARTTLS or some other protection mechanism. 6886 A server implementation MUST implement a configuration that, at the 6887 time of authentication, requires: 6888 (1) The STARTTLS command has been negotiated or TLS negotiated on 6889 implicit TLS port. 6890 OR 6891 (2) Some other mechanism that protects the session from password 6892 snooping has been provided. 6893 OR 6894 (3) The following measures are in place: 6895 (a) The LOGINDISABLED capability is advertised, and [SASL] mechanisms 6896 (such as PLAIN) using plaintext passwords are NOT advertised in the 6897 CAPABILITY list. 6898 AND 6899 (b) The LOGIN command returns an error even if the password is 6900 correct. 6901 AND 6902 (c) The AUTHENTICATE command returns an error with all [SASL] 6903 mechanisms that use plaintext passwords, even if the password is 6904 correct. 6906 A server error message for a failing LOGIN command SHOULD NOT specify 6907 that the user name, as opposed to the password, is invalid. 6909 A server SHOULD have mechanisms in place to limit or delay failed 6910 AUTHENTICATE/LOGIN attempts. 6912 A server SHOULD report any authentication failure and analyze such 6913 authentication failure attempt with regard to a password brute force 6914 attack as well as a password spraying attack. Accounts that match 6915 password spraying attacks MUST be blocked and request to change their 6916 passwords and only password with significant strength SHOULD be 6917 accepted. 6919 Additional security considerations are discussed in the section 6920 discussing the AUTHENTICATE (see Section 6.2.2) and LOGIN (see 6921 Section 6.2.3) commands. 6923 12. IANA Considerations 6925 IANA is requested to update "Service Names and Transport Protocol 6926 Port Numbers" registry as follows: 6928 1. Registration for TCP port 143 and the corresponding "imap" 6929 service name should be updated to point to this document and RFC 6930 3501. 6932 2. Registration for TCP port 993 and the corresponding "imaps" 6933 service name should be updated to point to this document, RFC 6934 8314 and RFC 3501. 6936 3. Both UDP port 143 and UDP port 993 should be marked as "Reserved" 6937 in the registry. 6939 Additional IANA actions are specified in subsection of this section. 6941 12.1. Updates to IMAP4 Capabilities registry 6943 IMAP4 capabilities are registered by publishing a standards track or 6944 IESG approved informational or experimental RFC. The registry is 6945 currently located at: https://www.iana.org/assignments/ 6946 imap4-capabilities 6948 As this specification revises the AUTH= prefix, STARTTLS and 6949 LOGINDISABLED extensions, IANA is requested to update registry 6950 entries for these 3 extensions to point to this document and RFC 6951 3501. 6953 12.2. GSSAPI/SASL service name 6955 GSSAPI/Kerberos/SASL service names are registered by publishing a 6956 standards track or IESG approved experimental RFC. The registry is 6957 currently located at: https://www.iana.org/assignments/gssapi- 6958 service-names 6959 IANA is requested to update the "imap" service name previously 6960 registered in RFC 3501, to point to both this document and RFC 3501. 6962 12.3. LIST Selection Options, LIST Return Options, LIST extended data 6963 items 6965 [RFC5258] specifies IANA registration procedures for LIST Selection 6966 Options, LIST Return Options, LIST extended data items. This 6967 document doesn't change these registration procedures. In particular 6968 LIST selection options (Section 6.3.9.1) and LIST return options 6969 (Section 6.3.9.2) are registered using the procedure specified in 6970 Section 9 of [RFC5258] (and using the registration template from 6971 Section 9.3 of [RFC5258]). LIST Extended Data Items are registered 6972 using the registration template from Section 9.6 of [RFC5258]). 6974 IANA is requested to add a reference to [RFCXXXX] for the "OLDNAME" 6975 LIST-EXTENDED extended data item entry. This is in addition to the 6976 existing reference to [RFC5465]. 6978 12.4. IMAP Mailbox Name Attributes and IMAP Response Codes 6980 IANA is requested to update the "IMAP Mailbox Name Attributes" 6981 registry to point to this document in addition to RFC 3501. 