idnits 2.17.1 draft-ietf-extra-imap4rev2-07.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 13 instances of too long lines in the document, the longest one being 9 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 (November 4, 2019) is 1628 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 6318, but not defined == Missing Reference: 'IMAP-OBSOLETE' is mentioned on line 6313, but not defined == Missing Reference: 'IMAP-COMPAT' is mentioned on line 6303, but not defined == Missing Reference: 'IMAP-HISTORICAL' is mentioned on line 6308, but not defined == Missing Reference: 'RFC-822' is mentioned on line 6322, but not defined ** Obsolete undefined reference: RFC 822 (Obsoleted by RFC 2822) == Missing Reference: 'HEADER' is mentioned on line 5155, but not defined == Missing Reference: 'IMAP-DISC' is mentioned on line 6260, but not defined == Missing Reference: 'SMTP' is mentioned on line 6281, but not defined == Missing Reference: 'RFC7888' is mentioned on line 6256, but not defined -- Looks like a reference, but probably isn't: '1' on line 835 == Missing Reference: 'IMAP-URL' is mentioned on line 6295, but not defined == Missing Reference: 'UIDVALIDITY 3857529045' is mentioned on line 5138, but not defined == Missing Reference: 'UIDNEXT 4392' is mentioned on line 1638, but not defined == Missing Reference: 'RFC5258' is mentioned on line 6242, but not defined == Missing Reference: 'RFC2193' is mentioned on line 6247, but not defined == Missing Reference: 'RFC3348' is mentioned on line 6251, but not defined ** Obsolete undefined reference: RFC 3348 (Obsoleted by RFC 5258) == Missing Reference: 'UIDNEXT 2' is mentioned on line 3011, but not defined == Missing Reference: 'UIDVALIDITY 1' is mentioned on line 3082, but not defined == Missing Reference: 'IMAP-I18N' is mentioned on line 6265, but not defined == Missing Reference: 'TEXT' is mentioned on line 5092, but not defined == Missing Reference: 'UID' is mentioned on line 3776, but not defined == Missing Reference: 'RFC4314' is mentioned on line 6288, but not defined == Missing Reference: 'RFC2087' is mentioned on line 6292, but not defined ** Obsolete undefined reference: RFC 2087 (Obsoleted by RFC 9208) == Missing Reference: 'READ-WRITE' is mentioned on line 5139, but not defined == Missing Reference: 'RFC4422' is mentioned on line 5478, but not defined == Missing Reference: 'IMAP4' is mentioned on line 5564, but not defined == Missing Reference: 'Namespace-Response-Extensions' is mentioned on line 5631, but not defined == Missing Reference: 'IMAP-TLS' is mentioned on line 6330, but not defined == Missing Reference: 'IMAP-MODEL' is mentioned on line 6271, but not defined == Missing Reference: 'IMAP-UTF-8' is mentioned on line 6348, but not defined == Missing Reference: 'RFC3516' is mentioned on line 6438, but not defined == Missing Reference: 'RFC-821' is mentioned on line 6326, but not defined ** Obsolete undefined reference: RFC 821 (Obsoleted by RFC 2821) ** Obsolete normative reference: RFC 5246 (ref. 'TLS') (Obsoleted by RFC 8446) ** 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: 10 errors (**), 0 flaws (~~), 33 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 Huawei Technologies 6 Expires: May 7, 2020 November 4, 2019 8 INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev2 9 draft-ietf-extra-imap4rev2-07 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 RFC 6409. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on May 7, 2020. 48 Copyright Notice 50 Copyright (c) 2019 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 This document may contain material from IETF Documents or IETF 64 Contributions published or made publicly available before November 65 10, 2008. The person(s) controlling the copyright in some of this 66 material may not have granted the IETF Trust the right to allow 67 modifications of such material outside the IETF Standards Process. 68 Without obtaining an adequate license from the person(s) controlling 69 the copyright in such materials, this document may not be modified 70 outside the IETF Standards Process, and derivative works of it may 71 not be created outside the IETF Standards Process, except to format 72 it for publication as an RFC or to translate it into languages other 73 than English. 75 Table of Contents 77 1. How to Read This Document . . . . . . . . . . . . . . . . . . 5 78 1.1. Organization of This Document . . . . . . . . . . . . . . 5 79 1.2. Conventions Used in This Document . . . . . . . . . . . . 5 80 1.3. Special Notes to Implementors . . . . . . . . . . . . . . 6 81 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 82 2.1. Link Level . . . . . . . . . . . . . . . . . . . . . . . 7 83 2.2. Commands and Responses . . . . . . . . . . . . . . . . . 7 84 2.2.1. Client Protocol Sender and Server Protocol Receiver . 7 85 2.2.2. Server Protocol Sender and Client Protocol Receiver . 8 86 2.3. Message Attributes . . . . . . . . . . . . . . . . . . . 9 87 2.3.1. Message Numbers . . . . . . . . . . . . . . . . . . . 9 88 2.3.2. Flags Message Attribute . . . . . . . . . . . . . . . 11 89 2.3.3. Internal Date Message Attribute . . . . . . . . . . . 12 90 2.3.4. [RFC-5322] Size Message Attribute . . . . . . . . . . 13 91 2.3.5. Envelope Structure Message Attribute . . . . . . . . 13 92 2.3.6. Body Structure Message Attribute . . . . . . . . . . 13 93 2.4. Message Texts . . . . . . . . . . . . . . . . . . . . . . 13 94 3. State and Flow Diagram . . . . . . . . . . . . . . . . . . . 13 95 3.1. Not Authenticated State . . . . . . . . . . . . . . . . . 13 96 3.2. Authenticated State . . . . . . . . . . . . . . . . . . . 13 97 3.3. Selected State . . . . . . . . . . . . . . . . . . . . . 14 98 3.4. Logout State . . . . . . . . . . . . . . . . . . . . . . 14 99 4. Data Formats . . . . . . . . . . . . . . . . . . . . . . . . 16 100 4.1. Atom . . . . . . . . . . . . . . . . . . . . . . . . . . 16 101 4.1.1. Sequence set and UID set . . . . . . . . . . . . . . 16 102 4.2. Number . . . . . . . . . . . . . . . . . . . . . . . . . 16 103 4.3. String . . . . . . . . . . . . . . . . . . . . . . . . . 16 104 4.3.1. 8-bit and Binary Strings . . . . . . . . . . . . . . 17 105 4.4. Parenthesized List . . . . . . . . . . . . . . . . . . . 18 106 4.5. NIL . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 107 5. Operational Considerations . . . . . . . . . . . . . . . . . 19 108 5.1. Mailbox Naming . . . . . . . . . . . . . . . . . . . . . 19 109 5.1.1. Mailbox Hierarchy Naming . . . . . . . . . . . . . . 20 110 5.1.2. Namespaces . . . . . . . . . . . . . . . . . . . . . 20 111 5.2. Mailbox Size and Message Status Updates . . . . . . . . . 21 112 5.3. Response when no Command in Progress . . . . . . . . . . 22 113 5.4. Autologout Timer . . . . . . . . . . . . . . . . . . . . 22 114 5.5. Multiple Commands in Progress (Command Pipelining) . . . 22 115 6. Client Commands . . . . . . . . . . . . . . . . . . . . . . . 23 116 6.1. Client Commands - Any State . . . . . . . . . . . . . . . 24 117 6.1.1. CAPABILITY Command . . . . . . . . . . . . . . . . . 24 118 6.1.2. NOOP Command . . . . . . . . . . . . . . . . . . . . 25 119 6.1.3. LOGOUT Command . . . . . . . . . . . . . . . . . . . 26 120 6.2. Client Commands - Not Authenticated State . . . . . . . . 26 121 6.2.1. STARTTLS Command . . . . . . . . . . . . . . . . . . 27 122 6.2.2. AUTHENTICATE Command . . . . . . . . . . . . . . . . 28 123 6.2.3. LOGIN Command . . . . . . . . . . . . . . . . . . . . 31 124 6.3. Client Commands - Authenticated State . . . . . . . . . . 31 125 6.3.1. ENABLE Command . . . . . . . . . . . . . . . . . . . 32 126 6.3.2. SELECT Command . . . . . . . . . . . . . . . . . . . 34 127 6.3.3. EXAMINE Command . . . . . . . . . . . . . . . . . . . 35 128 6.3.4. CREATE Command . . . . . . . . . . . . . . . . . . . 36 129 6.3.5. DELETE Command . . . . . . . . . . . . . . . . . . . 37 130 6.3.6. RENAME Command . . . . . . . . . . . . . . . . . . . 38 131 6.3.7. SUBSCRIBE Command . . . . . . . . . . . . . . . . . . 40 132 6.3.8. UNSUBSCRIBE Command . . . . . . . . . . . . . . . . . 41 133 6.3.9. LIST Command . . . . . . . . . . . . . . . . . . . . 41 134 6.3.10. NAMESPACE Command . . . . . . . . . . . . . . . . . . 57 135 6.3.11. STATUS Command . . . . . . . . . . . . . . . . . . . 62 136 6.3.12. APPEND Command . . . . . . . . . . . . . . . . . . . 63 137 6.3.13. IDLE Command . . . . . . . . . . . . . . . . . . . . 66 138 6.4. Client Commands - Selected State . . . . . . . . . . . . 68 139 6.4.1. CLOSE Command . . . . . . . . . . . . . . . . . . . . 68 140 6.4.2. UNSELECT Command . . . . . . . . . . . . . . . . . . 68 141 6.4.3. EXPUNGE Command . . . . . . . . . . . . . . . . . . . 69 142 6.4.4. SEARCH Command . . . . . . . . . . . . . . . . . . . 69 143 6.4.5. FETCH Command . . . . . . . . . . . . . . . . . . . . 75 144 6.4.6. STORE Command . . . . . . . . . . . . . . . . . . . . 79 145 6.4.7. COPY Command . . . . . . . . . . . . . . . . . . . . 80 146 6.4.8. MOVE Command . . . . . . . . . . . . . . . . . . . . 81 147 6.4.9. UID Command . . . . . . . . . . . . . . . . . . . . . 83 148 6.5. Client Commands - Experimental/Expansion . . . . . . . . 85 149 6.5.1. X Command . . . . . . . . . . . . . . . . . . . 85 150 7. Server Responses . . . . . . . . . . . . . . . . . . . . . . 85 151 7.1. Server Responses - Status Responses . . . . . . . . . . . 86 152 7.1.1. OK Response . . . . . . . . . . . . . . . . . . . . . 94 153 7.1.2. NO Response . . . . . . . . . . . . . . . . . . . . . 94 154 7.1.3. BAD Response . . . . . . . . . . . . . . . . . . . . 95 155 7.1.4. PREAUTH Response . . . . . . . . . . . . . . . . . . 95 156 7.1.5. BYE Response . . . . . . . . . . . . . . . . . . . . 95 157 7.2. Server Responses - Server and Mailbox Status . . . . . . 96 158 7.2.1. The ENABLED Response . . . . . . . . . . . . . . . . 96 159 7.2.2. CAPABILITY Response . . . . . . . . . . . . . . . . . 96 160 7.2.3. LIST Response . . . . . . . . . . . . . . . . . . . . 97 161 7.2.4. NAMESPACE Response . . . . . . . . . . . . . . . . . 101 162 7.2.5. STATUS Response . . . . . . . . . . . . . . . . . . . 101 163 7.2.6. ESEARCH Response . . . . . . . . . . . . . . . . . . 101 164 7.2.7. FLAGS Response . . . . . . . . . . . . . . . . . . . 102 165 7.3. Server Responses - Mailbox Size . . . . . . . . . . . . . 102 166 7.3.1. EXISTS Response . . . . . . . . . . . . . . . . . . . 102 167 7.4. Server Responses - Message Status . . . . . . . . . . . . 103 168 7.4.1. EXPUNGE Response . . . . . . . . . . . . . . . . . . 103 169 7.4.2. FETCH Response . . . . . . . . . . . . . . . . . . . 104 170 7.5. Server Responses - Command Continuation Request . . . . . 109 171 8. Sample IMAP4rev2 connection . . . . . . . . . . . . . . . . . 110 172 9. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 111 173 10. Author's Note . . . . . . . . . . . . . . . . . . . . . . . . 128 174 11. Security Considerations . . . . . . . . . . . . . . . . . . . 128 175 11.1. STARTTLS Security Considerations . . . . . . . . . . . . 128 176 11.2. COPYUID and APPENDUID response codes . . . . . . . . . . 129 177 11.3. LIST command and Other Users' namespace . . . . . . . . 129 178 11.4. Other Security Considerations . . . . . . . . . . . . . 129 179 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 130 180 12.1. Updates to IMAP4 Capabilities registry . . . . . . . . . 130 181 12.2. GSSAPI/SASL service name . . . . . . . . . . . . . . . . 131 182 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 131 183 13.1. Normative References . . . . . . . . . . . . . . . . . . 131 184 13.2. Informative References (related protocols) . . . . . . . 134 185 13.3. Informative References (historical aspects of IMAP and 186 related protocols) . . . . . . . . . . . . . . . . . . . 135 187 Appendix A. Backward compatibility with IMAP4rev1 . . . . . . . 136 188 A.1. Mailbox International Naming Convention for compatibility 189 with IMAP4rev1 . . . . . . . . . . . . . . . . . . . . . 136 190 Appendix B. Backward compatibility with BINARY extension . . . . 138 191 Appendix C. Changes from RFC 3501 / IMAP4rev1 . . . . . . . . . 138 192 Appendix D. Acknowledgement . . . . . . . . . . . . . . . . . . 140 193 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 194 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 146 196 1. How to Read This Document 198 1.1. Organization of This Document 200 This document is written from the point of view of the implementor of 201 an IMAP4rev2 client or server. Beyond the protocol overview in 202 section 2, it is not optimized for someone trying to understand the 203 operation of the protocol. The material in sections 3 through 5 204 provides the general context and definitions with which IMAP4rev2 205 operates. 207 Sections 6, 7, and 9 describe the IMAP commands, responses, and 208 syntax, respectively. The relationships among these are such that it 209 is almost impossible to understand any of them separately. In 210 particular, do not attempt to deduce command syntax from the command 211 section alone; instead refer to the Formal Syntax section. 213 1.2. Conventions Used in This Document 215 "Conventions" are basic principles or procedures. Document 216 conventions are noted in this section. 218 In examples, "C:" and "S:" indicate lines sent by the client and 219 server respectively. 221 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 222 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 223 "OPTIONAL" in this document are to be interpreted as described in BCP 224 14 [RFC2119] [RFC8174] when, and only when, they appear in all 225 capitals, as shown here. 227 The word "can" (not "may") is used to refer to a possible 228 circumstance or situation, as opposed to an optional facility of the 229 protocol. 231 "User" is used to refer to a human user, whereas "client" refers to 232 the software being run by the user. 234 "Connection" refers to the entire sequence of client/server 235 interaction from the initial establishment of the network connection 236 until its termination. 238 "Session" refers to the sequence of client/server interaction from 239 the time that a mailbox is selected (SELECT or EXAMINE command) until 240 the time that selection ends (SELECT or EXAMINE of another mailbox, 241 CLOSE command, UNSELECT command, or connection termination). 243 Characters are 7-bit US-ASCII unless otherwise specified. Other 244 character sets are indicated using a "CHARSET", as described in 245 [MIME-IMT] and defined in [CHARSET]. CHARSETs have important 246 additional semantics in addition to defining character set; refer to 247 these documents for more detail. 249 There are several protocol conventions in IMAP. These refer to 250 aspects of the specification which are not strictly part of the IMAP 251 protocol, but reflect generally-accepted practice. Implementations 252 need to be aware of these conventions, and avoid conflicts whether or 253 not they implement the convention. For example, "&" may not be used 254 as a hierarchy delimiter since it conflicts with the Mailbox 255 International Naming Convention, and other uses of "&" in mailbox 256 names are impacted as well. 258 1.3. Special Notes to Implementors 260 Implementors of the IMAP protocol are strongly encouraged to read the 261 IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in 262 conjunction with this document, to help understand the intricacies of 263 this protocol and how best to build an interoperable product. 265 IMAP4rev2 is designed to be upwards compatible from the [IMAP2] and 266 unpublished IMAP2bis protocols. IMAP4rev2 is largely compatible with 267 the IMAP4rev1 protocol described in RFC 3501 and the IMAP4 protocol 268 described in RFC 1730; the exception being in certain facilities 269 added in RFC 1730 that proved problematic and were subsequently 270 removed. In the course of the evolution of IMAP4rev2, some aspects 271 in the earlier protocols have become obsolete. Obsolete commands, 272 responses, and data formats which an IMAP4rev2 implementation can 273 encounter when used with an earlier implementation are described in 274 [IMAP-OBSOLETE]. 276 Other compatibility issues with IMAP2bis, the most common variant of 277 the earlier protocol, are discussed in [IMAP-COMPAT]. A full 278 discussion of compatibility issues with rare (and presumed extinct) 279 variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is 280 primarily of historical interest. 282 IMAP was originally developed for the older [RFC-822] standard, and 283 as a consequence several fetch items in IMAP incorporate "RFC822" in 284 their name. With the exception of RFC822.SIZE, there are more modern 285 replacements; for example, the modern version of RFC822.HEADER is 286 BODY.PEEK[HEADER]. In all cases, "RFC822" should be interpreted as a 287 reference to the updated [RFC-5322] standard. 289 2. Protocol Overview 291 2.1. Link Level 293 The IMAP4rev2 protocol assumes a reliable data stream such as that 294 provided by TCP. When TCP is used, an IMAP4rev2 server listens on 295 port 143. 297 2.2. Commands and Responses 299 An IMAP4rev2 connection consists of the establishment of a client/ 300 server network connection, an initial greeting from the server, and 301 client/server interactions. These client/server interactions consist 302 of a client command, server data, and a server completion result 303 response. 305 All interactions transmitted by client and server are in the form of 306 lines, that is, strings that end with a CRLF. The protocol receiver 307 of an IMAP4rev2 client or server is either reading a line, or is 308 reading a sequence of octets with a known count followed by a line. 310 2.2.1. Client Protocol Sender and Server Protocol Receiver 312 The client command begins an operation. Each client command is 313 prefixed with an identifier (typically a short alphanumeric string, 314 e.g., A0001, A0002, etc.) called a "tag". A different tag is 315 generated by the client for each command. 317 Clients MUST follow the syntax outlined in this specification 318 strictly. It is a syntax error to send a command with missing or 319 extraneous spaces or arguments. 321 There are two cases in which a line from the client does not 322 represent a complete command. In one case, a command argument is 323 quoted with an octet count (see the description of literal in String 324 under Data Formats); in the other case, the command arguments require 325 server feedback (see the AUTHENTICATE command). In either case, the 326 server sends a command continuation request response if it is ready 327 for the octets (if appropriate) and the remainder of the command. 328 This response is prefixed with the token "+". 330 Note: If instead, the server detected an error in the command, it 331 sends a BAD completion response with a tag matching the command 332 (as described below) to reject the command and prevent the client 333 from sending any more of the command. 335 It is also possible for the server to send a completion response 336 for some other command (if multiple commands are in progress), or 337 untagged data. In either case, the command continuation request 338 is still pending; the client takes the appropriate action for the 339 response, and reads another response from the server. In all 340 cases, the client MUST send a complete command (including 341 receiving all command continuation request responses and command 342 continuations for the command) before initiating a new command. 344 The protocol receiver of an IMAP4rev2 server reads a command line 345 from the client, parses the command and its arguments, and transmits 346 server data and a server command completion result response. 348 2.2.2. Server Protocol Sender and Client Protocol Receiver 350 Data transmitted by the server to the client and status responses 351 that do not indicate command completion are prefixed with the token 352 "*", and are called untagged responses. 354 Server data MAY be sent as a result of a client command, or MAY be 355 sent unilaterally by the server. There is no syntactic difference 356 between server data that resulted from a specific command and server 357 data that were sent unilaterally. 359 The server completion result response indicates the success or 360 failure of the operation. It is tagged with the same tag as the 361 client command which began the operation. Thus, if more than one 362 command is in progress, the tag in a server completion response 363 identifies the command to which the response applies. There are 364 three possible server completion responses: OK (indicating success), 365 NO (indicating failure), or BAD (indicating a protocol error such as 366 unrecognized command or command syntax error). 368 Servers SHOULD enforce the syntax outlined in this specification 369 strictly. Any client command with a protocol syntax error, including 370 (but not limited to) missing or extraneous spaces or arguments, 371 SHOULD be rejected, and the client given a BAD server completion 372 response. 374 The protocol receiver of an IMAP4rev2 client reads a response line 375 from the server. It then takes action on the response based upon the 376 first token of the response, which can be a tag, a "*", or a "+". 378 A client MUST be prepared to accept any server response at all times. 379 This includes server data that was not requested. Server data SHOULD 380 be recorded, so that the client can reference its recorded copy 381 rather than sending a command to the server to request the data. In 382 the case of certain server data, the data MUST be recorded. 384 This topic is discussed in greater detail in the Server Responses 385 section. 387 2.3. Message Attributes 389 In addition to message text, each message has several attributes 390 associated with it. These attributes can be retrieved individually 391 or in conjunction with other attributes or message texts. 393 2.3.1. Message Numbers 395 Messages in IMAP4rev2 are accessed by one of two numbers; the unique 396 identifier or the message sequence number. 398 2.3.1.1. Unique Identifier (UID) Message Attribute 400 An unsigned 32-bit value assigned to each message, which when used 401 with the unique identifier validity value (see below) forms a 64-bit 402 value that MUST NOT refer to any other message in the mailbox or any 403 subsequent mailbox with the same name forever. Unique identifiers 404 are assigned in a strictly ascending fashion in the mailbox; as each 405 message is added to the mailbox it is assigned a higher UID than the 406 message(s) which were added previously. Unlike message sequence 407 numbers, unique identifiers are not necessarily contiguous. 409 The unique identifier of a message MUST NOT change during the 410 session, and SHOULD NOT change between sessions. Any change of 411 unique identifiers between sessions MUST be detectable using the 412 UIDVALIDITY mechanism discussed below. Persistent unique identifiers 413 are required for a client to resynchronize its state from a previous 414 session with the server (e.g., disconnected or offline access 415 clients); this is discussed further in [IMAP-DISC]. 417 Associated with every mailbox are two 32-bit unsigned values which 418 aid in unique identifier handling: the next unique identifier value 419 (UIDNEXT) and the unique identifier validity value (UIDVALIDITY). 421 The next unique identifier value is the predicted value that will be 422 assigned to a new message in the mailbox. Unless the unique 423 identifier validity also changes (see below), the next unique 424 identifier value MUST have the following two characteristics. First, 425 the next unique identifier value MUST NOT change unless new messages 426 are added to the mailbox; and second, the next unique identifier 427 value MUST change whenever new messages are added to the mailbox, 428 even if those new messages are subsequently expunged. 430 Note: The next unique identifier value is intended to provide a 431 means for a client to determine whether any messages have been 432 delivered to the mailbox since the previous time it checked this 433 value. It is not intended to provide any guarantee that any 434 message will have this unique identifier. A client can only 435 assume, at the time that it obtains the next unique identifier 436 value, that messages arriving after that time will have a UID 437 greater than or equal to that value. 439 The unique identifier validity value is sent in a UIDVALIDITY 440 response code in an OK untagged response at mailbox selection time. 441 If unique identifiers from an earlier session fail to persist in this 442 session, the unique identifier validity value MUST be greater than 443 the one used in the earlier session. 445 Note: Ideally, unique identifiers SHOULD persist at all times. 446 Although this specification recognizes that failure to persist can 447 be unavoidable in certain server environments, it STRONGLY 448 ENCOURAGES message store implementation techniques that avoid this 449 problem. For example: 451 1. Unique identifiers MUST be strictly ascending in the mailbox 452 at all times. If the physical message store is re-ordered by 453 a non-IMAP agent, this requires that the unique identifiers in 454 the mailbox be regenerated, since the former unique 455 identifiers are no longer strictly ascending as a result of 456 the re-ordering. 458 2. If the message store has no mechanism to store unique 459 identifiers, it must regenerate unique identifiers at each 460 session, and each session must have a unique UIDVALIDITY 461 value. 463 3. If the mailbox is deleted and a new mailbox with the same name 464 is created at a later date, the server must either keep track 465 of unique identifiers from the previous instance of the 466 mailbox, or it must assign a new UIDVALIDITY value to the new 467 instance of the mailbox. A good UIDVALIDITY value to use in 468 this case is a 32-bit representation of the creation date/time 469 of the mailbox. It is alright to use a constant such as 1, 470 but only if it guaranteed that unique identifiers will never 471 be reused, even in the case of a mailbox being deleted (or 472 renamed) and a new mailbox by the same name created at some 473 future time. 475 4. The combination of mailbox name, UIDVALIDITY, and UID must 476 refer to a single immutable message on that server forever. 477 In particular, the internal date, [RFC-5322] size, envelope, 478 body structure, and message texts (RFC822, RFC822.HEADER, 479 RFC822.TEXT, and all BODY[...] fetch data items) must never 480 change. This does not include message numbers, nor does it 481 include attributes that can be set by a STORE command (e.g., 482 FLAGS). 484 2.3.1.2. Message Sequence Number Message Attribute 486 A relative position from 1 to the number of messages in the mailbox. 487 This position MUST be ordered by ascending unique identifier. As 488 each new message is added, it is assigned a message sequence number 489 that is 1 higher than the number of messages in the mailbox before 490 that new message was added. 492 Message sequence numbers can be reassigned during the session. For 493 example, when a message is permanently removed (expunged) from the 494 mailbox, the message sequence number for all subsequent messages is 495 decremented. The number of messages in the mailbox is also 496 decremented. Similarly, a new message can be assigned a message 497 sequence number that was once held by some other message prior to an 498 expunge. 500 In addition to accessing messages by relative position in the 501 mailbox, message sequence numbers can be used in mathematical 502 calculations. For example, if an untagged "11 EXISTS" is received, 503 and previously an untagged "8 EXISTS" was received, three new 504 messages have arrived with message sequence numbers of 9, 10, and 11. 505 Another example, if message 287 in a 523 message mailbox has UID 506 12345, there are exactly 286 messages which have lesser UIDs and 236 507 messages which have greater UIDs. 509 2.3.2. Flags Message Attribute 511 A list of zero or more named tokens associated with the message. A 512 flag is set by its addition to this list, and is cleared by its 513 removal. There are two types of flags in IMAP4rev2. A flag of 514 either type can be permanent or session-only. 516 A system flag is a flag name that is pre-defined in this 517 specification and begin with "\". Certain system flags (\Deleted and 518 \Seen) have special semantics described elsewhere in this document. 519 The currently-defined system flags are: 521 \Seen Message has been read 523 \Answered Message has been answered 525 \Flagged Message is "flagged" for urgent/special attention 527 \Deleted Message is "deleted" for removal by later EXPUNGE 528 \Draft Message has not completed composition (marked as a draft). 530 \Recent This flag was in used in IMAP4rev1 and is now deprecated. 532 A keyword is defined by the server implementation. Keywords do not 533 begin with "\". Servers MAY permit the client to define new keywords 534 in the mailbox (see the description of the PERMANENTFLAGS response 535 code for more information). Some keywords that start with "$" are 536 also defined in this specification. 538 This document defines several keywords that were not originally 539 defined in RFC 3501, but which were found to be useful by client 540 implementations. These keywords SHOULD be supported (i.e. allowed in 541 APPEND, COPY, MOVE and SEARCH commands) by server implementations: 543 $Forwarded Message has been forwarded to another email address, 544 embedded within or attached to a new message. An email client 545 sets this keyword when it successfully forwards the message to 546 another email address. Typical usage of this keyword is to show a 547 different (or additional) icon for a message that has been 548 forwarded. Once set, the flag SHOULD NOT be cleared. 550 $MDNSent Message Disposition Notification [RFC8098] was generated 551 and sent for this message. 553 A flag can be permanent or session-only on a per-flag basis. 554 Permanent flags are those which the client can add or remove from the 555 message flags permanently; that is, concurrent and subsequent 556 sessions will see any change in permanent flags. Changes to session 557 flags are valid only in that session. 559 2.3.3. Internal Date Message Attribute 561 The internal date and time of the message on the server. This is not 562 the date and time in the [RFC-5322] header, but rather a date and 563 time which reflects when the message was received. In the case of 564 messages delivered via [SMTP], this SHOULD be the date and time of 565 final delivery of the message as defined by [SMTP]. In the case of 566 messages delivered by the IMAP4rev2 COPY or MOVE command, this SHOULD 567 be the internal date and time of the source message. In the case of 568 messages delivered by the IMAP4rev2 APPEND command, this SHOULD be 569 the date and time as specified in the APPEND command description. 570 All other cases are implementation defined. 572 2.3.4. [RFC-5322] Size Message Attribute 574 The number of octets in the message, as expressed in [RFC-5322] 575 format. 577 2.3.5. Envelope Structure Message Attribute 579 A parsed representation of the [RFC-5322] header of the message. 580 Note that the IMAP Envelope structure is not the same as an [SMTP] 581 envelope. 583 2.3.6. Body Structure Message Attribute 585 A parsed representation of the [MIME-IMB] body structure information 586 of the message. 588 2.4. Message Texts 590 In addition to being able to fetch the full [RFC-5322] text of a 591 message, IMAP4rev2 permits the fetching of portions of the full 592 message text. Specifically, it is possible to fetch the [RFC-5322] 593 message header, [RFC-5322] message body, a [MIME-IMB] body part, or a 594 [MIME-IMB] header. 596 3. State and Flow Diagram 598 Once the connection between client and server is established, an 599 IMAP4rev2 connection is in one of four states. The initial state is 600 identified in the server greeting. Most commands are only valid in 601 certain states. It is a protocol error for the client to attempt a 602 command while the connection is in an inappropriate state, and the 603 server will respond with a BAD or NO (depending upon server 604 implementation) command completion result. 606 3.1. Not Authenticated State 608 In the not authenticated state, the client MUST supply authentication 609 credentials before most commands will be permitted. This state is 610 entered when a connection starts unless the connection has been pre- 611 authenticated. 613 3.2. Authenticated State 615 In the authenticated state, the client is authenticated and MUST 616 select a mailbox to access before commands that affect messages will 617 be permitted. This state is entered when a pre-authenticated 618 connection starts, when acceptable authentication credentials have 619 been provided, after an error in selecting a mailbox, or after a 620 successful CLOSE command. 622 3.3. Selected State 624 In a selected state, a mailbox has been selected to access. This 625 state is entered when a mailbox has been successfully selected. 627 3.4. Logout State 629 In the logout state, the connection is being terminated. This state 630 can be entered as a result of a client request (via the LOGOUT 631 command) or by unilateral action on the part of either the client or 632 server. 634 If the client requests the logout state, the server MUST send an 635 untagged BYE response and a tagged OK response to the LOGOUT command 636 before the server closes the connection; and the client MUST read the 637 tagged OK response to the LOGOUT command before the client closes the 638 connection. 640 A server SHOULD NOT unilaterally close the connection without sending 641 an untagged BYE response that contains the reason for having done so. 642 A client SHOULD NOT unilaterally close the connection, and instead 643 SHOULD issue a LOGOUT command. If the server detects that the client 644 has unilaterally closed the connection, the server MAY omit the 645 untagged BYE response and simply close its connection. 647 +----------------------+ 648 |connection established| 649 +----------------------+ 650 || 651 \/ 652 +--------------------------------------+ 653 | server greeting | 654 +--------------------------------------+ 655 || (1) || (2) || (3) 656 \/ || || 657 +-----------------+ || || 658 |Not Authenticated| || || 659 +-----------------+ || || 660 || (7) || (4) || || 661 || \/ \/ || 662 || +----------------+ || 663 || | Authenticated |<=++ || 664 || +----------------+ || || 665 || || (7) || (5) || (6) || 666 || || \/ || || 667 || || +--------+ || || 668 || || |Selected|==++ || 669 || || +--------+ || 670 || || || (7) || 671 \/ \/ \/ \/ 672 +--------------------------------------+ 673 | Logout | 674 +--------------------------------------+ 675 || 676 \/ 677 +-------------------------------+ 678 |both sides close the connection| 679 +-------------------------------+ 681 (1) connection without pre-authentication (OK greeting) 682 (2) pre-authenticated connection (PREAUTH greeting) 683 (3) rejected connection (BYE greeting) 684 (4) successful LOGIN or AUTHENTICATE command 685 (5) successful SELECT or EXAMINE command 686 (6) CLOSE command, unsolicited CLOSED response code or 687 failed SELECT or EXAMINE command 688 (7) LOGOUT command, server shutdown, or connection closed 690 4. Data Formats 692 IMAP4rev2 uses textual commands and responses. Data in IMAP4rev2 can 693 be in one of several forms: atom, number, string, parenthesized list, 694 or NIL. Note that a particular data item may take more than one 695 form; for example, a data item defined as using "astring" syntax may 696 be either an atom or a string. 698 4.1. Atom 700 An atom consists of one or more non-special characters. 702 4.1.1. Sequence set and UID set 704 A set of messages can be referenced by a sequence set containing 705 either message sequence numbers or unique identifiers. See Section 9 706 for details. Sequence sets can contain ranges (e.g. "5:50"), an 707 enumeration of specific message/UID numbers, a special symbol "*", or 708 a combination of the above. 710 A "UID set" is similar to the sequence set of unique identifiers; 711 however, the "*" value for a sequence number is not permitted. 713 4.2. Number 715 A number consists of one or more digit characters, and represents a 716 numeric value. 718 4.3. String 720 A string is in one of three forms: synchonizing literal, non- 721 synchronizing literal or quoted string. The synchronizing literal 722 form is the general form of string. The non-synchronizing literal 723 form is also the general form, but has length limitation. The quoted 724 string form is an alternative that avoids the overhead of processing 725 a literal at the cost of limitations of characters which may be used. 727 When the distinction between synchronizing and non-synchronizing 728 literals is not important, this document just uses the term 729 "literal". 