6983 IANA is requested to update the "IMAP Response Codes" registry to 6984 point to this document in addition to RFC 3501. 6986 13. References 6988 13.1. Normative References 6990 [RFC4752] Melnikov, A., Ed., "The Kerberos V5 ("GSSAPI") Simple 6991 Authentication and Security Layer (SASL) Mechanism", 6992 RFC 4752, DOI 10.17487/RFC4752, November 2006, 6993 . 6995 [RFC5258] Leiba, B. and A. Melnikov, "Internet Message Access 6996 Protocol version 4 - LIST Command Extensions", RFC 5258, 6997 DOI 10.17487/RFC5258, June 2008, 6998 . 7000 [RFC5788] Melnikov, A. and D. Cridland, "IMAP4 Keyword Registry", 7001 RFC 5788, DOI 10.17487/RFC5788, March 2010, 7002 . 7004 [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 7005 Specifications: ABNF", STD 68, RFC 5234, January 2008, 7006 . 7008 [ANONYMOUS] 7009 Zeilenga, K., "Anonymous Simple Authentication and 7010 Security Layer (SASL) Mechanism", RFC 4505, June 2006, 7011 . 7013 [CHARSET] Freed, N. and J. Postel, "IANA Charset Registration 7014 Procedures", BCP 19, RFC 2978, October 2000, 7015 . 7017 [SCRAM-SHA-256] 7018 Hansen, T., "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS Simple 7019 Authentication and Security Layer (SASL) Mechanisms", 7020 RFC 7677, DOI 10.17487/RFC7677, November 2015, 7021 . 7023 [DISPOSITION] 7024 Troost, R., Dorner, S., and K. Moore, Ed., "Communicating 7025 Presentation Information in Internet Messages: The 7026 Content-Disposition Header Field", RFC 2183, August 1997, 7027 . 7029 [PLAIN] Zeilenga, K., Ed., "The PLAIN Simple Authentication and 7030 Security Layer (SASL) Mechanism", RFC 4616, August 2006, 7031 . 7033 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 7034 Requirement Levels", BCP 14, RFC 2119, 7035 DOI 10.17487/RFC2119, March 1997, 7036 . 7038 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 7039 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 7040 May 2017, . 7042 [LANGUAGE-TAGS] 7043 Alvestrand, H., "Content Language Headers", RFC 3282, May 7044 2002, . 7046 [LOCATION] 7047 Palme, J., Hopmann, A., and N. Shelness, "MIME 7048 Encapsulation of Aggregate Documents, such as HTML 7049 (MHTML)", RFC 2557, March 1999, 7050 . 7052 [MD5] Myers, J. and M. Rose, "The Content-MD5 Header Field", 7053 RFC 1864, October 1995, 7054 . 7056 [MIME-HDRS] 7057 Moore, K., "MIME (Multipurpose Internet Mail Extensions) 7058 Part Three: Message Header Extensions for Non-ASCII Text", 7059 RFC 2047, November 1996, 7060 . 7062 [MIME-IMB] 7063 Freed, N. and N. Borenstein, "Multipurpose Internet Mail 7064 Extensions (MIME) Part One: Format of Internet Message 7065 Bodies", RFC 2045, November 1996, 7066 . 7068 [MIME-IMT] 7069 Freed, N. and N. Borenstein, "Multipurpose Internet Mail 7070 Extensions (MIME) Part Two: Media Types", RFC 2046, 7071 November 1996, . 7073 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 7074 Word Extensions: Character Sets, Languages, and 7075 Continuations", RFC 2231, DOI 10.17487/RFC2231, November 7076 1997, . 7078 [RFC-5322] 7079 Resnick, P., Ed., "Internet Message Format", RFC 5322, 7080 October 2008, . 7082 [SASL] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple 7083 Authentication and Security Layer (SASL)", RFC 4422, June 7084 2006, . 7086 [TLS-1.2] Dierks, T. and E. Rescorla, "The Transport Layer Security 7087 (TLS) Protocol Version 1.2", RFC 5246, August 2008, 7088 . 7090 [TLS-1.3] Rescorla, E., "The Transport Layer Security (TLS) Protocol 7091 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 7092 . 7094 [UTF-7] Goldsmith, D. and M. Davis, "UTF-7 A Mail-Safe 7095 Transformation Format of Unicode", RFC 2152, May 1997, 7096 . 7098 [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 7099 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 7100 2003, . 7102 [MULTIAPPEND] 7103 Crispin, M., "Internet Message Access Protocol (IMAP) - 7104 MULTIAPPEND Extension", RFC 3502, March 2003, 7105 . 7107 [NET-UNICODE] 7108 Klensin, J. and M. Padlipsky, "Unicode Format for Network 7109 Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, 7110 . 7112 [I18N-HDRS] 7113 Yang, A., Steele, S., and N. Freed, "Internationalized 7114 Email Headers", RFC 6532, DOI 10.17487/RFC6532, February 7115 2012, . 7117 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 7118 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 7119 . 7121 [RFC7817] Melnikov, A., "Updated Transport Layer Security (TLS) 7122 Server Identity Check Procedure for Email-Related 7123 Protocols", RFC 7817, DOI 10.17487/RFC7817, March 2016, 7124 . 7126 [RFC8098] Hansen, T., Ed. and A. Melnikov, Ed., "Message Disposition 7127 Notification", STD 85, RFC 8098, DOI 10.17487/RFC8098, 7128 February 2017, . 7130 [RFC8314] Moore, K. and C. Newman, "Cleartext Considered Obsolete: 7131 Use of Transport Layer Security (TLS) for Email Submission 7132 and Access", RFC 8314, DOI 10.17487/RFC8314, January 2018, 7133 . 7135 [IMAP-IMPLEMENTATION] 7136 Leiba, B., "IMAP4 Implementation Recommendations", 7137 RFC 2683, September 1999, 7138 . 7140 [IMAP-MULTIACCESS] 7141 Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", 7142 RFC 2180, July 1997, 7143 . 7145 13.2. Informative References (related protocols) 7147 [CERT-555316] 7148 CERT, "Vulnerability Note VU#555316: STARTTLS plaintext 7149 command injection vulnerability", September 2011, 7150 . 7152 [RFC2193] Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193, 7153 DOI 10.17487/RFC2193, September 1997, 7154 . 7156 [RFC3348] Gahrns, M. and R. Cheng, "The Internet Message Action 7157 Protocol (IMAP4) Child Mailbox Extension", RFC 3348, 7158 DOI 10.17487/RFC3348, July 2002, 7159 . 7161 [RFC3503] Melnikov, A., "Message Disposition Notification (MDN) 7162 profile for Internet Message Access Protocol (IMAP)", 7163 RFC 3503, DOI 10.17487/RFC3503, March 2003, 7164 . 7166 [RFC5256] Crispin, M. and K. Murchison, "Internet Message Access 7167 Protocol - SORT and THREAD Extensions", RFC 5256, 7168 DOI 10.17487/RFC5256, June 2008, 7169 . 7171 [RFC5465] Gulbrandsen, A., King, C., and A. Melnikov, "The IMAP 7172 NOTIFY Extension", RFC 5465, DOI 10.17487/RFC5465, 7173 February 2009, . 7175 [RFC6186] Daboo, C., "Use of SRV Records for Locating Email 7176 Submission/Access Services", RFC 6186, 7177 DOI 10.17487/RFC6186, March 2011, 7178 . 7180 [RFC7888] Melnikov, A., Ed., "IMAP4 Non-synchronizing Literals", 7181 RFC 7888, DOI 10.17487/RFC7888, May 2016, 7182 . 7184 [IMAP-DISC] 7185 Melnikov, A., Ed., "Synchronization Operations for 7186 Disconnected IMAP4 Clients", RFC 4549, June 2006, 7187 . 7189 [IMAP-I18N] 7190 Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet 7191 Message Access Protocol Internationalization", RFC 5255, 7192 DOI 10.17487/RFC5255, June 2008, 7193 . 7195 [IMAP-MODEL] 7196 Crispin, M., "Distributed Electronic Mail Models in 7197 IMAP4", RFC 1733, December 1994, 7198 . 7200 [IMAP-UTF-8] 7201 Resnick, P., Ed., Newman, C., Ed., and S. Shen, Ed., "IMAP 7202 Support for UTF-8", RFC 6855, DOI 10.17487/RFC6855, March 7203 2013, . 7205 [SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, 7206 October 2008, . 7208 [RFC3516] Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516, 7209 DOI 10.17487/RFC3516, April 2003, 7210 . 7212 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 7213 RFC 4314, December 2005, 7214 . 7216 [RFC2087] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January 7217 1997, . 7219 [IMAP-URL] 7220 Melnikov, A., Ed. and C. Newman, "IMAP URL Scheme", 7221 RFC 5092, DOI 10.17487/RFC5092, November 2007, 7222 . 7224 [IMAP-KEYWORDS-REG] 7225 IANA, "IMAP and JMAP Keywords", December 2009, 7226 . 7229 [IMAP-MAILBOX-NAME-ATTRS-REG] 7230 IANA, "IMAP Mailbox Name Attributes", June 2018, 7231 . 7234 [CHARSET-REG] 7235 IANA, "Character Set Registrations", May 2015, 7236 . 7239 13.3. Informative References (historical aspects of IMAP and related 7240 protocols) 7242 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 7243 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 7244 . 7246 [IMAP-COMPAT] 7247 Crispin, M., "IMAP4 Compatibility with IMAP2bis", 7248 RFC 2061, December 1996, 7249 . 7251 [IMAP-HISTORICAL] 7252 Crispin, M., "IMAP4 Compatibility with IMAP2 and 7253 IMAP2bis", RFC 1732, December 1994, 7254 . 