731 A synchronizing literal is a sequence of zero or more octets 732 (including CR and LF), prefix-quoted with an octet count in the form 733 of an open brace ("{"), the number of octets, close brace ("}"), and 734 CRLF. In the case of synchronizing literals transmitted from server 735 to client, the CRLF is immediately followed by the octet data. In 736 the case of synchronizing literals transmitted from client to server, 737 the client MUST wait to receive a command continuation request 738 (described later in this document) before sending the octet data (and 739 the remainder of the command). 741 The non-synchronizing literal is an alternate form of synchronizing 742 literal, and it may appear in communication from client to server 743 instead of the synchonizing form of literal. The non-synchronizing 744 literal form MUST NOT be sent from server to client. The non- 745 synchronizing literal is distinguished from the synchronizing literal 746 by having a plus ("+") between the octet count and the closing brace 747 ("}"). The server does not generate a command continuation request 748 in response to a non-synchronizing literal, and clients are not 749 required to wait before sending the octets of a non- synchronizing 750 literal. Non-synchronizing literals MUST NOT be larger than 4096 751 octets. Any literal larger than 4096 bytes MUST be sent as a 752 synchronizing literal. (Non-synchronizing literals defined in this 753 document are the same as non-synchronizing literals defined by the 754 LITERAL- extension from [RFC7888]. See that document for details on 755 how to handle invalid non-synchronizing literals longer than 4096 756 octets and for interaction with other IMAP extensions.) 758 A quoted string is a sequence of zero or more Unicode characters, 759 excluding CR and LF, encoded in UTF-8, with double quote (<">) 760 characters at each end. 762 The empty string is represented as "" (a quoted string with zero 763 characters between double quotes), as {0} followed by CRLF (a 764 synchronizing literal with an octet count of 0) or as {0+} followed 765 by CRLF (a non-synchronizing literal with an octet count of 0). 767 Note: Even if the octet count is 0, a client transmitting a 768 synchronizing literal MUST wait to receive a command continuation 769 request. 771 4.3.1. 8-bit and Binary Strings 773 8-bit textual and binary mail is supported through the use of a 774 [MIME-IMB] content transfer encoding. IMAP4rev2 implementations MAY 775 transmit 8-bit or multi-octet characters in literals, but SHOULD do 776 so only when the [CHARSET] is identified. 778 IMAP4rev2 is compatible with [I18N-HDRS]. As a result, the 779 identified charset for header-field values with 8-bit content is 780 UTF-8 [UTF-8]. IMAP4rev2 implementations MUST accept and MAY 781 transmit [UTF-8] text in quoted-strings as long as the string does 782 not contain NUL, CR, or LF. This differs from IMAP4rev1 783 implementations. 785 Although a BINARY content transfer encoding is defined, unencoded 786 binary strings are not permitted, unless returned in a in 787 response to BINARY.PEEK[]<> or 788 BINARY[]<> FETCH data item. A "binary 789 string" is any string with NUL characters. A string with an 790 excessive amount of CTL characters MAY also be considered to be 791 binary. Unless returned in response to BINARY.PEEK[...]/BINARY[...] 792 FETCH, client and server implementations MUST encode binary data into 793 a textual form, such as BASE64, before transmitting the data. 795 4.4. Parenthesized List 797 Data structures are represented as a "parenthesized list"; a sequence 798 of data items, delimited by space, and bounded at each end by 799 parentheses. A parenthesized list can contain other parenthesized 800 lists, using multiple levels of parentheses to indicate nesting. 802 The empty list is represented as () -- a parenthesized list with no 803 members. 805 4.5. NIL 807 The special form "NIL" represents the non-existence of a particular 808 data item that is represented as a string or parenthesized list, as 809 distinct from the empty string "" or the empty parenthesized list (). 811 Note: NIL is never used for any data item which takes the form of 812 an atom. For example, a mailbox name of "NIL" is a mailbox named 813 NIL as opposed to a non-existent mailbox name. This is because 814 mailbox uses "astring" syntax which is an atom or a string. 815 Conversely, an addr-name of NIL is a non-existent personal name, 816 because addr-name uses "nstring" syntax which is NIL or a string, 817 but never an atom. 819 Examples: 821 The following LIST response: 823 * LIST () "/" NIL 825 is equivalent to: 826 * LIST () "/" "NIL" 828 as LIST response ABNF is using astring for mailbox name. 830 However, the following response 832 * FETCH 1 (BODY[1] NIL) 834 is not equivalent to: 835 * FETCH 1 (BODY[1] "NIL") 836 The former means absence of the body part, while the latter 837 means that it contains literal sequence of characters "NIL". 839 5. Operational Considerations 841 The following rules are listed here to ensure that all IMAP4rev2 842 implementations interoperate properly. 844 5.1. Mailbox Naming 846 In IMAP4rev2, Mailbox names are encoded in Net-Unicode [NET-UNICODE] 847 (this differs from IMAP4rev1). Client implementations MAY attempt to 848 create Net-Unicode mailbox names, and MUST interpret any 8-bit 849 mailbox names returned by LIST as [NET-UNICODE]. Server 850 implementations MUST prohibit the creation of 8-bit mailbox names 851 that do not comply with Net-Unicode (however, servers MAY accept a 852 de-normalized UTF-8 mailbox name and convert it to Net-Unicode prior 853 to mailbox creation). 855 The case-insensitive mailbox name INBOX is a special name reserved to 856 mean "the primary mailbox for this user on this server". (Note that 857 this special name may not exist on some servers for some users, for 858 example if the user has no access to personal namespace.) The 859 interpretation of all other names is implementation-dependent. 861 In particular, this specification takes no position on case 862 sensitivity in non-INBOX mailbox names. Some server implementations 863 are fully case-sensitive in ASCII range; others preserve case of a 864 newly-created name but otherwise are case-insensitive; and yet others 865 coerce names to a particular case. Client implementations MUST 866 interact with any of these. 868 There are certain client considerations when creating a new mailbox 869 name: 871 1. Any character which is one of the atom-specials (see the Formal 872 Syntax) will require that the mailbox name be represented as a 873 quoted string or literal. 875 2. CTL and other non-graphic characters are difficult to represent 876 in a user interface and are best avoided. Servers MAY refuse to 877 create mailbox names containing Unicode CTL characters. 879 3. Although the list-wildcard characters ("%" and "*") are valid in 880 a mailbox name, it is difficult to use such mailbox names with 881 the LIST command due to the conflict with wildcard 882 interpretation. 884 4. Usually, a character (determined by the server implementation) is 885 reserved to delimit levels of hierarchy. 887 5. Two characters, "#" and "&", have meanings by convention, and 888 should be avoided except when used in that convention. 890 5.1.1. Mailbox Hierarchy Naming 892 If it is desired to export hierarchical mailbox names, mailbox names 893 MUST be left-to-right hierarchical using a single character to 894 separate levels of hierarchy. The same hierarchy separator character 895 is used for all levels of hierarchy within a single name. 897 5.1.2. Namespaces 899 Personal Namespace: A namespace that the server considers within the 900 personal scope of the authenticated user on a particular connection. 901 Typically, only the authenticated user has access to mailboxes in 902 their Personal Namespace. It is the part of the namespace that 903 belongs to the user that is allocated for mailboxes. If an INBOX 904 exists for a user, it MUST appear within the user's personal 905 namespace. In the typical case, there SHOULD be only one Personal 906 Namespace on a server. 908 Other Users' Namespace: A namespace that consists of mailboxes from 909 the Personal Namespaces of other users. To access mailboxes in the 910 Other Users' Namespace, the currently authenticated user MUST be 911 explicitly granted access rights. For example, it is common for a 912 manager to grant to their secretary access rights to their mailbox. 913 In the typical case, there SHOULD be only one Other Users' Namespace 914 on a server. 916 Shared Namespace: A namespace that consists of mailboxes that are 917 intended to be shared amongst users and do not exist within a user's 918 Personal Namespace. 920 The namespaces a server uses MAY differ on a per-user basis. 922 5.1.2.1. Historic Mailbox Namespace Naming Convention 924 By convention, the first hierarchical element of any mailbox name 925 which begins with "#" identifies the "namespace" of the remainder of 926 the name. This makes it possible to disambiguate between different 927 types of mailbox stores, each of which have their own namespaces. 929 For example, implementations which offer access to USENET 930 newsgroups MAY use the "#news" namespace to partition the USENET 931 newsgroup namespace from that of other mailboxes. Thus, the 932 comp.mail.misc newsgroup would have a mailbox name of 933 "#news.comp.mail.misc", and the name "comp.mail.misc" can refer to 934 a different object (e.g., a user's private mailbox). 936 Namespaces that include the "#" character are not IMAP URL [IMAP-URL] 937 friendly requiring the "#" character to be represented as %23 when 938 within URLs. As such, server implementers MAY instead consider using 939 namespace prefixes that do not contain the "#" character. 941 5.1.2.2. Common namespace models 943 Previous version of this protocol does not define a default server 944 namespace. Two common namespace models have evolved: 946 The "Personal Mailbox" model, in which the default namespace that is 947 presented consists of only the user's personal mailboxes. To access 948 shared mailboxes, the user must use an escape mechanism to reach 949 another namespace. 951 The "Complete Hierarchy" model, in which the default namespace that 952 is presented includes the user's personal mailboxes along with any 953 other mailboxes they have access to. 955 5.2. Mailbox Size and Message Status Updates 957 At any time, a server can send data that the client did not request. 958 Sometimes, such behavior is REQUIRED. For example, agents other than 959 the server MAY add messages to the mailbox (e.g., new message 960 delivery), change the flags of the messages in the mailbox (e.g., 961 simultaneous access to the same mailbox by multiple agents), or even 962 remove messages from the mailbox. A server MUST send mailbox size 963 updates automatically if a mailbox size change is observed during the 964 processing of a command. A server SHOULD send message flag updates 965 automatically, without requiring the client to request such updates 966 explicitly. 968 Special rules exist for server notification of a client about the 969 removal of messages to prevent synchronization errors; see the 970 description of the EXPUNGE response for more detail. In particular, 971 it is NOT permitted to send an EXISTS response that would reduce the 972 number of messages in the mailbox; only the EXPUNGE response can do 973 this. 975 Regardless of what implementation decisions a client makes on 976 remembering data from the server, a client implementation MUST record 977 mailbox size updates. It MUST NOT assume that any command after the 978 initial mailbox selection will return the size of the mailbox. 980 5.3. Response when no Command in Progress 982 Server implementations are permitted to send an untagged response 983 (except for EXPUNGE) while there is no command in progress. Server 984 implementations that send such responses MUST deal with flow control 985 considerations. Specifically, they MUST either (1) verify that the 986 size of the data does not exceed the underlying transport's available 987 window size, or (2) use non-blocking writes. 989 5.4. Autologout Timer 991 If a server has an inactivity autologout timer that applies to 992 sessions after authentication, the duration of that timer MUST be at 993 least 30 minutes. The receipt of ANY command from the client during 994 that interval SHOULD suffice to reset the autologout timer. 996 5.5. Multiple Commands in Progress (Command Pipelining) 998 The client MAY send another command without waiting for the 999 completion result response of a command, subject to ambiguity rules 1000 (see below) and flow control constraints on the underlying data 1001 stream. Similarly, a server MAY begin processing another command 1002 before processing the current command to completion, subject to 1003 ambiguity rules. However, any command continuation request responses 1004 and command continuations MUST be negotiated before any subsequent 1005 command is initiated. 1007 The exception is if an ambiguity would result because of a command 1008 that would affect the results of other commands. Clients MUST NOT 1009 send multiple commands without waiting if an ambiguity would result. 1010 If the server detects a possible ambiguity, it MUST execute commands 1011 to completion in the order given by the client. 1013 The most obvious example of ambiguity is when a command would affect 1014 the results of another command, e.g., a FETCH of a message's flags 1015 and a STORE of that same message's flags. 1017 A non-obvious ambiguity occurs with commands that permit an untagged 1018 EXPUNGE response (commands other than FETCH, STORE, and SEARCH), 1019 since an untagged EXPUNGE response can invalidate sequence numbers in 1020 a subsequent command. This is not a problem for FETCH, STORE, or 1021 SEARCH commands because servers are prohibited from sending EXPUNGE 1022 responses while any of those commands are in progress. Therefore, if 1023 the client sends any command other than FETCH, STORE, or SEARCH, it 1024 MUST wait for the completion result response before sending a command 1025 with message sequence numbers. 1027 Note: EXPUNGE responses are permitted while UID FETCH, UID STORE, 1028 and UID SEARCH are in progress. If the client sends a UID 1029 command, it MUST wait for a completion result response before 1030 sending a command which uses message sequence numbers (this may 1031 include UID SEARCH). Any message sequence numbers in an argument 1032 to UID SEARCH are associated with messages prior to the effect of 1033 any untagged EXPUNGE returned by the UID SEARCH. 1035 For example, the following non-waiting command sequences are invalid: 1037 FETCH + NOOP + STORE 1039 STORE + COPY + FETCH 1041 COPY + COPY 1043 The following are examples of valid non-waiting command sequences: 1045 FETCH + STORE + SEARCH + NOOP 1047 STORE + COPY + EXPUNGE 1049 UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting 1050 command sequence, depending upon whether or not the second UID 1051 SEARCH contains message sequence numbers. 1053 6. Client Commands 1055 IMAP4rev2 commands are described in this section. Commands are 1056 organized by the state in which the command is permitted. Commands 1057 which are permitted in multiple states are listed in the minimum 1058 permitted state (for example, commands valid in authenticated and 1059 selected state are listed in the authenticated state commands). 1061 Command arguments, identified by "Arguments:" in the command 1062 descriptions below, are described by function, not by syntax. The 1063 precise syntax of command arguments is described in the Formal Syntax 1064 (Section 9). 1066 Some commands cause specific server responses to be returned; these 1067 are identified by "Responses:" in the command descriptions below. 1068 See the response descriptions in the Responses section for 1069 information on these responses, and the Formal Syntax section for the 1070 precise syntax of these responses. It is possible for server data to 1071 be transmitted as a result of any command. Thus, commands that do 1072 not specifically require server data specify "no specific responses 1073 for this command" instead of "none". 1075 The "Result:" in the command description refers to the possible 1076 tagged status responses to a command, and any special interpretation 1077 of these status responses. 1079 The state of a connection is only changed by successful commands 1080 which are documented as changing state. A rejected command (BAD 1081 response) never changes the state of the connection or of the 1082 selected mailbox. A failed command (NO response) generally does not 1083 change the state of the connection or of the selected mailbox; the 1084 exception being the SELECT and EXAMINE commands. 1086 6.1. Client Commands - Any State 1088 The following commands are valid in any state: CAPABILITY, NOOP, and 1089 LOGOUT. 1091 6.1.1. CAPABILITY Command 1093 Arguments: none 1095 Responses: REQUIRED untagged response: CAPABILITY 1097 Result: OK - capability completed 1098 BAD - command unknown or arguments invalid 1100 The CAPABILITY command requests a listing of capabilities that the 1101 server supports. The server MUST send a single untagged CAPABILITY 1102 response with "IMAP4rev2" as one of the listed capabilities before 1103 the (tagged) OK response. 1105 A capability name which begins with "AUTH=" indicates that the server 1106 supports that particular authentication mechanism. All such names 1107 are, by definition, part of this specification. For example, the 1108 authorization capability for an experimental "blurdybloop" 1109 authenticator would be "AUTH=XBLURDYBLOOP" and not 1110 "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP". 1112 Other capability names refer to extensions, revisions, or amendments 1113 to this specification. See the documentation of the CAPABILITY 1114 response for additional information. No capabilities, beyond the 1115 base IMAP4rev2 set defined in this specification, are enabled without 1116 explicit client action to invoke the capability. 1118 Client and server implementations MUST implement the STARTTLS, 1119 LOGINDISABLED, and AUTH=PLAIN (described in [PLAIN]) capabilities. 1120 See the Security Considerations section for important information. 1122 See the section entitled "Client Commands - Experimental/Expansion" 1123 for information about the form of site or implementation-specific 1124 capabilities. 1126 Example: C: abcd CAPABILITY 1127 S: * CAPABILITY IMAP4rev2 STARTTLS AUTH=GSSAPI 1128 LOGINDISABLED 1129 S: abcd OK CAPABILITY completed 1130 C: efgh STARTTLS 1131 S: efgh OK STARTLS completed 1132 1133 C: ijkl CAPABILITY 1134 S: * CAPABILITY IMAP4rev2 AUTH=GSSAPI AUTH=PLAIN 1135 S: ijkl OK CAPABILITY completed 1137 6.1.2. NOOP Command 1139 Arguments: none 1141 Responses: no specific responses for this command (but see below) 1143 Result: OK - noop completed 1144 BAD - command unknown or arguments invalid 1146 The NOOP command always succeeds. It does nothing. 1148 Since any command can return a status update as untagged data, the 1149 NOOP command can be used as a periodic poll for new messages or 1150 message status updates during a period of inactivity (the IDLE 1151 command Section 6.3.13 should be used instead of NOOP if real-time 1152 updates to mailbox state are desirable). The NOOP command can also 1153 be used to reset any inactivity autologout timer on the server. 1155 Example: C: a002 NOOP 1156 S: a002 OK NOOP completed 1157 . . . 1158 C: a047 NOOP 1159 S: * 22 EXPUNGE 1160 S: * 23 EXISTS 1161 S: * 14 FETCH (UID 1305 FLAGS (\Seen \Deleted)) 1162 S: a047 OK NOOP completed 1164 6.1.3. LOGOUT Command 1166 Arguments: none 1168 Responses: REQUIRED untagged response: BYE 1170 Result: OK - logout completed 1171 BAD - command unknown or arguments invalid 1173 The LOGOUT command informs the server that the client is done with 1174 the connection. The server MUST send a BYE untagged response before 1175 the (tagged) OK response, and then close the network connection. 1177 Example: C: A023 LOGOUT 1178 S: * BYE IMAP4rev2 Server logging out 1179 S: A023 OK LOGOUT completed 1180 (Server and client then close the connection) 1182 6.2. Client Commands - Not Authenticated State 1184 In the not authenticated state, the AUTHENTICATE or LOGIN command 1185 establishes authentication and enters the authenticated state. The 1186 AUTHENTICATE command provides a general mechanism for a variety of 1187 authentication techniques, privacy protection, and integrity 1188 checking; whereas the LOGIN command uses a traditional user name and 1189 plaintext password pair and has no means of establishing privacy 1190 protection or integrity checking. 1192 The STARTTLS command is an alternate form of establishing session 1193 privacy protection and integrity checking, but does not by itself 1194 establish authentication or enter the authenticated state. 1196 Server implementations MAY allow access to certain mailboxes without 1197 establishing authentication. This can be done by means of the 1198 ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older 1199 convention is a LOGIN command using the userid "anonymous"; in this 1200 case, a password is required although the server may choose to accept 1201 any password. The restrictions placed on anonymous users are 1202 implementation-dependent. 1204 Once authenticated (including as anonymous), it is not possible to 1205 re-enter not authenticated state. 1207 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 1208 the following commands are valid in the not authenticated state: 1209 STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations 1210 section for important information about these commands. 1212 6.2.1. STARTTLS Command 1214 Arguments: none 1216 Responses: no specific response for this command 1218 Result: OK - starttls completed, begin TLS negotiation 1219 BAD - command unknown or arguments invalid 1221 A [TLS] negotiation begins immediately after the CRLF at the end of 1222 the tagged OK response from the server. Once a client issues a 1223 STARTTLS command, it MUST NOT issue further commands until a server 1224 response is seen and the [TLS] negotiation is complete. 1226 The server remains in the non-authenticated state, even if client 1227 credentials are supplied during the [TLS] negotiation. This does not 1228 preclude an authentication mechanism such as EXTERNAL (defined in 1229 [SASL]) from using client identity determined by the [TLS] 1230 negotiation. 1232 Once [TLS] has been started, the client MUST discard cached 1233 information about server capabilities and SHOULD re-issue the 1234 CAPABILITY command. This is necessary to protect against man-in- 1235 the-middle attacks which alter the capabilities list prior to 1236 STARTTLS. The server MAY advertise different capabilities, and in 1237 particular SHOULD NOT advertise the STARTTLS capability, after a 1238 successful STARTTLS command. 1240 Example: C: a001 CAPABILITY 1241 S: * CAPABILITY IMAP4rev2 STARTTLS LOGINDISABLED 1242 S: a001 OK CAPABILITY completed 1243 C: a002 STARTTLS 1244 S: a002 OK Begin TLS negotiation now 1245 1246 C: a003 CAPABILITY 1247 S: * CAPABILITY IMAP4rev2 AUTH=PLAIN 1248 S: a003 OK CAPABILITY completed 1249 C: a004 LOGIN joe password 1250 S: a004 OK LOGIN completed 1252 6.2.2. AUTHENTICATE Command 1254 Arguments: SASL authentication mechanism name 1255 OPTIONAL initial response 1257 Responses: continuation data can be requested 1259 Result: OK - authenticate completed, now in authenticated state 1260 NO - authenticate failure: unsupported authentication 1261 mechanism, credentials rejected 1262 BAD - command unknown or arguments invalid, 1263 authentication exchange cancelled 1265 The AUTHENTICATE command indicates a [SASL] authentication mechanism 1266 to the server. If the server supports the requested authentication 1267 mechanism, it performs an authentication protocol exchange to 1268 authenticate and identify the client. It MAY also negotiate an 1269 OPTIONAL security layer for subsequent protocol interactions. If the 1270 requested authentication mechanism is not supported, the server 1271 SHOULD reject the AUTHENTICATE command by sending a tagged NO 1272 response. 1274 The AUTHENTICATE command supports the optional "initial response" 1275 feature defined in Section 5.1 of [SASL]. The client doesn't need to 1276 use it. If a SASL mechanism supports "initial response", but it is 1277 not specified by the client, the server handles this as specified in 1278 Section 3 of [SASL]. 1280 The service name specified by this protocol's profile of [SASL] is 1281 "imap". 1283 The authentication protocol exchange consists of a series of server 1284 challenges and client responses that are specific to the 1285 authentication mechanism. A server challenge consists of a command 1286 continuation request response with the "+" token followed by a BASE64 1287 encoded (see Section 4 of [RFC4648]) string. The client response 1288 consists of a single line consisting of a BASE64 encoded string. If 1289 the client wishes to cancel an authentication exchange, it issues a 1290 line consisting of a single "*". If the server receives such a 1291 response, or if it receives an invalid BASE64 string (e.g. 1292 characters outside the BASE64 alphabet, or non-terminal "="), it MUST 1293 reject the AUTHENTICATE command by sending a tagged BAD response. 1295 As with any other client response, this initial response MUST be 1296 encoded as BASE64. It also MUST be transmitted outside of a quoted 1297 string or literal. To send a zero-length initial response, the 1298 client MUST send a single pad character ("="). This indicates that 1299 the response is present, but is a zero-length string. 1301 When decoding the BASE64 data in the initial response, decoding 1302 errors MUST be treated as in any normal SASL client response, i.e. 1303 with a tagged BAD response. In particular, the server should check 1304 for any characters not explicitly allowed by the BASE64 alphabet, as 1305 well as any sequence of BASE64 characters that contains the pad 1306 character ('=') anywhere other than the end of the string (e.g., 1307 "=AAA" and "AAA=BBB" are not allowed). 1309 If the client uses an initial response with a SASL mechanism that 1310 does not support an initial response, the server MUST reject the 1311 command with a tagged BAD response. 1313 If a security layer is negotiated through the [SASL] authentication 1314 exchange, it takes effect immediately following the CRLF that 1315 concludes the authentication exchange for the client, and the CRLF of 1316 the tagged OK response for the server. 1318 While client and server implementations MUST implement the 1319 AUTHENTICATE command itself, it is not required to implement any 1320 authentication mechanisms other than the PLAIN mechanism described in 1321 [PLAIN]. Also, an authentication mechanism is not required to 1322 support any security layers. 1324 Note: a server implementation MUST implement a configuration in 1325 which it does NOT permit any plaintext password mechanisms, unless 1326 either the STARTTLS command has been negotiated or some other 1327 mechanism that protects the session from password snooping has 1328 been provided. Server sites SHOULD NOT use any configuration 1329 which permits a plaintext password mechanism without such a 1330 protection mechanism against password snooping. Client and server 1331 implementations SHOULD implement additional [SASL] mechanisms that 1332 do not use plaintext passwords, such the GSSAPI mechanism 1333 described in [SASL] and/or the SCRAM-SHA-256/SCRAM-SHA-256-PLUS 1334 [SCRAM-SHA-256] mechanisms. 1336 Servers and clients can support multiple authentication mechanisms. 1337 The server SHOULD list its supported authentication mechanisms in the 1338 response to the CAPABILITY command so that the client knows which 1339 authentication mechanisms to use. 1341 A server MAY include a CAPABILITY response code in the tagged OK 1342 response of a successful AUTHENTICATE command in order to send 1343 capabilities automatically. It is unnecessary for a client to send a 1344 separate CAPABILITY command if it recognizes these automatic 1345 capabilities. This should only be done if a security layer was not 1346 negotiated by the AUTHENTICATE command, because the tagged OK 1347 response as part of an AUTHENTICATE command is not protected by 1348 encryption/integrity checking. [SASL] requires the client to re- 1349 issue a CAPABILITY command in this case. The server MAY advertise 1350 different capabilities after a successful AUTHENTICATE command. 1352 If an AUTHENTICATE command fails with a NO response, the client MAY 1353 try another authentication mechanism by issuing another AUTHENTICATE 1354 command. It MAY also attempt to authenticate by using the LOGIN 1355 command (see Section 6.2.3 for more detail). In other words, the 1356 client MAY request authentication types in decreasing order of 1357 preference, with the LOGIN command as a last resort. 1359 The authorization identity passed from the client to the server 1360 during the authentication exchange is interpreted by the server as 1361 the user name whose privileges the client is requesting. 1363 Example: S: * OK IMAP4rev2 Server 1364 C: A001 AUTHENTICATE GSSAPI 1365 S: + 1366 C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw 1367 MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0 1368 b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW 1369 Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA 1370 cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX 1371 AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y 1372 C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb 1373 I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi 1374 vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL 1375 pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n 1376 FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE 1377 NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx 1378 O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB 1379 vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg== 1380 S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC 1381 AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0 1382 uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg== 1383 C: 1384 S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe 1385 ceP2CWY0SR0fAQAgAAQEBAQ= 1386 C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP 1387 wkhbfa2QteAQAgAG1yYwE= 1388 S: A001 OK GSSAPI authentication successful 1390 Note: The line breaks within server challenges and client responses 1391 are for editorial clarity and are not in real authenticators. 1393 6.2.3. LOGIN Command 1395 Arguments: user name 1396 password 1398 Responses: no specific responses for this command 1400 Result: OK - login completed, now in authenticated state 1401 NO - login failure: user name or password rejected 1402 BAD - command unknown or arguments invalid 1404 The LOGIN command identifies the client to the server and carries the 1405 plaintext password authenticating this user. 1407 A server MAY include a CAPABILITY response code in the tagged OK 1408 response to a successful LOGIN command in order to send capabilities 1409 automatically. It is unnecessary for a client to send a separate 1410 CAPABILITY command if it recognizes these automatic capabilities. 1412 Example: C: a001 LOGIN SMITH SESAME 1413 S: a001 OK LOGIN completed 1415 Note: Use of the LOGIN command over an insecure network (such as the 1416 Internet) is a security risk, because anyone monitoring network 1417 traffic can obtain plaintext passwords. The LOGIN command SHOULD NOT 1418 be used except as a last resort, and it is recommended that client 1419 implementations have a means to disable any automatic use of the 1420 LOGIN command. 1422 Unless either the client is accessing IMAP service on IMAPS port 1423 [RFC8314], the STARTTLS command has been negotiated or some other 1424 mechanism that protects the session from password snooping has been 1425 provided, a server implementation MUST implement a configuration in 1426 which it advertises the LOGINDISABLED capability and does NOT permit 1427 the LOGIN command. Server sites SHOULD NOT use any configuration 1428 which permits the LOGIN command without such a protection mechanism 1429 against password snooping. A client implementation MUST NOT send a 1430 LOGIN command if the LOGINDISABLED capability is advertised. 1432 6.3. Client Commands - Authenticated State 1434 In the authenticated state, commands that manipulate mailboxes as 1435 atomic entities are permitted. Of these commands, the SELECT and 1436 EXAMINE commands will select a mailbox for access and enter the 1437 selected state. 1439 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 1440 the following commands are valid in the authenticated state: ENABLE, 1441 SELECT, EXAMINE, NAMESPACE, CREATE, DELETE, RENAME, SUBSCRIBE, 1442 UNSUBSCRIBE, LIST, STATUS, APPEND and IDLE. 1444 6.3.1. ENABLE Command 1446 Arguments: capability names 1448 Responses: no specific responses for this command 1450 Result: OK - Relevant capabilities enabled 1451 BAD - No arguments, or syntax error in an argument 1453 Several IMAP extensions allow the server to return unsolicited 1454 responses specific to these extensions in certain circumstances. 1455 However, servers cannot send those unsolicited responses (with the 1456 exception of response codes (see Section 7.1) included in tagged or 1457 untagged OK/NO/BAD responses, which can always be sent) until they 1458 know that the clients support such extensions and thus won't choke on 1459 the extension response data. 1461 The ENABLE command provides an explicit indication from the client 1462 that it supports particular extensions. 1464 The ENABLE command takes a list of capability names, and requests the 1465 server to enable the named extensions. Once enabled using ENABLE, 1466 each extension remains active until the IMAP connection is closed. 1467 For each argument, the server does the following: 1469 o If the argument is not an extension known to the server, the 1470 server MUST ignore the argument. 1472 o If the argument is an extension known to the server, and it is not 1473 specifically permitted to be enabled using ENABLE, the server MUST 1474 ignore the argument. (Note that knowing about an extension 1475 doesn't necessarily imply supporting that extension.) 1477 o If the argument is an extension that is supported by the server 1478 and that needs to be enabled, the server MUST enable the extension 1479 for the duration of the connection. Note that once an extension 1480 is enabled, there is no way to disable it. 1482 If the ENABLE command is successful, the server MUST send an untagged 1483 ENABLED response Section 7.2.1. 1485 Clients SHOULD only include extensions that need to be enabled by the 1486 server. For example, a client can enable IMAP4rev2 specific 1487 behaviour when both IMAP4rev1 and IMAP4rev2 are advertised in the 1488 CAPABILITY response. Future RFCs may add to this list. 1490 The ENABLE command is only valid in the authenticated state, before 1491 any mailbox is selected. Clients MUST NOT issue ENABLE once they 1492 SELECT/EXAMINE a mailbox; however, server implementations don't have 1493 to check that no mailbox is selected or was previously selected 1494 during the duration of a connection. 1496 The ENABLE command can be issued multiple times in a session. It is 1497 additive; i.e., "ENABLE a b", followed by "ENABLE c" is the same as a 1498 single command "ENABLE a b c". When multiple ENABLE commands are 1499 issued, each corresponding ENABLED response SHOULD only contain 1500 extensions enabled by the corresponding ENABLE command. 1502 There are no limitations on pipelining ENABLE. For example, it is 1503 possible to send ENABLE and then immediately SELECT, or a LOGIN 1504 immediately followed by ENABLE. 1506 The server MUST NOT change the CAPABILITY list as a result of 1507 executing ENABLE; i.e., a CAPABILITY command issued right after an 1508 ENABLE command MUST list the same capabilities as a CAPABILITY 1509 command issued before the ENABLE command. This is demonstrated in 1510 the following example: 1512 C: t1 CAPABILITY 1513 S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA 1514 S: t1 OK foo 1515 C: t2 ENABLE CONDSTORE X-GOOD-IDEA 1516 S: * ENABLED X-GOOD-IDEA 1517 S: t2 OK foo 1518 C: t3 CAPABILITY 1519 S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA 1520 S: t3 OK foo again 1522 In the following example, the client enables CONDSTORE: 1524 C: a1 ENABLE CONDSTORE 1525 S: * ENABLED CONDSTORE 1526 S: a1 OK Conditional Store enabled 1528 6.3.1.1. Note to Designers of Extensions That May Use the ENABLE 1529 Command 1531 Designers of IMAP extensions are discouraged from creating extensions 1532 that require ENABLE unless there is no good alternative design. 