7256 [IMAP-OBSOLETE] 7257 Crispin, M., "Internet Message Access Protocol - Obsolete 7258 Syntax", RFC 2062, December 1996, 7259 . 7261 [IMAP2] Crispin, M., "Interactive Mail Access Protocol: Version 7262 2", RFC 1176, August 1990, 7263 . 7265 [RFC-822] Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET 7266 TEXT MESSAGES", STD 11, RFC 822, August 1982, 7267 . 7269 [IMAP-TLS] 7270 Newman, C., "Using TLS with IMAP, POP3 and ACAP", 7271 RFC 2595, June 1999, 7272 . 7274 Appendix A. Backward compatibility with IMAP4rev1 7276 An implementation that wants to remain compatible with IMAP4rev1 can 7277 advertise both IMAP4rev1 and IMAP4rev2 in its CAPABILITY response/ 7278 response code. While some IMAP4rev1 responses were removed in 7279 IMAP4rev2, their presence will not break IMAP4rev2-only clients. 7281 If both IMAP4rev1 and IMAP4rev2 are advertised, an IMAP client that 7282 wants to use IMAP4rev2 MUST issue an "ENABLE IMAP4rev2" command. 7284 Servers advertising both IMAP4rev1 and IMAP4rev2 MUST NOT generate 7285 UTF-8 quoted strings unless the client has issued "ENABLE IMAP4rev2". 7287 Consider implementation of mechanisms described or referenced in 7288 [IMAP-UTF-8] to achieve this goal. 7290 Servers advertising both IMAP4rev1 and IMAP4rev2, and clients 7291 intending to be compatible with IMAP4rev1 servers MUST be compatible 7292 with the international mailbox naming convention described in the 7293 following subsection. 7295 Also see Appendix D for special considerations for servers that 7296 support 63 bit body part/message sizes and want to advertise support 7297 for both IMAP4rev1 and IMAP4rev2. 7299 A.1. Mailbox International Naming Convention for compatibility with 7300 IMAP4rev1 7302 Support for the Mailbox International Naming Convention described in 7303 this section is not required for IMAP4rev2-only clients and servers. 7304 It is only used for backward compatibility with IMAP4rev1 7305 implementations. 7307 By convention, international mailbox names in IMAP4rev1 are specified 7308 using a modified version of the UTF-7 encoding described in [UTF-7]. 7309 Modified UTF-7 may also be usable in servers that implement an 7310 earlier version of this protocol. 7312 In modified UTF-7, printable US-ASCII characters, except for "&", 7313 represent themselves; that is, characters with octet values 0x20-0x25 7314 and 0x27-0x7e. The character "&" (0x26) is represented by the two- 7315 octet sequence "&-". 7317 All other characters (octet values 0x00-0x1f and 0x7f-0xff) are 7318 represented in modified BASE64, with a further modification from 7319 [UTF-7] that "," is used instead of "/". Modified BASE64 MUST NOT be 7320 used to represent any printing US-ASCII character which can represent 7321 itself. Only characters inside the modified BASE64 alphabet are 7322 permitted in modified BASE64 text. 7324 "&" is used to shift to modified BASE64 and "-" to shift back to US- 7325 ASCII. There is no implicit shift from BASE64 to US-ASCII, and null 7326 shifts ("-&" while in BASE64; note that "&-" while in US-ASCII means 7327 "&") are not permitted. However, all names start in US-ASCII, and 7328 MUST end in US-ASCII; that is, a name that ends with a non-ASCII 7329 ISO-10646 character MUST end with a "-"). 7331 The purpose of these modifications is to correct the following 7332 problems with UTF-7: 7334 1. UTF-7 uses the "+" character for shifting; this conflicts with 7335 the common use of "+" in mailbox names, in particular USENET 7336 newsgroup names. 7338 2. UTF-7's encoding is BASE64 which uses the "/" character; this 7339 conflicts with the use of "/" as a popular hierarchy delimiter. 7341 3. UTF-7 prohibits the unencoded usage of "\"; this conflicts with 7342 the use of "\" as a popular hierarchy delimiter. 7344 4. UTF-7 prohibits the unencoded usage of "~"; this conflicts with 7345 the use of "~" in some servers as a home directory indicator. 