1533 Specifically, extensions that cause potentially incompatible behavior 1534 changes to deployed server responses (and thus benefit from ENABLE) 1535 have a higher complexity cost than extensions that do not. 1537 6.3.2. SELECT Command 1539 Arguments: mailbox name 1541 Responses: REQUIRED untagged responses: FLAGS, EXISTS 1542 REQUIRED OK untagged responses: PERMANENTFLAGS, 1543 UIDNEXT, UIDVALIDITY 1545 Result: OK - select completed, now in selected state 1546 NO - select failure, now in authenticated state: no 1547 such mailbox, can't access mailbox 1548 BAD - command unknown or arguments invalid 1550 The SELECT command selects a mailbox so that messages in the mailbox 1551 can be accessed. Before returning an OK to the client, the server 1552 MUST send the following untagged data to the client. Note that 1553 earlier versions of this protocol only required the FLAGS and EXISTS 1554 untagged data; consequently, client implementations SHOULD implement 1555 default behavior for missing data as discussed with the individual 1556 item. 1558 FLAGS Defined flags in the mailbox. See the description of the 1559 FLAGS response for more detail. 1561 EXISTS The number of messages in the mailbox. See the 1562 description of the EXISTS response for more detail. 1564 OK [PERMANENTFLAGS ()] A list of message flags that 1565 the client can change permanently. If this is missing, the client 1566 should assume that all flags can be changed permanently. 1568 OK [UIDNEXT ] The next unique identifier value. Refer to 1569 Section 2.3.1.1 for more information. If this is missing, the 1570 client can not make any assumptions about the next unique 1571 identifier value. 1573 OK [UIDVALIDITY ] The unique identifier validity value. Refer to 1574 Section 2.3.1.1 for more information. If this is missing, the 1575 server does not support unique identifiers. 1577 Only one mailbox can be selected at a time in a connection; 1578 simultaneous access to multiple mailboxes requires multiple 1579 connections. The SELECT command automatically deselects any 1580 currently selected mailbox before attempting the new selection. 1581 Consequently, if a mailbox is selected and a SELECT command that 1582 fails is attempted, no mailbox is selected. When deselecting a 1583 selected mailbox, the server MUST return an untagged OK response with 1584 the "[CLOSED]" response code when the currently selected mailbox is 1585 closed (see Paragraph 10). 1587 If the client is permitted to modify the mailbox, the server SHOULD 1588 prefix the text of the tagged OK response with the "[READ-WRITE]" 1589 response code. 1591 If the client is not permitted to modify the mailbox but is permitted 1592 read access, the mailbox is selected as read-only, and the server 1593 MUST prefix the text of the tagged OK response to SELECT with the 1594 "[READ-ONLY]" response code. Read-only access through SELECT differs 1595 from the EXAMINE command in that certain read-only mailboxes MAY 1596 permit the change of permanent state on a per-user (as opposed to 1597 global) basis. Netnews messages marked in a server-based .newsrc 1598 file are an example of such per-user permanent state that can be 1599 modified with read-only mailboxes. 1601 Example: C: A142 SELECT INBOX 1602 S: * 172 EXISTS 1603 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1604 S: * OK [UIDNEXT 4392] Predicted next UID 1605 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1606 S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited 1607 S: A142 OK [READ-WRITE] SELECT completed 1609 Note that IMAP4rev1 compliant servers can also send the untagged 1610 RECENT response which was depractated in IMAP4rev2. E.g. "* 0 1611 RECENT". Pure IMAP4rev2 clients are advised to ignore the untagged 1612 RECENT response. 1614 6.3.3. EXAMINE Command 1616 Arguments: mailbox name 1618 Responses: REQUIRED untagged responses: FLAGS, EXISTS 1619 REQUIRED OK untagged responses: PERMANENTFLAGS, 1620 UIDNEXT, UIDVALIDITY 1622 Result: OK - examine completed, now in selected state 1623 NO - examine failure, now in authenticated state: no 1624 such mailbox, can't access mailbox BAD - command unknown 1625 or arguments invalid 1627 The EXAMINE command is identical to SELECT and returns the same 1628 output; however, the selected mailbox is identified as read-only. No 1629 changes to the permanent state of the mailbox, including per-user 1630 state, are permitted. 1632 The text of the tagged OK response to the EXAMINE command MUST begin 1633 with the "[READ-ONLY]" response code. 1635 Example: C: A932 EXAMINE blurdybloop 1636 S: * 17 EXISTS 1637 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1638 S: * OK [UIDNEXT 4392] Predicted next UID 1639 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1640 S: * OK [PERMANENTFLAGS ()] No permanent flags permitted 1641 S: A932 OK [READ-ONLY] EXAMINE completed 1643 6.3.4. CREATE Command 1645 Arguments: mailbox name 1647 Responses: no specific responses for this command 1649 Result: OK - create completed 1650 NO - create failure: can't create mailbox with that name 1651 BAD - command unknown or arguments invalid 1653 The CREATE command creates a mailbox with the given name. An OK 1654 response is returned only if a new mailbox with that name has been 1655 created. It is an error to attempt to create INBOX or a mailbox with 1656 a name that refers to an extant mailbox. Any error in creation will 1657 return a tagged NO response. If a client attempts to create a UTF-8 1658 mailbox name that is not a valid Net-Unicode name, the server MUST 1659 reject the creation or convert the name to Net-Unicode prior to 1660 creating the mailbox. 1662 If the mailbox name is suffixed with the server's hierarchy separator 1663 character (as returned from the server by a LIST command), this is a 1664 declaration that the client intends to create mailbox names under 1665 this name in the hierarchy. Server implementations that do not 1666 require this declaration MUST ignore the declaration. In any case, 1667 the name created is without the trailing hierarchy delimiter. 1669 If the server's hierarchy separator character appears elsewhere in 1670 the name, the server SHOULD create any superior hierarchical names 1671 that are needed for the CREATE command to be successfully completed. 1672 In other words, an attempt to create "foo/bar/zap" on a server in 1673 which "/" is the hierarchy separator character SHOULD create foo/ and 1674 foo/bar/ if they do not already exist. 1676 If a new mailbox is created with the same name as a mailbox which was 1677 deleted, its unique identifiers MUST be greater than any unique 1678 identifiers used in the previous incarnation of the mailbox UNLESS 1679 the new incarnation has a different unique identifier validity value. 1680 See the description of the UID command for more detail. 1682 Example: C: A003 CREATE owatagusiam/ 1683 S: A003 OK CREATE completed 1684 C: A004 CREATE owatagusiam/blurdybloop 1685 S: A004 OK CREATE completed 1687 Note: The interpretation of this example depends on whether "/" 1688 was returned as the hierarchy separator from LIST. If "/" is the 1689 hierarchy separator, a new level of hierarchy named "owatagusiam" 1690 with a member called "blurdybloop" is created. Otherwise, two 1691 mailboxes at the same hierarchy level are created. 1693 6.3.5. DELETE Command 1695 Arguments: mailbox name 1697 Responses: no specific responses for this command 1699 Result: OK - delete completed 1700 NO - delete failure: can't delete mailbox with that name 1701 BAD - command unknown or arguments invalid 1703 The DELETE command permanently removes the mailbox with the given 1704 name. A tagged OK response is returned only if the mailbox has been 1705 deleted. It is an error to attempt to delete INBOX or a mailbox name 1706 that does not exist. 1708 The DELETE command MUST NOT remove inferior hierarchical names. For 1709 example, if a mailbox "foo" has an inferior "foo.bar" (assuming "." 1710 is the hierarchy delimiter character), removing "foo" MUST NOT remove 1711 "foo.bar". It is an error to attempt to delete a name that has 1712 inferior hierarchical names and also has the \Noselect mailbox name 1713 attribute (see the description of the LIST response for more 1714 details). 1716 It is permitted to delete a name that has inferior hierarchical names 1717 and does not have the \Noselect mailbox name attribute. If the 1718 server implementation does not permit deleting the name while 1719 inferior hierarchical names exists the \Noselect mailbox name 1720 attribute is set for that name. In any case, all messages in that 1721 mailbox are removed by the DELETE command. 1723 The value of the highest-used unique identifier of the deleted 1724 mailbox MUST be preserved so that a new mailbox created with the same 1725 name will not reuse the identifiers of the former incarnation, UNLESS 1726 the new incarnation has a different unique identifier validity value. 1727 See the description of the UID command for more detail. 1729 Examples: C: A682 LIST "" * 1730 S: * LIST () "/" blurdybloop 1731 S: * LIST (\Noselect) "/" foo 1732 S: * LIST () "/" foo/bar 1733 S: A682 OK LIST completed 1734 C: A683 DELETE blurdybloop 1735 S: A683 OK DELETE completed 1736 C: A684 DELETE foo 1737 S: A684 NO Name "foo" has inferior hierarchical names 1738 C: A685 DELETE foo/bar 1739 S: A685 OK DELETE Completed 1740 C: A686 LIST "" * 1741 S: * LIST (\Noselect) "/" foo 1742 S: A686 OK LIST completed 1743 C: A687 DELETE foo 1744 S: A687 OK DELETE Completed 1745 C: A82 LIST "" * 1746 S: * LIST () "." blurdybloop 1747 S: * LIST () "." foo 1748 S: * LIST () "." foo.bar 1749 S: A82 OK LIST completed 1750 C: A83 DELETE blurdybloop 1751 S: A83 OK DELETE completed 1752 C: A84 DELETE foo 1753 S: A84 OK DELETE Completed 1754 C: A85 LIST "" * 1755 S: * LIST () "." foo.bar 1756 S: A85 OK LIST completed 1757 C: A86 LIST "" % 1758 S: * LIST (\Noselect) "." foo 1759 S: A86 OK LIST completed 1761 6.3.6. RENAME Command 1763 Arguments: existing mailbox name 1764 new mailbox name 1766 Responses: no specific responses for this command 1768 Result: OK - rename completed 1769 NO - rename failure: can't rename mailbox with that name, 1770 can't rename to mailbox with that name 1771 BAD - command unknown or arguments invalid 1773 The RENAME command changes the name of a mailbox. A tagged OK 1774 response is returned only if the mailbox has been renamed. It is an 1775 error to attempt to rename from a mailbox name that does not exist or 1776 to a mailbox name that already exists. Any error in renaming will 1777 return a tagged NO response. 1779 If the name has inferior hierarchical names, then the inferior 1780 hierarchical names MUST also be renamed. For example, a rename of 1781 "foo" to "zap" will rename "foo/bar" (assuming "/" is the hierarchy 1782 delimiter character) to "zap/bar". 1784 If the server's hierarchy separator character appears in the name, 1785 the server SHOULD create any superior hierarchical names that are 1786 needed for the RENAME command to complete successfully. In other 1787 words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a 1788 server in which "/" is the hierarchy separator character SHOULD 1789 create baz/ and baz/rag/ if they do not already exist. 1791 The value of the highest-used unique identifier of the old mailbox 1792 name MUST be preserved so that a new mailbox created with the same 1793 name will not reuse the identifiers of the former incarnation, UNLESS 1794 the new incarnation has a different unique identifier validity value. 1795 See the description of the UID command for more detail. 1797 Renaming INBOX is permitted, and has special behavior. It moves all 1798 messages in INBOX to a new mailbox with the given name, leaving INBOX 1799 empty. If the server implementation supports inferior hierarchical 1800 names of INBOX, these are unaffected by a rename of INBOX. 1802 Examples: C: A682 LIST "" * 1803 S: * LIST () "/" blurdybloop 1804 S: * LIST (\Noselect) "/" foo 1805 S: * LIST () "/" foo/bar 1806 S: A682 OK LIST completed 1807 C: A683 RENAME blurdybloop sarasoop 1808 S: A683 OK RENAME completed 1809 C: A684 RENAME foo zowie 1810 S: A684 OK RENAME Completed 1811 C: A685 LIST "" * 1812 S: * LIST () "/" sarasoop 1813 S: * LIST (\Noselect) "/" zowie 1814 S: * LIST () "/" zowie/bar 1815 S: A685 OK LIST completed 1817 C: Z432 LIST "" * 1818 S: * LIST () "." INBOX 1819 S: * LIST () "." INBOX.bar 1820 S: Z432 OK LIST completed 1821 C: Z433 RENAME INBOX old-mail 1822 S: Z433 OK RENAME completed 1823 C: Z434 LIST "" * 1824 S: * LIST () "." INBOX 1825 S: * LIST () "." INBOX.bar 1826 S: * LIST () "." old-mail 1827 S: Z434 OK LIST completed 1829 6.3.7. SUBSCRIBE Command 1831 Arguments: mailbox 1833 Responses: no specific responses for this command 1835 Result: OK - subscribe completed 1836 NO - subscribe failure: can't subscribe to that name 1837 BAD - command unknown or arguments invalid 1839 The SUBSCRIBE command adds the specified mailbox name to the server's 1840 set of "active" or "subscribed" mailboxes as returned by the LIST 1841 (SUBSCRIBED) command. This command returns a tagged OK response only 1842 if the subscription is successful. 1844 A server MAY validate the mailbox argument to SUBSCRIBE to verify 1845 that it exists. However, it MUST NOT unilaterally remove an existing 1846 mailbox name from the subscription list even if a mailbox by that 1847 name no longer exists. 1849 Note: This requirement is because a server site can choose to 1850 routinely remove a mailbox with a well-known name (e.g., "system- 1851 alerts") after its contents expire, with the intention of 1852 recreating it when new contents are appropriate. 1854 Example: C: A002 SUBSCRIBE #news.comp.mail.mime 1855 S: A002 OK SUBSCRIBE completed 1857 6.3.8. UNSUBSCRIBE Command 1859 Arguments: mailbox name 1861 Responses: no specific responses for this command 1863 Result: OK - unsubscribe completed 1864 NO - unsubscribe failure: can't unsubscribe that name 1865 BAD - command unknown or arguments invalid 1867 The UNSUBSCRIBE command removes the specified mailbox name from the 1868 server's set of "active" or "subscribed" mailboxes as returned by the 1869 LIST (SUBSCRIBED) command. This command returns a tagged OK response 1870 only if the unsubscription is successful. 1872 Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime 1873 S: A002 OK UNSUBSCRIBE completed 1875 6.3.9. LIST Command 1877 Arguments (basic): reference name 1878 mailbox name with possible wildcards 1880 Arguments (extended): selection options (OPTIONAL) 1881 reference name 1882 mailbox patterns 1883 return options (OPTIONAL) 1885 Responses: untagged responses: LIST 1887 Result: OK - list completed 1888 NO - list failure: can't list that reference or name 1889 BAD - command unknown or arguments invalid 1891 The LIST command returns a subset of names from the complete set of 1892 all names available to the client. Zero or more untagged LIST 1893 replies are returned, containing the name attributes, hierarchy 1894 delimiter, name, and possible extension information; see the 1895 description of the LIST reply for more detail. 1897 The LIST command SHOULD return its data quickly, without undue delay. 1898 For example, it SHOULD NOT go to excess trouble to calculate the 1899 \Marked or \Unmarked status or perform other processing; if each name 1900 requires 1 second of processing, then a list of 1200 names would take 1901 20 minutes! 1903 The extended LIST command, originally introduced in [RFC5258], 1904 provides capabilities beyond that of the original IMAP LIST command. 1905 The extended syntax is being used if one or more of the following 1906 conditions is true: 1908 1. if the first word after the command name begins with a 1909 parenthesis ("LIST selection options") 1911 2. if the second word after the command name begins with a 1912 parenthesis ("multiple mailbox patterns") 1914 3. if the LIST command has more than 2 parameters ("LIST return 1915 options") 1917 An empty ("" string) reference name argument indicates that the 1918 mailbox name is interpreted as by SELECT. The returned mailbox names 1919 MUST match the supplied mailbox name pattern(s). A non-empty 1920 reference name argument is the name of a mailbox or a level of 1921 mailbox hierarchy, and indicates the context in which the mailbox 1922 name is interpreted. Clients SHOULD use the empty reference 1923 argument. 1925 In the basic syntax only, an empty ("" string) mailbox name argument 1926 is a special request to return the hierarchy delimiter and the root 1927 name of the name given in the reference. The value returned as the 1928 root MAY be the empty string if the reference is non-rooted or is an 1929 empty string. In all cases, a hierarchy delimiter (or NIL if there 1930 is no hierarchy) is returned. This permits a client to get the 1931 hierarchy delimiter (or find out that the mailbox names are flat) 1932 even when no mailboxes by that name currently exist. 1934 In the extended syntax, any mailbox name arguments that are empty 1935 strings are ignored. There is no special meaning for empty mailbox 1936 names when the extended syntax is used. 1938 The reference and mailbox name arguments are interpreted into a 1939 canonical form that represents an unambiguous left-to-right 1940 hierarchy. The returned mailbox names will be in the interpreted 1941 form, that we call "canonical LIST pattern" later in this document. 1942 To define the term "canonical LIST pattern" formally: it refers to 1943 the canonical pattern constructed internally by the server from the 1944 reference and mailbox name arguments. 1946 Note: The interpretation of the reference argument is 1947 implementation-defined. It depends upon whether the server 1948 implementation has a concept of the "current working directory" 1949 and leading "break out characters", which override the current 1950 working directory. 1952 For example, on a server which exports a UNIX or NT filesystem, 1953 the reference argument contains the current working directory, and 1954 the mailbox name argument would contain the name as interpreted in 1955 the current working directory. 1957 If a server implementation has no concept of break out characters, 1958 the canonical form is normally the reference name appended with 1959 the mailbox name. Note that if the server implements the 1960 namespace convention (Section 5.1.2.1), "#" is a break out 1961 character and must be treated as such. 1963 If the reference argument is not a level of mailbox hierarchy 1964 (that is, it is a \NoInferiors name), and/or the reference 1965 argument does not end with the hierarchy delimiter, it is 1966 implementation-dependent how this is interpreted. For example, a 1967 reference of "foo/bar" and mailbox name of "rag/baz" could be 1968 interpreted as "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/ 1969 baz". A client SHOULD NOT use such a reference argument except at 1970 the explicit request of the user. A hierarchical browser MUST NOT 1971 make any assumptions about server interpretation of the reference 1972 unless the reference is a level of mailbox hierarchy AND ends with 1973 the hierarchy delimiter. 1975 Any part of the reference argument that is included in the 1976 interpreted form SHOULD prefix the interpreted form. It SHOULD also 1977 be in the same form as the reference name argument. This rule 1978 permits the client to determine if the returned mailbox name is in 1979 the context of the reference argument, or if something about the 1980 mailbox argument overrode the reference argument. Without this rule, 1981 the client would have to have knowledge of the server's naming 1982 semantics including what characters are "breakouts" that override a 1983 naming context. 1985 For example, here are some examples of how references 1986 and mailbox names might be interpreted on a UNIX-based 1987 server: 1989 Reference Mailbox Name Interpretation 1990 ------------ ------------ -------------- 1991 ~smith/Mail/ foo.* ~smith/Mail/foo.* 1992 archive/ % archive/% 1993 #news. comp.mail.* #news.comp.mail.* 1994 ~smith/Mail/ /usr/doc/foo /usr/doc/foo 1995 archive/ ~fred/Mail/* ~fred/Mail/* 1997 The first three examples demonstrate interpretations in 1998 the context of the reference argument. Note that 1999 "~smith/Mail" SHOULD NOT be transformed into something 2000 like "/u2/users/smith/Mail", or it would be impossible 2001 for the client to determine that the interpretation was 2002 in the context of the reference. 2004 The character "*" is a wildcard, and matches zero or more characters 2005 at this position. The character "%" is similar to "*", but it does 2006 not match a hierarchy delimiter. If the "%" wildcard is the last 2007 character of a mailbox name argument, matching levels of hierarchy 2008 are also returned. If these levels of hierarchy are not also 2009 selectable mailboxes, they are returned with the \Noselect mailbox 2010 name attribute (see the description of the LIST response for more 2011 details). 2013 If multiple mailbox patterns are used (in the extended syntax), a 2014 mailbox matches if it matches at least one mailbox pattern. If a 2015 mailbox matches more than one pattern, it is still only returned 2016 once. Any syntactically valid pattern that is not accepted by a 2017 server for any reason MUST be silently ignored. 2019 Selection options tell the server to limit the mailbox names that are 2020 selected by the LIST operation. If selection options are used, the 2021 mailboxes returned are those that match both the list of canonical 2022 LIST patterns and the selection options. Unless a particular 2023 selection option provides special rules, the selection options are 2024 cumulative: a mailbox that matches the mailbox patterns is selected 2025 only if it also matches all of the selection options. (An example of 2026 a selection option with special rules is the RECURSIVEMATCH option.) 2028 Return options control what information is returned for each matched 2029 mailbox. Return options MUST NOT cause the server to report 2030 information about additional mailbox names other than those that 2031 match the canonical LIST patterns and selection options. If no 2032 return options are specified, the client is only expecting 2033 information about mailbox attributes. The server MAY return other 2034 information about the matched mailboxes, and clients MUST be able to 2035 handle that situation. 2037 Initial selection options and return options are defined in the 2038 following subsections, and new ones will also be defined in 2039 extensions. Initial options defined in this document MUST be 2040 supported. Each non-initial option will be enabled by a capability 2041 string (one capability may enable multiple options), and a client 2042 MUST NOT send an option for which the server has not advertised 2043 support. A server MUST respond to options it does not recognize with 2044 a BAD response. The client SHOULD NOT specify any option more than 2045 once; however, if the client does this, the server MUST act as if it 2046 received the option only once. The order in which options are 2047 specified by the client is not significant. 2049 In general, each selection option except RECURSIVEMATCH will have a 2050 corresponding return option. The REMOTE selection option is an 2051 anomaly in this regard, and does not have a corresponding return 2052 option. That is because it expands, rather than restricts, the set 2053 of mailboxes that are returned. Future extensions to this 2054 specification should keep parallelism in mind and define a pair of 2055 corresponding options. 2057 Server implementations are permitted to "hide" otherwise accessible 2058 mailboxes from the wildcard characters, by preventing certain 2059 characters or names from matching a wildcard in certain situations. 2060 For example, a UNIX-based server might restrict the interpretation of 2061 "*" so that an initial "/" character does not match. 2063 The special name INBOX is included in the output from LIST, if INBOX 2064 is supported by this server for this user and if the uppercase string 2065 "INBOX" matches the interpreted reference and mailbox name arguments 2066 with wildcards as described above. The criteria for omitting INBOX 2067 is whether SELECT INBOX will return failure; it is not relevant 2068 whether the user's real INBOX resides on this or some other server. 2070 6.3.9.1. LIST Selection Options 2072 The selection options defined in this specification are as follows: 2074 SUBSCRIBED - causes the LIST command to list subscribed names, 2075 rather than the existing mailboxes. This will often be a subset 2076 of the actual mailboxes. It's also possible for this list to 2077 contain the names of mailboxes that don't exist. In any case, the 2078 list MUST include exactly those mailbox names that match the 2079 canonical list pattern and are subscribed to. 2081 This option defines a mailbox attribute, "\Subscribed", that 2082 indicates that a mailbox name is subscribed to. The "\Subscribed" 2083 attribute MUST be supported and MUST be accurately computed when 2084 the SUBSCRIBED selection option is specified. 2086 Note that the SUBSCRIBED selection option implies the SUBSCRIBED 2087 return option (see below). 2089 REMOTE - causes the LIST command to show remote mailboxes as well as 2090 local ones, as described in [RFC2193]. This option is intended to 2091 replace the RLIST command and, in conjunction with the SUBSCRIBED 2092 selection option, the RLSUB command. Servers that don't support 2093 remote mailboxes just ignore this option. 2095 This option defines a mailbox attribute, "\Remote", that indicates 2096 that a mailbox is a remote mailbox. The "\Remote" attribute MUST 2097 be accurately computed when the REMOTE option is specified. 2099 The REMOTE selection option has no interaction with other options. 2100 Its effect is to tell the server to apply the other options, if 2101 any, to remote mailboxes, in addition to local ones. In 2102 particular, it has no interaction with RECURSIVEMATCH (see below). 2103 A request for (REMOTE RECURSIVEMATCH) is invalid, because a 2104 request for (RECURSIVEMATCH) is also invalid. A request for 2105 (REMOTE RECURSIVEMATCH SUBSCRIBED) is asking for all subscribed 2106 mailboxes, both local and remote. 2108 RECURSIVEMATCH - this option forces the server to return information 2109 about parent mailboxes that don't match other selection options, 2110 but have some submailboxes that do. Information about children is 2111 returned in the CHILDINFO extended data item, as described in 2112 Section 6.3.9.5. 2114 Note 1: In order for a parent mailbox to be returned, it still has 2115 to match the canonical LIST pattern. 2117 Note 2: When returning the CHILDINFO extended data item, it 2118 doesn't matter whether or not the submailbox matches the canonical 2119 LIST pattern. See also example 9 in Section 6.3.9.6. 2121 The RECURSIVEMATCH option MUST NOT occur as the only selection 2122 option (or only with REMOTE), as it only makes sense when other 2123 selection options are also used. The server MUST return BAD 2124 tagged response in such case. 2126 Note that even if the RECURSIVEMATCH option is specified, the 2127 client MUST still be able to handle a case when a CHILDINFO 2128 extended data item is returned and there are no submailboxes that 2129 meet the selection criteria of the subsequent LIST command, as 2130 they can be deleted/renamed after the LIST response was sent, but 2131 before the client had a chance to access them. 2133 6.3.9.2. LIST Return Options 2135 The return options defined in this specification are as follows: 2137 SUBSCRIBED - causes the LIST command to return subscription state 2138 for all matching mailbox names. The "\Subscribed" attribute MUST 2139 be supported and MUST be accurately computed when the SUBSCRIBED 2140 return option is specified. Further, all mailbox flags MUST be 2141 accurately computed (this differs from the behavior of the 2142 obsolete LSUB command from IMAP4rev1). 2144 CHILDREN - requests mailbox child information as originally proposed 2145 in [RFC3348]. See Section 6.3.9.4, below, for details. This 2146 option MUST be supported by all servers. 2148 6.3.9.3. General Principles for Returning LIST Responses 2150 This section outlines several principles that can be used by server 2151 implementations of this document to decide whether a LIST response 2152 should be returned, as well as how many responses and what kind of 2153 information they may contain. 2155 1. At most one LIST response should be returned for each mailbox 2156 name that matches the canonical LIST pattern. Server 2157 implementors must not assume that clients will be able to 2158 assemble mailbox attributes and other information returned in 2159 multiple LIST responses. 2161 2. There are only two reasons for including a matching mailbox name 2162 in the responses to the LIST command (note that the server is 2163 allowed to return unsolicited responses at any time, and such 2164 responses are not governed by this rule): 2166 A. The mailbox name also satisfies the selection criteria. 2168 B. The mailbox name doesn't satisfy the selection criteria, but 2169 it has at least one descendant mailbox name that satisfies 2170 the selection criteria and that doesn't match the canonical 2171 LIST pattern. 2173 For more information on this case, see the CHILDINFO extended 2174 data item described in Section 6.3.9.5. Note that the 2175 CHILDINFO extended data item can only be returned when the 2176 RECURSIVEMATCH selection option is specified. 2178 3. Attributes returned in the same LIST response must be treated 2179 additively. For example, the following response 2181 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2183 means that the "Fruit/Peach" mailbox doesn't exist, but it is 2184 subscribed. 2186 6.3.9.4. The CHILDREN Return Option 2188 The CHILDREN return option implements the Child Mailbox Extension, 2189 originally proposed by Mike Gahrns and Raymond Cheng, of Microsoft 2190 Corporation. Most of the information in this section is taken 2191 directly from their original specification [RFC3348]. The CHILDREN 2192 return option is simply an indication that the client wants this 2193 information; a server MAY provide it even if the option is not 2194 specified. 2196 Many IMAP4 clients present to the user a hierarchical view of the 2197 mailboxes that a user has access to. Rather than initially 2198 presenting to the user the entire mailbox hierarchy, it is often 2199 preferable to show to the user a collapsed outline list of the 2200 mailbox hierarchy (particularly if there is a large number of 2201 mailboxes). The user can then expand the collapsed outline hierarchy 2202 as needed. It is common to include within the collapsed hierarchy a 2203 visual clue (such as a ''+'') to indicate that there are child 2204 mailboxes under a particular mailbox. When the visual clue is 2205 clicked, the hierarchy list is expanded to show the child mailboxes. 2206 The CHILDREN return option provides a mechanism for a client to 2207 efficiently determine whether a particular mailbox has children, 2208 without issuing a LIST "" * or a LIST "" % for each mailbox name. 2209 The CHILDREN return option defines two new attributes that MUST be 2210 returned within a LIST response: \HasChildren and \HasNoChildren. 2211 Although these attributes MAY be returned in response to any LIST 2212 command, the CHILDREN return option is provided to indicate that the 2213 client particularly wants this information. If the CHILDREN return 2214 option is present, the server MUST return these attributes even if 2215 their computation is expensive. 2217 \HasChildren 2219 The presence of this attribute indicates that the mailbox has 2220 child mailboxes. A server SHOULD NOT set this attribute if 2221 there are child mailboxes and the user does not have permission 2222 to access any of them. In this case, \HasNoChildren SHOULD be 2223 used. In many cases, however, a server may not be able to 2224 efficiently compute whether a user has access to any child 2225 mailbox. Note that even though the \HasChildren attribute for a 2226 mailbox must be correct at the time of processing of the 2227 mailbox, a client must be prepared to deal with a situation when 2228 a mailbox is marked with the \HasChildren attribute, but no 2229 child mailbox appears in the response to the LIST command. This 2230 might happen, for example, due to children mailboxes being 2231 deleted or made inaccessible to the user (using access control) 2232 by another client before the server is able to list them. 2234 \HasNoChildren 2236 The presence of this attribute indicates that the mailbox has NO 2237 child mailboxes that are accessible to the currently 2238 authenticated user. 2240 It is an error for the server to return both a \HasChildren and a 2241 \HasNoChildren attribute in the same LIST response. 2243 Note: the \HasNoChildren attribute should not be confused with the 2244 the \NoInferiors attribute, which indicates that no child mailboxes 2245 exist now and none can be created in the future. 2247 6.3.9.5. CHILDINFO Extended Data Item 2249 The CHILDINFO extended data item MUST NOT be returned unless the 2250 client has specified the RECURSIVEMATCH selection option. 2252 The CHILDINFO extended data item in a LIST response describes the 2253 selection criteria that has caused it to be returned and indicates 2254 that the mailbox has at least one descendant mailbox that matches the 2255 selection criteria. 2257 Note: Some servers allow for mailboxes to exist without requiring 2258 their parent to exist. For example, a mailbox "Customers/ABC" can 2259 exist while the mailbox "Customers" does not. As CHILDINFO extended 2260 data item is not allowed if the RECURSIVEMATCH selection option is 2261 not specified, such servers SHOULD use the "\NonExistent 2262 \HasChildren" attribute pair to signal to the client that there is a 2263 descendant mailbox that matches the selection criteria. See example 2264 11 in Section 6.3.9.6. 2266 The returned selection criteria allow the client to distinguish a 2267 solicited response from an unsolicited one, as well as to distinguish 2268 among solicited responses caused by multiple pipelined LIST commands 2269 that specify different criteria. 2271 Servers SHOULD ONLY return a non-matching mailbox name along with 2272 CHILDINFO if at least one matching child is not also being returned. 2273 That is, servers SHOULD suppress redundant CHILDINFO responses. 2275 Examples 8 and 10 in Section 6.3.9.6 demonstrate the difference 2276 between present CHILDINFO extended data item and the "\HasChildren" 2277 attribute. 2279 The following table summarizes interaction between the "\NonExistent" 2280 attribute and CHILDINFO (the first column indicates whether the 2281 parent mailbox exists): 2283 +--------+--------------+--------------------+----------------------+ 2284 | exists | meets the | has a child that | returned LIST- | 2285 | | selection | meets the | EXTENDED attributes | 2286 | | criteria | selection criteria | and CHILDINFO | 2287 +--------+--------------+--------------------+----------------------+ 2288 | no | no | no | no LIST response | 2289 | | | | returned | 2290 | yes | no | no | no LIST response | 2291 | | | | returned | 2292 | no | yes | no | (\NonExistent | 2293 | | | | ) | 2294 | yes | yes | no | () | 2295 | no | no | yes | (\NonExistent) + | 2296 | | | | CHILDINFO | 2297 | yes | no | yes | () + CHILDINFO | 2298 | no | yes | yes | (\NonExistent | 2299 | | | | ) + CHILDINFO | 2300 | yes | yes | yes | () + CHILDINFO | 2301 +--------+--------------+--------------------+----------------------+ 2303 where is one or more attributes that correspond to the 2304 selection criteria; for example, for the SUBSCRIBED option the 2305 is \Subscribed. 2307 6.3.9.6. LIST Command Examples 2309 This example shows some uses of the basic LIST command: 2311 Example: C: A101 LIST "" "" 2312 S: * LIST (\Noselect) "/" "" 2313 S: A101 OK LIST Completed 2314 C: A102 LIST #news.comp.mail.misc "" 2315 S: * LIST (\Noselect) "." #news. 2316 S: A102 OK LIST Completed 2317 C: A103 LIST /usr/staff/jones "" 2318 S: * LIST (\Noselect) "/" / 2319 S: A103 OK LIST Completed 2320 C: A202 LIST ~/Mail/ % 2321 S: * LIST (\Noselect) "/" ~/Mail/foo 2322 S: * LIST () "/" ~/Mail/meetings 2323 S: A202 OK LIST completed 2325 Extended examples: 2327 1: The first example shows the complete local hierarchy that will 2328 be used for the other examples. 