7347 5. UTF-7 permits multiple alternate forms to represent the same 7348 string; in particular, printable US-ASCII characters can be 7349 represented in encoded form. 7351 Although modified UTF-7 is a convention, it establishes certain 7352 requirements on server handling of any mailbox name with an embedded 7353 "&" character. In particular, server implementations MUST preserve 7354 the exact form of the modified BASE64 portion of a modified UTF-7 7355 name and treat that text as case-sensitive, even if names are 7356 otherwise case-insensitive or case-folded. 7358 Server implementations SHOULD verify that any mailbox name with an 7359 embedded "&" character, used as an argument to CREATE, is: in the 7360 correctly modified UTF-7 syntax, has no superfluous shifts, and has 7361 no encoding in modified BASE64 of any printing US-ASCII character 7362 which can represent itself. However, client implementations MUST NOT 7363 depend upon the server doing this, and SHOULD NOT attempt to create a 7364 mailbox name with an embedded "&" character unless it complies with 7365 the modified UTF-7 syntax. 7367 Server implementations which export a mail store that does not follow 7368 the modified UTF-7 convention MUST convert to modified UTF-7 any 7369 mailbox name that contains either non-ASCII characters or the "&" 7370 character. 7372 For example, here is a mailbox name which mixes English, Chinese, 7373 and Japanese text: ~peter/mail/&U,BTFw-/&ZeVnLIqe- 7375 For example, the string "&Jjo!" is not a valid mailbox name 7376 because it does not contain a shift to US-ASCII before the "!". 7377 The correct form is "&Jjo-!". The string "&U,BTFw-&ZeVnLIqe-" is 7378 not permitted because it contains a superfluous shift. The 7379 correct form is "&U,BTF2XlZyyKng-". 7381 Appendix B. Backward compatibility with BINARY extension 7383 IMAP4rev2 incorporates subset of functionality provided by the BINARY 7384 extension [RFC3516], in particular it includes additional FETCH items 7385 (BINARY, BINARY.PEEK and BINARY.SIZE), but not extensions to the 7386 APPEND command. IMAP4rev2 implementations that supports full RFC 7387 3516 functionality need to also advertise the BINARY capability in 7388 the CAPABILITY response/response code. 7390 Appendix C. Backward compatibility with LIST-EXTENDED extension 7392 IMAP4rev2 incorporates most of functionality provided by the LIST- 7393 EXTENDED extension [RFC5258]. In particular, multiple mailbox 7394 patterns syntax is not supported in IMAP4rev2, unless LIST-EXTENDED 7395 capability is also advertised in the CAPABILITY response/response 7396 code. 7398 Appendix D. 63 bit body part and message sizes 7400 IMAP4rev2 increases allowed body part and message sizes that servers 7401 can support from 32 to 63 bits. Server implementations don't have to 7402 support 63 bit long body parts/message sizes, however client 7403 implementations have to expect them. 7405 As IMAP4rev1 didn't support 63 bit long body part/message sizes, 7406 there is an interoperability issue exposed by 63 bit capable servers 7407 that are accessible by both IMAP4rev1 and IMAP4rev2 email clients. 7408 As IMAP4rev1 would be unable to retrieve full content of messages 7409 bigger than 4Gb, such servers either need to replace messages bigger 7410 that 4Gb with messages under 4Gb or hide them from IMAP4rev1 clients. 7411 This document doesn't prescribe any implementation strategy to 7412 address this issue. 7414 Appendix E. Changes from RFC 3501 / IMAP4rev1 7416 Below is the summary of changes since RFC 3501: 7418 1. Support for 64bit message and body part sizes. 7420 2. Folded in IMAP NAMESPACE (RFC 2342), UNSELECT (RFC 3691), 7421 UIDPLUS (RFC 4315), ESEARCH (RFC 4731), SEARCHRES (RFC 5182), 7422 ENABLE (RFC 5161), IDLE (RFC 2177), SASL-IR (RFC 4959), LIST- 7423 EXTENDED (RFC 5258), LIST-STATUS (RFC 5819), MOVE (RFC 6851) and 7424 LITERAL- (RFC 7888) extensions. Also folded RFC 4466 (IMAP ABNF 7425 extensions), RFC 5530 (response codes), the FETCH side of the 7426 BINARY extension (RFC 3516) and the list of new mailbox 7427 attributes from SPECIAL-USE (RFC 6154). 7429 3. Added STATUS SIZE (RFC 8438) and STATUS DELETED. 7431 4. SEARCH command now requires to return ESEARCH response (SEARCH 7432 response is now deprecated). 7434 5. Clarified which SEARCH keys have to use substring match and 7435 which don't. 7437 6. Clarified that server should decode parameter value 7438 continuations as described in [RFC2231]. This requirement was 7439 hidden in RFC 2231 itself. 7441 7. Clarified that COPYUID response code is returned for both MOVE 7442 and UID MOVE. 7444 8. Tighen requirements about COPY/MOVE commands not creating target 7445 mailbox. Also require them to return TRYCREATE response code, 7446 if the target mailbox doesn't exist and can be created. 7448 9. Added CLOSED response code from RFC 7162. SELECT/EXAMINE when a 7449 mailbox is already selected now requires a CLOSED response code 7450 to be returned. 7452 10. SELECT/EXAMINE are now required to return untagged LIST 7453 response. 7455 11. UNSEEN response code on SELECT/EXAMINE is now deprecated. 7457 12. RECENT response on SELECT/EXAMINE, \Recent flag, RECENT STATUS, 7458 SEARCH NEW items are now deprecated. 7460 13. Clarified that the server doesn't need to send a new 7461 PERMANENTFLAGS response code when a new keyword was successfully 7462 added and the server advertised \* earlier for the same mailbox. 7464 14. For future extensibility extended ABNF for tagged-ext-simple to 7465 allow for bare number64. 7467 15. Added SHOULD level requirement on IMAP servers to support 7468 $MDNSent, $Forwarded, $Junk, $NonJunk and $Phishing keywords. 7470 16. Mailbox names and message headers now allow for UTF-8. Support 7471 for Modified UTF-7 in mailbox names is not required, unless 7472 compatibility with IMAP4rev1 is desired. 7474 17. Removed the CHECK command. Clients should use NOOP instead. 7476 18. RFC822, RFC822.HEADER and RFC822.TEXT FETCH data items were 7477 deprecated. Clients should use the corresponding BODY[] 7478 variants instead. 7480 19. LSUB command was deprecated. Clients should use LIST 7481 (SUBSCRIBED) instead. 7483 20. IDLE command can now return updates not related to the currently 7484 selected mailbox state. 7486 21. All unsolicited FETCH updates are required to include UID. 7488 22. Clarified that client implementations MUST ignore response codes 7489 that they do not recognize. (Change from a SHOULD to a MUST.) 7491 23. resp-text ABNF non terminal was updated to allow for empty text. 7493 24. After ENABLE IMAP4rev2 human readable response text can include 7494 non ASCII encoded in UTF-8. 7496 25. Updated to use modern TLS-related recommendations as per RFC 7497 8314, RFC 7817, RFC 7525. 7499 26. Added warnings about use of ALERT response codes and PREAUTH 7500 response. 7502 27. Replaced DIGEST-MD5 SASL mechanism with SCRAM-SHA-256. DIGEST- 7503 MD5 was deprecated. 7505 28. Clarified that any command received from the client resets 7506 server autologout timer. 7508 29. Revised IANA registration procedure for IMAP extensions and 7509 removed "X" convention. 7511 30. Loosened requirements on servers when closing connections to be 7512 more aligned with existing practices. 7514 Appendix F. Other Recommended IMAP Extensions 7516 Support for the following extensions is recommended for all IMAP 7517 client and servers. While they significantly reduce bandwidth and/or 7518 number of round trips used by IMAP in certain situations, the EXTRA 7519 WG decided that requiring them as a part of IMAP4rev2 would push the 7520 bar to implement too high for new implementations. Also note that 7521 absence of any IMAP extension from this list doesn't make it somehow 7522 deficient or not recommended for use with IMAP4rev2. 7524 1. QRESYNC and CONDSTORE extensions (RFC 7162). They make 7525 discovering changes to IMAP mailboxes more efficient, at the 7526 expense of storing a bit more state. 7528 2. OBJECTID extension (RFC 8474) helps with preserving IMAP client 7529 cache when messages moved/copied or mailboxes are renamed. 7531 Appendix G. Acknowledgement 7533 Earlier versions of this document were edited by Mark Crispin. 7534 Sadly, he is no longer available to help with this work. Editors of 7535 this revisions are hoping that Mark would have approved. 7537 Chris Newman has contributed text on I18N and use of UTF-8 in 7538 messages and mailbox names. 7540 Thank you to Tony Hansen for helping with the index generation. 