2330 C: A01 LIST "" "*" 2331 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2332 S: * LIST () "/" "Fruit" 2333 S: * LIST () "/" "Fruit/Apple" 2334 S: * LIST () "/" "Fruit/Banana" 2335 S: * LIST () "/" "Tofu" 2336 S: * LIST () "/" "Vegetable" 2337 S: * LIST () "/" "Vegetable/Broccoli" 2338 S: * LIST () "/" "Vegetable/Corn" 2339 S: A01 OK done 2341 2: In the next example, we will see the subscribed mailboxes. This 2342 is similar to, but not equivalent with, . Note 2343 that the mailbox called "Fruit/Peach" is subscribed to, but does 2344 not actually exist (perhaps it was deleted while still 2345 subscribed). The "Fruit" mailbox is not subscribed to, but it 2346 has two subscribed children. The "Vegetable" mailbox is 2347 subscribed and has two children; one of them is subscribed as 2348 well. 2350 C: A02 LIST (SUBSCRIBED) "" "*" 2351 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2352 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2353 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2354 S: * LIST (\Subscribed) "/" "Vegetable" 2355 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2356 S: A02 OK done 2358 3: The next example shows the use of the CHILDREN option. The 2359 client, without having to list the second level of hierarchy, 2360 now knows which of the top-level mailboxes have submailboxes 2361 (children) and which do not. Note that it's not necessary for 2362 the server to return the \HasNoChildren attribute for the inbox, 2363 because the \NoInferiors attribute already implies that, and has 2364 a stronger meaning. 2366 C: A03 LIST () "" "%" RETURN (CHILDREN) 2367 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2368 S: * LIST (\HasChildren) "/" "Fruit" 2369 S: * LIST (\HasNoChildren) "/" "Tofu" 2370 S: * LIST (\HasChildren) "/" "Vegetable" 2371 S: A03 OK done 2373 4: In this example, we see more mailboxes that reside on another 2374 server. This is similar to the command . 2376 C: A04 LIST (REMOTE) "" "%" RETURN (CHILDREN) 2377 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2378 S: * LIST (\HasChildren) "/" "Fruit" 2379 S: * LIST (\HasNoChildren) "/" "Tofu" 2380 S: * LIST (\HasChildren) "/" "Vegetable" 2381 S: * LIST (\Remote) "/" "Bread" 2382 S: * LIST (\HasChildren \Remote) "/" "Meat" 2383 S: A04 OK done 2385 5: The following example also requests the server to include 2386 mailboxes that reside on another server. The server returns 2387 information about all mailboxes that are subscribed. This is 2388 similar to the command . We also see the use of 2389 two selection options. 2391 C: A05 LIST (REMOTE SUBSCRIBED) "" "*" 2392 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2393 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2394 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2395 S: * LIST (\Subscribed) "/" "Vegetable" 2396 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2397 S: * LIST (\Remote \Subscribed) "/" "Bread" 2398 S: A05 OK done 2400 6: The following example requests the server to include mailboxes 2401 that reside on another server. The server is asked to return 2402 subscription information for all returned mailboxes. This is 2403 different from the example above. 2405 Note that the output of this command is not a superset of the 2406 output in the previous example, as it doesn't include LIST 2407 response for the non-existent "Fruit/Peach". 2409 C: A06 LIST (REMOTE) "" "*" RETURN (SUBSCRIBED) 2410 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2411 S: * LIST () "/" "Fruit" 2412 S: * LIST () "/" "Fruit/Apple" 2413 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2414 S: * LIST () "/" "Tofu" 2415 S: * LIST (\Subscribed) "/" "Vegetable" 2416 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2417 S: * LIST () "/" "Vegetable/Corn" 2418 S: * LIST (\Remote \Subscribed) "/" "Bread" 2419 S: * LIST (\Remote) "/" "Meat" 2420 S: A06 OK done 2422 7: In the following example, the client has specified multiple 2423 mailbox patterns. Note that this example does not use the 2424 mailbox hierarchy used in the previous examples. 2426 C: BBB LIST "" ("INBOX" "Drafts" "Sent/%") 2427 S: * LIST () "/" "INBOX" 2428 S: * LIST (\NoInferiors) "/" "Drafts" 2429 S: * LIST () "/" "Sent/March2004" 2430 S: * LIST (\Marked) "/" "Sent/December2003" 2431 S: * LIST () "/" "Sent/August2004" 2432 S: BBB OK done 2434 8: The following example demonstrates the difference between the 2435 \HasChildren attribute and the CHILDINFO extended data item. 2437 Let's assume there is the following hierarchy: 2439 C: C01 LIST "" "*" 2440 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2441 S: * LIST () "/" "Foo" 2442 S: * LIST () "/" "Foo/Bar" 2443 S: * LIST () "/" "Foo/Baz" 2444 S: * LIST () "/" "Moo" 2445 S: C01 OK done 2447 If the client asks RETURN (CHILDREN), it will get this: 2449 C: CA3 LIST "" "%" RETURN (CHILDREN) 2450 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2451 S: * LIST (\HasChildren) "/" "Foo" 2452 S: * LIST (\HasNoChildren) "/" "Moo" 2453 S: CA3 OK done 2455 A) Let's also assume that the mailbox "Foo/Baz" is the only 2456 subscribed mailbox. Then we get this result: 2458 C: C02 LIST (SUBSCRIBED) "" "*" 2459 S: * LIST (\Subscribed) "/" "Foo/Baz" 2460 S: C02 OK done 2462 Now, if the client issues , the server 2463 will return no mailboxes (as the mailboxes "Moo", "Foo", and 2464 "Inbox" are NOT subscribed). However, if the client issues 2465 this: 2467 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2468 S: * LIST () "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2469 S: C04 OK done 2471 (i.e., the mailbox "Foo" is not subscribed, but it has a child 2472 that is.) 2474 A1) If the mailbox "Foo" had also been subscribed, the last 2475 command would return this: 2477 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2478 S: * LIST (\Subscribed) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2479 S: C04 OK done 2481 or even this: 2483 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2484 S: * LIST (\Subscribed \HasChildren) "/" "Foo" ("CHILDINFO" 2485 ("SUBSCRIBED")) 2486 S: C04 OK done 2488 A2) If we assume instead that the mailbox "Foo" is not part of 2489 the original hierarchy and is not subscribed, the last command 2490 will give this result: 2492 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2493 S: * LIST (\NonExistent) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2494 S: C04 OK done 2495 B) Now, let's assume that no mailbox is subscribed. In this 2496 case, the command will 2497 return no responses, as there are no subscribed children (even 2498 though "Foo" has children). 2500 C) And finally, suppose that only the mailboxes "Foo" and "Moo" 2501 are subscribed. In that case, we see this result: 2503 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" RETURN (CHILDREN) 2504 S: * LIST (\HasChildren \Subscribed) "/" "Foo" 2505 S: * LIST (\HasNoChildren \Subscribed) "/" "Moo" 2506 S: C04 OK done 2508 (which means that the mailbox "Foo" has children, but none of 2509 them is subscribed). 2511 9: The following example demonstrates that the CHILDINFO extended 2512 data item is returned whether or not children mailboxes match 2513 the canonical LIST pattern. 2515 Let's assume there is the following hierarchy: 2517 C: D01 LIST "" "*" 2518 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2519 S: * LIST () "/" "foo2" 2520 S: * LIST () "/" "foo2/bar1" 2521 S: * LIST () "/" "foo2/bar2" 2522 S: * LIST () "/" "baz2" 2523 S: * LIST () "/" "baz2/bar2" 2524 S: * LIST () "/" "baz2/bar22" 2525 S: * LIST () "/" "baz2/bar222" 2526 S: * LIST () "/" "eps2" 2527 S: * LIST () "/" "eps2/mamba" 2528 S: * LIST () "/" "qux2/bar2" 2529 S: D01 OK done 2531 And that the following mailboxes are subscribed: 2533 C: D02 LIST (SUBSCRIBED) "" "*" 2534 S: * LIST (\Subscribed) "/" "foo2/bar1" 2535 S: * LIST (\Subscribed) "/" "foo2/bar2" 2536 S: * LIST (\Subscribed) "/" "baz2/bar2" 2537 S: * LIST (\Subscribed) "/" "baz2/bar22" 2538 S: * LIST (\Subscribed) "/" "baz2/bar222" 2539 S: * LIST (\Subscribed) "/" "eps2" 2540 S: * LIST (\Subscribed) "/" "eps2/mamba" 2541 S: * LIST (\Subscribed) "/" "qux2/bar2" 2542 S: D02 OK done 2543 The client issues the following command first: 2545 C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*2" 2546 S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED")) 2547 S: * LIST (\Subscribed) "/" "foo2/bar2" 2548 S: * LIST (\Subscribed) "/" "baz2/bar2" 2549 S: * LIST (\Subscribed) "/" "baz2/bar22" 2550 S: * LIST (\Subscribed) "/" "baz2/bar222" 2551 S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED")) 2552 S: * LIST (\Subscribed) "/" "qux2/bar2" 2553 S: D03 OK done 2555 and the server may also include (but this would violate a SHOULD 2556 NOT in Section 3.5, because CHILDINFO is redundant) 2558 S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED")) 2559 S: * LIST (\NonExistent) "/" "qux2" ("CHILDINFO" ("SUBSCRIBED")) 2561 The CHILDINFO extended data item is returned for mailboxes 2562 "foo2", "baz2", and "eps2", because all of them have subscribed 2563 children, even though for the mailbox "foo2" only one of the two 2564 subscribed children matches the pattern, for the mailbox "baz2" 2565 all the subscribed children match the pattern, and for the 2566 mailbox "eps2" none of the subscribed children matches the 2567 pattern. 2569 Note that if the client issues 2571 C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*" 2572 S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED")) 2573 S: * LIST (\Subscribed) "/" "foo2/bar1" 2574 S: * LIST (\Subscribed) "/" "foo2/bar2" 2575 S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED")) 2576 S: * LIST (\Subscribed) "/" "baz2/bar2" 2577 S: * LIST (\Subscribed) "/" "baz2/bar22" 2578 S: * LIST (\Subscribed) "/" "baz2/bar222" 2579 S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED")) 2580 S: * LIST (\Subscribed) "/" "eps2/mamba" 2581 S: * LIST (\Subscribed) "/" "qux2/bar2" 2582 S: D03 OK done 2584 The LIST responses for mailboxes "foo2", "baz2", and "eps2" 2585 still have the CHILDINFO extended data item, even though this 2586 information is redundant and the client can determine it by 2587 itself. 2589 10: The following example shows usage of multiple mailbox patterns. 2590 It also demonstrates that the presence of the CHILDINFO extended 2591 data item doesn't necessarily imply \HasChildren. 2593 C: a1 LIST "" ("foo" "foo/*") 2594 S: * LIST () "/" foo 2595 S: a1 OK done 2597 C: a2 LIST (SUBSCRIBED) "" "foo/*" 2598 S: * LIST (\Subscribed \NonExistent) "/" foo/bar 2599 S: a2 OK done 2601 C: a3 LIST (SUBSCRIBED RECURSIVEMATCH) "" foo RETURN (CHILDREN) 2602 S: * LIST (\HasNoChildren) "/" foo ("CHILDINFO" ("SUBSCRIBED")) 2603 S: a3 OK done 2605 11: The following example shows how a server that supports missing 2606 mailbox hierarchy elements can signal to a client that didn't 2607 specify the RECURSIVEMATCH selection option that there is a 2608 child mailbox that matches the selection criteria. 2610 C: a1 LIST (REMOTE) "" * 2611 S: * LIST () "/" music/rock 2612 S: * LIST (\Remote) "/" also/jazz 2613 S: a1 OK done 2615 C: a2 LIST () "" % 2616 S: * LIST (\NonExistent \HasChildren) "/" music 2617 S: a2 OK done 2619 C: a3 LIST (REMOTE) "" % 2620 S: * LIST (\NonExistent \HasChildren) "/" music 2621 S: * LIST (\NonExistent \HasChildren) "/" also 2622 S: a3 OK done 2624 C: a3.1 LIST "" (% music/rock) 2625 S: * LIST () "/" music/rock 2626 S: a3.1 OK done 2628 Because "music/rock" is the only mailbox under "music", there's 2629 no need for the server to also return "music". However clients 2630 must handle both cases. 2632 6.3.10. NAMESPACE Command 2634 Arguments: none 2636 Responses: REQUIRED untagged responses: NAMESPACE 2637 Result: OK - command completed 2638 NO - Can't complete the command 2639 BAD - arguments invalid 2641 The NAMESPACE command causes a single ungagged NAMESPACE response to 2642 be returned. The untagged NAMESPACE response contains the prefix and 2643 hierarchy delimiter to the server's Personal Namespace(s), Other 2644 Users' Namespace(s), and Shared Namespace(s) that the server wishes 2645 to expose. The response will contain a NIL for any namespace class 2646 that is not available. Namespace-Response-Extensions ABNF non 2647 terminal is defined for extensibility and MAY be included in the 2648 response. Namespace-Response-Extensions which are not on the IETF 2649 standards track, MUST be prefixed with an "X-". 2651 Example 1: 2653 In this example a server supports a single personal namespace. No 2654 leading prefix is used on personal mailboxes and "/" is the hierarchy 2655 delimiter. 2657 C: A001 NAMESPACE 2658 S: * NAMESPACE (("" "/")) NIL NIL 2659 S: A001 OK NAMESPACE command completed 2661 Example 2: 2663 A user logged on anonymously to a server. No personal mailboxes are 2664 associated with the anonymous user and the user does not have access 2665 to the Other Users' Namespace. No prefix is required to access 2666 shared mailboxes and the hierarchy delimiter is "." 2668 C: A001 NAMESPACE 2669 S: * NAMESPACE NIL NIL (("" ".")) 2670 S: A001 OK NAMESPACE command completed 2672 Example 3: 2674 A server that contains a Personal Namespace and a single Shared 2675 Namespace. 2677 C: A001 NAMESPACE 2678 S: * NAMESPACE (("" "/")) NIL (("Public Folders/" "/")) 2679 S: A001 OK NAMESPACE command completed 2681 Example 4: 2683 A server that contains a Personal Namespace, Other Users' Namespace 2684 and multiple Shared Namespaces. Note that the hierarchy delimiter 2685 used within each namespace can be different. 2687 C: A001 NAMESPACE 2688 S: * NAMESPACE (("" "/")) (("~" "/")) (("#shared/" "/") 2689 ("#public/" "/")("#ftp/" "/")("#news." ".")) 2690 S: A001 OK NAMESPACE command completed 2692 The prefix string allows a client to do things such as automatically 2693 creating personal mailboxes or LISTing all available mailboxes within 2694 a namespace. 2696 Example 5: 2698 A server that supports only the Personal Namespace, with a leading 2699 prefix of INBOX to personal mailboxes and a hierarchy delimiter of 2700 "." 2702 C: A001 NAMESPACE 2703 S: * NAMESPACE (("INBOX." ".")) NIL NIL 2704 S: A001 OK NAMESPACE command completed 2706 < Automatically create a mailbox to store sent items.> 2708 C: A002 CREATE "INBOX.Sent Mail" 2709 S: A002 OK CREATE command completed 2711 Although typically a server will support only a single Personal 2712 Namespace, and a single Other User's Namespace, circumstances exist 2713 where there MAY be multiples of these, and a client MUST be prepared 2714 for them. If a client is configured such that it is required to 2715 create a certain mailbox, there can be circumstances where it is 2716 unclear which Personal Namespaces it should create the mailbox in. 2717 In these situations a client SHOULD let the user select which 2718 namespaces to create the mailbox in or just use the first personal 2719 namespace. 2721 Example 6: 2723 In this example, a server supports 2 Personal Namespaces. In 2724 addition to the regular Personal Namespace, the user has an 2725 additional personal namespace to allow access to mailboxes in an MH 2726 format mailstore. 2728 The client is configured to save a copy of all mail sent by the user 2729 into a mailbox called 'Sent Mail'. Furthermore, after a message is 2730 deleted from a mailbox, the client is configured to move that message 2731 to a mailbox called 'Deleted Items'. 2733 Note that this example demonstrates how some extension flags can be 2734 passed to further describe the #mh namespace. 2736 C: A001 NAMESPACE 2737 S: * NAMESPACE (("" "/")("#mh/" "/" "X-PARAM" ("FLAG1" "FLAG2"))) 2738 NIL NIL 2739 S: A001 OK NAMESPACE command completed 2741 < It is desired to keep only one copy of sent mail. It is unclear 2742 which Personal Namespace the client should use to create the 'Sent 2743 Mail' mailbox. The user is prompted to select a namespace and 2744 only one 'Sent Mail' mailbox is created. > 2746 C: A002 CREATE "Sent Mail" 2747 S: A002 OK CREATE command completed 2749 < The client is designed so that it keeps two 'Deleted Items' 2750 mailboxes, one for each namespace. > 2752 C: A003 CREATE "Delete Items" 2753 S: A003 OK CREATE command completed 2755 C: A004 CREATE "#mh/Deleted Items" 2756 S: A004 OK CREATE command completed 2758 The next level of hierarchy following the Other Users' Namespace 2759 prefix SHOULD consist of , where is a user name 2760 as per the LOGIN or AUTHENTICATE command. 2762 A client can construct a LIST command by appending a "%" to the Other 2763 Users' Namespace prefix to discover the Personal Namespaces of other 2764 users that are available to the currently authenticated user. 2766 In response to such a LIST command, a server SHOULD NOT return user 2767 names that have not granted access to their personal mailboxes to the 2768 user in question. 2770 A server MAY return a LIST response containing only the names of 2771 users that have explicitly granted access to the user in question. 2773 Alternatively, a server MAY return NO to such a LIST command, 2774 requiring that a user name be included with the Other Users' 2775 Namespace prefix before listing any other user's mailboxes. 2777 Example 7: 2779 A server that supports providing a list of other user's mailboxes 2780 that are accessible to the currently logged on user. 2782 C: A001 NAMESPACE 2783 S: * NAMESPACE (("" "/")) (("Other Users/" "/")) NIL 2784 S: A001 OK NAMESPACE command completed 2786 C: A002 LIST "" "Other Users/%" 2787 S: * LIST () "/" "Other Users/Mike" 2788 S: * LIST () "/" "Other Users/Karen" 2789 S: * LIST () "/" "Other Users/Matthew" 2790 S: * LIST () "/" "Other Users/Tesa" 2791 S: A002 OK LIST command completed 2793 Example 8: 2795 A server that does not support providing a list of other user's 2796 mailboxes that are accessible to the currently logged on user. The 2797 mailboxes are listable if the client includes the name of the other 2798 user with the Other Users' Namespace prefix. 2800 C: A001 NAMESPACE 2801 S: * NAMESPACE (("" "/")) (("#Users/" "/")) NIL 2802 S: A001 OK NAMESPACE command completed 2804 < In this example, the currently logged on user has access to the 2805 Personal Namespace of user Mike, but the server chose to suppress 2806 this information in the LIST response. However, by appending the 2807 user name Mike (received through user input) to the Other Users' 2808 Namespace prefix, the client is able to get a listing of the 2809 personal mailboxes of user Mike. > 2811 C: A002 LIST "" "#Users/%" 2812 S: A002 NO The requested item could not be found. 2814 C: A003 LIST "" "#Users/Mike/%" 2815 S: * LIST () "/" "#Users/Mike/INBOX" 2816 S: * LIST () "/" "#Users/Mike/Foo" 2817 S: A003 OK LIST command completed. 