7541 Thank you to Murray Kucherawy, Timo Sirainen, Bron Gondwana, Stephan 7542 Bosch, Robert Sparks, Arnt Gulbrandsen and Daniel Migault for 7543 extensive feedback. 7545 This document incorporates text from RFC 4315 (by Mark Crispin), RFC 7546 4466 (by Cyrus Daboo), RFC 4731 (by Dave Cridland), RFC 5161 (by Arnt 7547 Gulbrandsen), RFC 5465 (by Arnt Gulbrandsen and Curtis King), RFC 7548 5530 (by Arnt Gulbrandsen), RFC 5819 (by Timo Sirainen), RFC 6154 (by 7549 Jamie Nicolson), RFC 8438 (by Stephan Bosch) so work done by authors/ 7550 editors of these documents is appreciated. Note that editors of this 7551 document were redacted from the above list. 7553 The CHILDREN return option was originally proposed by Mike Gahrns and 7554 Raymond Cheng in [RFC3348]. Most of the information in 7555 Section 6.3.9.5 is taken directly from their original specification 7556 [RFC3348]. 7558 Thank you to Damian Poddebniak, Fabian Ising, Hanno Boeck and 7559 Sebastian Schinzel for pointing out that the ENABLE command should be 7560 a member of "command-auth" and not "command-any" ABNF production, as 7561 well as pointing out security issues associated with ALERT, PREAUTH 7562 and other responses received before authentication. 7564 Index 7566 $ 7567 $Forwarded (predefined flag) 12 7568 $Junk (predefined flag) 13 7569 $MDNSent (predefined flag) 13 7570 $NotJunk (predefined flag) 13 7571 $Phishing (predefined flag) 13 7573 + 7574 +FLAGS 93 7575 +FLAGS.SILENT 93 7577 - 7578 -FLAGS 93 7579 -FLAGS.SILENT 93 7581 A 7582 ALERT (response code) 101 7583 ALL (fetch item) 89 7584 ALL (search key) 79 7585 ALL (search result option) 77 7586 ALREADYEXISTS (response code) 101 7587 ANSWERED (search key) 79 7588 APPEND (command) 69 7589 APPENDUID (response code) 101 7590 AUTHENTICATE (command) 30 7591 AUTHENTICATIONFAILED (response code) 102 7592 AUTHORIZATIONFAILED (response code) 102 7594 B 7595 BAD (response) 109 7596 BADCHARSET (response code) 102 7597 BCC (search key) 79 7598 BEFORE (search key) 79 7599 BINARY.PEEK[]<> (fetch item) 89 7600 BINARY.SIZE[] (fetch item) 90 7601 BINARY.SIZE[] (fetch result) 120 7602 BINARY[]<> (fetch result) 119 7603 BINARY[]<> (fetch item) 89 7604 BODY (fetch item) 90 7605 BODY (fetch result) 120 7606 BODY (search key) 79 7607 BODY.PEEK[
]<> (fetch item) 90 7608 BODYSTRUCTURE (fetch item) 91 7609 BODYSTRUCTURE (fetch result) 121 7610 BODY[
]<> (fetch result) 120 7611 BODY[
]<> (fetch item) 90 7612 BYE (response) 110 7613 Body Structure (message attribute) 14 7615 C 7616 CANNOT (response code) 102 7617 CAPABILITY (command) 26 7618 CAPABILITY (response code) 103 7619 CAPABILITY (response) 111 7620 CC (search key) 79 7621 CLIENTBUG (response code) 103 7622 CLOSE (command) 75 7623 CLOSED (response code) 103 7624 CONTACTADMIN (response code) 103 7625 COPY (command) 94 7626 COPYUID (response code) 103 7627 CORRUPTION (response code) 104 7628 COUNT (search result option) 77 7629 CREATE (command) 39 7631 D 7632 DELETE (command) 40 7633 DELETED (search key) 79 7634 DELETED (status item) 69 7635 DRAFT (search key) 79 7637 E 7638 ENABLE (command) 34 7639 ENVELOPE (fetch item) 91 7640 ENVELOPE (fetch result) 123 7641 ESEARCH (response) 117 7642 EXAMINE (command) 38 7643 EXPIRED (response code) 104 7644 EXPUNGE (command) 76 7645 EXPUNGE (response) 118 7646 EXPUNGEISSUED (response code) 104 7647 Envelope Structure (message attribute) 14 7649 F 7650 FAST (fetch item) 89 7651 FETCH (command) 88 7652 FETCH (response) 119 7653 FLAGGED (search key) 79 7654 FLAGS (fetch item) 91 7655 FLAGS (fetch result) 125 7656 FLAGS (response) 117 7657 FLAGS (store command data item) 93 7658 FLAGS.SILENT (store command data item) 93 7659 FROM (search key) 79 7660 FULL (fetch item) 89 7661 Flags (message attribute) 12 7663 H 7664 HASCHILDREN (response code) 105 7665 HEADER (part specifier) 91 7666 HEADER (search key) 80 7667 HEADER.FIELDS (part specifier) 91 7668 HEADER.FIELDS.NOT (part specifier) 91 7670 I 7671 IDLE (command) 72 7672 INTERNALDATE (fetch item) 91 7673 INTERNALDATE (fetch result) 125 7674 INUSE (response code) 105 7675 Internal Date (message attribute) 14 7677 K 7678 KEYWORD (search key) 80 7679 Keyword (type of flag) 12 7681 L 7682 LARGER (search key) 80 7683 LIMIT (response code) 105 7684 LIST (command) 45 7685 LIST (response) 112 7686 LOGOUT (command) 27 7688 M 7689 MAX (search result option) 77 7690 MAY (specification requirement term) 5 7691 MESSAGES (status item) 69 7692 MIME (part specifier) 92 7693 MIN (search result option) 77 7694 MOVE (command) 95 7695 MUST (specification requirement term) 5 7696 MUST NOT (specification requirement term) 5 7697 Message Sequence Number (message attribute) 11 7699 N 7700 NAMESPACE (command) 64 7701 NAMESPACE (response) 116 7702 NO (response) 109 7703 NONEXISTENT (response code) 105 7704 NOOP (command) 27 7705 NOPERM (response code) 105 7706 NOT (search key) 80 7707 NOT RECOMMENDED (specification requirement term) 5 7709 O 7710 OK (response) 108 7711 ON (search key) 80 7712 OPTIONAL (specification requirement term) 5 7713 OR (search key) 80 7714 OVERQUOTA (response code) 106 7716 P 7717 PARSE (response code) 106 7718 PERMANENTFLAGS (response code) 106 7719 PREAUTH (response) 110 7720 PRIVACYREQUIRED (response code) 106 7721 Permanent Flag (class of flag) 13 7722 Predefined keywords 12 7724 R 7725 READ-ONLY (response code) 107 7726 READ-WRITE (response code) 107 7727 RECOMMENDED (specification requirement term) 5 7728 RENAME (command) 42 7729 REQUIRED (specification requirement term) 5 7730 RFC822.SIZE (fetch item) 91 7731 RFC822.SIZE (fetch result) 125 7733 S 7734 SAVE (search result option) 77 7735 SEARCH (command) 76 7736 SEEN (search key) 80 7737 SELECT (command) 36 7738 SENTBEFORE (search key) 80 7739 SENTON (search key) 80 7740 SENTSINCE (search key) 80 7741 SERVERBUG (response code) 107 7742 SHOULD (specification requirement term) 5 7743 SHOULD NOT (specification requirement term) 5 7744 SINCE (search key) 80 7745 SIZE (status item) 69 7746 SMALLER (search key) 80 7747 STARTTLS (command) 28 7748 STATUS (command) 68 7749 STATUS (response) 117 7750 STORE (command) 93 7751 SUBJECT (search key) 80 7752 SUBSCRIBE (command) 44 7753 Session Flag (class of flag) 13 7754 System Flag (type of flag) 12 7756 T 7757 TEXT (part specifier) 91 7758 TEXT (search key) 81 7759 TO (search key) 81 7760 TRYCREATE (response code) 107 7762 U 7763 UID (command) 97 7764 UID (fetch item) 91 7765 UID (fetch result) 125 7766 UID (search key) 81 7767 UIDNEXT (response code) 107 7768 UIDNEXT (status item) 69 7769 UIDNOTSTICKY (response code) 107 7770 UIDVALIDITY (response code) 108 7771 UIDVALIDITY (status item) 69 7772 UNANSWERED (search key) 81 7773 UNAVAILABLE (response code) 108 7774 UNDELETED (search key) 81 7775 UNDRAFT (search key) 81 7776 UNFLAGGED (search key) 81 7777 UNKEYWORD (search key) 81 7778 UNKNOWN-CTE (response code) 108 7779 UNSEEN (search key) 81 7780 UNSEEN (status item) 69 7781 UNSELECT (command) 75 7782 UNSUBSCRIBE (command) 45 7783 Unique Identifier (UID) (message attribute) 9 7785 [ 7786 [RFC-5322] Size (message attribute) 14 7788 \ 7789 \All (mailbox name attribute) 114 7790 \Answered (system flag) 12 7791 \Archive (mailbox name attribute) 114 7792 \Deleted (system flag) 12 7793 \Draft (system flag) 12 7794 \Drafts (mailbox name attribute) 115 7795 \Flagged (mailbox name attribute) 115 7796 \Flagged (system flag) 12 7797 \HasChildren (mailbox name attribute) 113 7798 \HasNoChildren (mailbox name attribute) 113 7799 \Junk (mailbox name attribute) 115 7800 \Marked (mailbox name attribute) 114 7801 \Noinferiors (mailbox name attribute) 113 7802 \NonExistent (mailbox name attribute) 113 7803 \Noselect (mailbox name attribute) 113 7804 \Recent (system flag) 12 7805 \Remote (mailbox name attribute) 114 7806 \Seen (system flag) 12 7807 \Sent (mailbox name attribute) 115 7808 \Subscribed (mailbox name attribute) 114 7809 \Trash (mailbox name attribute) 115 7810 \Unmarked (mailbox name attribute) 114 7812 Authors' Addresses 7814 Alexey Melnikov (editor) 7815 Isode Ltd 7816 14 Castle Mews 7817 Hampton, Middlesex TW12 2NP 7818 UK 7820 Email: Alexey.Melnikov@isode.com 7822 Barry Leiba (editor) 7823 Futurewei Technologies 7825 Phone: +1 646 827 0648 7826 Email: barryleiba@computer.org 7827 URI: http://internetmessagingtechnology.org/