2819 A prefix string might not contain a hierarchy delimiter, because in 2820 some cases it is not needed as part of the prefix. 2822 Example 9: 2824 A server that allows access to the Other Users' Namespace by 2825 prefixing the others' mailboxes with a '~' followed by , 2826 where is a user name as per the LOGIN or AUTHENTICATE 2827 command. 2829 C: A001 NAMESPACE 2830 S: * NAMESPACE (("" "/")) (("~" "/")) NIL 2831 S: A001 OK NAMESPACE command completed 2833 < List the mailboxes for user mark > 2835 C: A002 LIST "" "~mark/%" 2836 S: * LIST () "/" "~mark/INBOX" 2837 S: * LIST () "/" "~mark/foo" 2838 S: A002 OK LIST command completed 2840 6.3.11. STATUS Command 2842 Arguments: mailbox name 2843 status data item names 2845 Responses: REQUIRED untagged responses: STATUS 2847 Result: OK - status completed 2848 NO - status failure: no status for that name 2849 BAD - command unknown or arguments invalid 2851 The STATUS command requests the status of the indicated mailbox. It 2852 does not change the currently selected mailbox, nor does it affect 2853 the state of any messages in the queried mailbox. 2855 The STATUS command provides an alternative to opening a second 2856 IMAP4rev2 connection and doing an EXAMINE command on a mailbox to 2857 query that mailbox's status without deselecting the current mailbox 2858 in the first IMAP4rev2 connection. 2860 Unlike the LIST command, the STATUS command is not guaranteed to be 2861 fast in its response. Under certain circumstances, it can be quite 2862 slow. In some implementations, the server is obliged to open the 2863 mailbox read-only internally to obtain certain status information. 2864 Also unlike the LIST command, the STATUS command does not accept 2865 wildcards. 2867 Note: The STATUS command is intended to access the status of 2868 mailboxes other than the currently selected mailbox. Because the 2869 STATUS command can cause the mailbox to be opened internally, and 2870 because this information is available by other means on the 2871 selected mailbox, the STATUS command SHOULD NOT be used on the 2872 currently selected mailbox. 2874 The STATUS command MUST NOT be used as a "check for new messages 2875 in the selected mailbox" operation (refer to sections Section 7, 2876 Section 7.3.1 for more information about the proper method for new 2877 message checking). 2879 Because the STATUS command is not guaranteed to be fast in its 2880 results, clients SHOULD NOT expect to be able to issue many 2881 consecutive STATUS commands and obtain reasonable performance. 2883 The currently defined status data items that can be requested are: 2885 MESSAGES The number of messages in the mailbox. 2887 UIDNEXT The next unique identifier value of the mailbox. Refer to 2888 Section 2.3.1.1 for more information. 2890 UIDVALIDITY The unique identifier validity value of the mailbox. 2891 Refer to Section 2.3.1.1 for more information. 2893 UNSEEN The number of messages which do not have the \Seen flag set. 2895 SIZE The total size of the mailbox in octets. This is not strictly 2896 required to be an exact value, but it MUST be equal to or greater 2897 than the sum of the values of the RFC822.SIZE FETCH message data 2898 items (see Section 6.4.5) of all messages in the mailbox. 2900 Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES) 2901 S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292) 2902 S: A042 OK STATUS completed 2904 6.3.12. APPEND Command 2906 Arguments: mailbox name 2907 OPTIONAL flag parenthesized list 2908 OPTIONAL date/time string 2909 message literal 2911 Responses: no specific responses for this command 2913 Result: OK - append completed 2914 NO - append error: can't append to that mailbox, error 2915 in flags or date/time or message text 2916 BAD - command unknown or arguments invalid 2918 The APPEND command appends the literal argument as a new message to 2919 the end of the specified destination mailbox. This argument SHOULD 2920 be in the format of an [RFC-5322] or [I18N-HDRS] message. 8-bit 2921 characters are permitted in the message. A server implementation 2922 that is unable to preserve 8-bit data properly MUST be able to 2923 reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB] 2924 content transfer encoding. 2926 Note: There may be exceptions, e.g., draft messages, in which 2927 required [RFC-5322] header lines are omitted in the message 2928 literal argument to APPEND. The full implications of doing so 2929 must be understood and carefully weighed. 2931 If a flag parenthesized list is specified, the flags SHOULD be set in 2932 the resulting message; otherwise, the flag list of the resulting 2933 message is set to empty by default. 2935 If a date-time is specified, the internal date SHOULD be set in the 2936 resulting message; otherwise, the internal date of the resulting 2937 message is set to the current date and time by default. 2939 If the append is unsuccessful for any reason, the mailbox MUST be 2940 restored to its state before the APPEND attempt; no partial appending 2941 is permitted. 2943 If the destination mailbox does not exist, a server MUST return an 2944 error, and MUST NOT automatically create the mailbox. Unless it is 2945 certain that the destination mailbox can not be created, the server 2946 MUST send the response code "[TRYCREATE]" as the prefix of the text 2947 of the tagged NO response. This gives a hint to the client that it 2948 can attempt a CREATE command and retry the APPEND if the CREATE is 2949 successful. 2951 On successful completion of an APPEND, the server SHOULD return an 2952 APPENDUID response code. 2954 In the case of a mailbox that has permissions set so that the client 2955 can APPEND to the mailbox, but not SELECT or EXAMINE it, the server 2956 SHOULD NOT send an APPENDUID response code as it would disclose 2957 information about the mailbox. 2959 In the case of a mailbox that has UIDNOTSTICKY status (see 2960 UIDNOTSTICKY response code definition), the server MAY omit the 2961 APPENDUID response code as it is not meaningful. 2963 If the server does not return the APPENDUID response codes, the 2964 client can discover this information by selecting the destination 2965 mailbox. The location of messages placed in the destination mailbox 2966 by APPEND can be determined by using FETCH and/or SEARCH commands 2967 (e.g., for Message-ID or some unique marker placed in the message in 2968 an APPEND). 2970 If the mailbox is currently selected, the normal new message actions 2971 SHOULD occur. Specifically, the server SHOULD notify the client 2972 immediately via an untagged EXISTS response. If the server does not 2973 do so, the client MAY issue a NOOP command after one or more APPEND 2974 commands. 2976 Example: C: A003 APPEND saved-messages (\Seen) {310} 2977 S: + Ready for literal data 2978 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) 2979 C: From: Fred Foobar 2980 C: Subject: afternoon meeting 2981 C: To: mooch@owatagu.siam.edu 2982 C: Message-Id: 2983 C: MIME-Version: 1.0 2984 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 2985 C: 2986 C: Hello Joe, do you think we can meet at 3:30 tomorrow? 2987 C: 2988 S: A003 OK APPEND completed 2990 Example: C: A003 APPEND saved-messages (\Seen) {297} 2991 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) 2992 C: From: Fred Foobar 2993 C: Subject: afternoon meeting 2994 C: To: mooch@example.com 2995 C: Message-Id: 2996 C: MIME-Version: 1.0 2997 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 2998 C: 2999 C: Hello Joe, do you think we can meet at 3:30 tomorrow? 3000 C: 3001 S: A003 OK [APPENDUID 38505 3955] APPEND completed 3002 C: A004 COPY 2:4 meeting 3003 S: A004 OK [COPYUID 38505 304,319:320 3956:3958] Done 3004 C: A005 UID COPY 305:310 meeting 3005 S: A005 OK No matching messages, so nothing copied 3006 C: A006 COPY 2 funny 3007 S: A006 OK Done 3008 C: A007 SELECT funny 3009 S: * 1 EXISTS 3010 S: * OK [UIDVALIDITY 3857529045] Validity session-only 3011 S: * OK [UIDNEXT 2] Predicted next UID 3012 S: * NO [UIDNOTSTICKY] Non-persistent UIDs 3013 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 3014 S: * OK [PERMANENTFLAGS (\Deleted \Seen)] Limited 3015 S: A007 OK [READ-WRITE] SELECT completed 3017 In this example, A003 and A004 demonstrate successful appending and 3018 copying to a mailbox that returns the UIDs assigned to the messages. 3019 A005 is an example in which no messages were copied; this is because 3020 in A003, we see that message 2 had UID 304, and message 3 had UID 3021 319; therefore, UIDs 305 through 310 do not exist (refer to 3022 Section 2.3.1.1 for further explanation). A006 is an example of a 3023 message being copied that did not return a COPYUID; and, as expected, 3024 A007 shows that the mail store containing that mailbox does not 3025 support persistent UIDs. 3027 Note: The APPEND command is not used for message delivery, because 3028 it does not provide a mechanism to transfer [SMTP] envelope 3029 information. 3031 6.3.13. IDLE Command 3033 Arguments: none 3035 Responses: continuation data will be requested; the client sends the 3036 continuation data "DONE" to end the command 3038 Result: OK - IDLE completed after client sent "DONE" 3039 NO - failure: the server will not allow the IDLE command 3040 at this time 3041 BAD - command unknown or arguments invalid 3043 Without the IDLE command a client requires to poll the server for 3044 changes to the selected mailbox (new mail, deletions, flag changes). 3045 It's often more desirable to have the server transmit updates to the 3046 client in real time. This allows a user to see new mail immediately. 3047 The IDLE command allows a client to tell the server that it's ready 3048 to accept such real-time updates. 3050 The IDLE command is sent from the client to the server when the 3051 client is ready to accept unsolicited mailbox update messages. The 3052 server requests a response to the IDLE command using the continuation 3053 ("+") response. The IDLE command remains active until the client 3054 responds to the continuation, and as long as an IDLE command is 3055 active, the server is now free to send untagged EXISTS, EXPUNGE, 3056 FETCH, and other responses at any time. If the server choose to send 3057 unsolicited FETCH responses, they MUST include UID FETCH item. 3059 The IDLE command is terminated by the receipt of a "DONE" 3060 continuation from the client; such response satisfies the server's 3061 continuation request. At that point, the server MAY send any 3062 remaining queued untagged responses and then MUST immediately send 3063 the tagged response to the IDLE command and prepare to process other 3064 commands. As for other commands, the processing of any new command 3065 may cause the sending of unsolicited untagged responses, subject to 3066 the ambiguity limitations. The client MUST NOT send a command while 3067 the server is waiting for the DONE, since the server will not be able 3068 to distinguish a command from a continuation. 3070 The server MAY consider a client inactive if it has an IDLE command 3071 running, and if such a server has an inactivity timeout it MAY log 3072 the client off implicitly at the end of its timeout period. Because 3073 of that, clients using IDLE are advised to terminate the IDLE and re- 3074 issue it at least every 29 minutes to avoid being logged off. This 3075 still allows a client to receive immediate mailbox updates even 3076 though it need only "poll" at half hour intervals. 3078 Example: C: A001 SELECT INBOX 3079 S: * FLAGS (\Deleted \Seen \Flagged) 3080 S: * OK [PERMANENTFLAGS (\Deleted \Seen \Flagged)] Limited 3081 S: * 3 EXISTS 3082 S: * OK [UIDVALIDITY 1] 3083 S: A001 OK [READ-WRITE] SELECT completed 3084 C: A002 IDLE 3085 S: + idling 3086 ...time passes; new mail arrives... 3087 S: * 4 EXISTS 3088 C: DONE 3089 S: A002 OK IDLE terminated 3090 ...another client expunges message 2 now... 3091 C: A003 FETCH 4 ALL 3092 S: * 4 FETCH (...) 3093 S: A003 OK FETCH completed 3094 C: A004 IDLE 3095 S: * 2 EXPUNGE 3096 S: * 3 EXISTS 3097 S: + idling 3098 ...time passes; another client expunges message 3... 3099 S: * 3 EXPUNGE 3100 S: * 2 EXISTS 3101 ...time passes; new mail arrives... 3102 S: * 3 EXISTS 3103 C: DONE 3104 S: A004 OK IDLE terminated 3105 C: A005 FETCH 3 ALL 3106 S: * 3 FETCH (...) 3107 S: A005 OK FETCH completed 3108 C: A006 IDLE 3110 6.4. Client Commands - Selected State 3112 In the selected state, commands that manipulate messages in a mailbox 3113 are permitted. 3115 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 3116 and the authenticated state commands (SELECT, EXAMINE, NAMESPACE, 3117 CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, STATUS, and 3118 APPEND), the following commands are valid in the selected state: 3119 CLOSE, UNSELECT, EXPUNGE, SEARCH, FETCH, STORE, COPY, MOVE, and UID. 3121 6.4.1. CLOSE Command 3123 Arguments: none 3125 Responses: no specific responses for this command 3127 Result: OK - close completed, now in authenticated state 3128 BAD - command unknown or arguments invalid 3130 The CLOSE command permanently removes all messages that have the 3131 \Deleted flag set from the currently selected mailbox, and returns to 3132 the authenticated state from the selected state. No untagged EXPUNGE 3133 responses are sent. 3135 No messages are removed, and no error is given, if the mailbox is 3136 selected by an EXAMINE command or is otherwise selected read-only. 3138 Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT command 3139 MAY be issued without previously issuing a CLOSE command. The 3140 SELECT, EXAMINE, and LOGOUT commands implicitly close the currently 3141 selected mailbox without doing an expunge. However, when many 3142 messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT sequence is 3143 considerably faster than an EXPUNGE-LOGOUT or EXPUNGE-SELECT because 3144 no untagged EXPUNGE responses (which the client would probably 3145 ignore) are sent. 3147 Example: C: A341 CLOSE 3148 S: A341 OK CLOSE completed 3150 6.4.2. UNSELECT Command 3152 Arguments: none 3154 Responses: no specific responses for this command 3156 Result: OK - unselect completed, now in authenticated state 3157 BAD - no mailbox selected, or argument supplied but none 3158 permitted 3160 The UNSELECT command frees server's resources associated with the 3161 selected mailbox and returns the server to the authenticated state. 3162 This command performs the same actions as CLOSE, except that no 3163 messages are permanently removed from the currently selected mailbox. 3165 Example: C: A342 UNSELECT 3166 S: A342 OK Unselect completed 3168 6.4.3. EXPUNGE Command 3170 Arguments: none 3172 Responses: untagged responses: EXPUNGE 3174 Result: OK - expunge completed 3175 NO - expunge failure: can't expunge (e.g., permission 3176 denied) 3177 BAD - command unknown or arguments invalid 3179 The EXPUNGE command permanently removes all messages that have the 3180 \Deleted flag set from the currently selected mailbox. Before 3181 returning an OK to the client, an untagged EXPUNGE response is sent 3182 for each message that is removed. 3184 Example: C: A202 EXPUNGE 3185 S: * 3 EXPUNGE 3186 S: * 3 EXPUNGE 3187 S: * 5 EXPUNGE 3188 S: * 8 EXPUNGE 3189 S: A202 OK EXPUNGE completed 3191 Note: In this example, messages 3, 4, 7, and 11 had the \Deleted flag 3192 set. See the description of the EXPUNGE response for further 3193 explanation. 3195 6.4.4. SEARCH Command 3197 Arguments: OPTIONAL result specifier 3198 OPTIONAL [CHARSET] specification 3199 searching criteria (one or more) 3201 Responses: REQUIRED untagged response: ESEARCH 3203 Result: OK - search completed 3204 NO - search error: can't search that [CHARSET] or 3205 criteria 3206 BAD - command unknown or arguments invalid 3208 The SEARCH command searches the mailbox for messages that match the 3209 given searching criteria. 3211 The SEARCH command may contain result options. Result options 3212 control what kind of information is returned about messages matching 3213 the search criteria in an untagged ESEARCH response. If no result 3214 option is specified or empty list of options is specified "()", ALL 3215 is assumed (see below). The order of individual options is 3216 arbitrary. Individual options may contain parameters enclosed in 3217 parentheses (*). If an option has parameters, they consist of atoms 3218 and/or strings and/or lists in a specific order. Any options not 3219 defined by extensions that the server supports must be rejected with 3220 a BAD response. 3222 (*) - if an option has a mandatory parameter, which can always be 3223 represented as a number or a sequence-set, the option parameter does 3224 not need the enclosing (). See ABNF for more details. 3226 This document specifies the following result options: 3228 MIN 3230 Return the lowest message number/UID that satisfies the SEARCH 3231 criteria. 3233 If the SEARCH results in no matches, the server MUST NOT 3234 include the MIN result option in the ESEARCH response; however, 3235 it still MUST send the ESEARCH response. 3237 MAX 3239 Return the highest message number/UID that satisfies the SEARCH 3240 criteria. 3242 If the SEARCH results in no matches, the server MUST NOT 3243 include the MAX result option in the ESEARCH response; however, 3244 it still MUST send the ESEARCH response. 3246 ALL 3248 Return all message numbers/UIDs that satisfy the SEARCH 3249 criteria using the sequence-set syntax. Note, the client MUST 3250 NOT assume that messages/UIDs will be listed in any particular 3251 order. 3253 If the SEARCH results in no matches, the server MUST NOT 3254 include the ALL result option in the ESEARCH response; however, 3255 it still MUST send the ESEARCH response. 3257 COUNT Return number of the messages that satisfy the SEARCH 3258 criteria. This result option MUST always be included in the 3259 ESEARCH response. 3261 Note: future extensions to this document can allow servers to return 3262 multiple ESEARCH responses for a single extended SEARCH command. 3263 However all options specified above MUST result in a single ESEARCH 3264 response. These extensions will have to describe how results from 3265 multiple ESEARCH responses are to be amalgamated. 3267 Searching criteria consist of one or more search keys. 3269 When multiple keys are specified, the result is the intersection (AND 3270 function) of all the messages that match those keys. For example, 3271 the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers to all 3272 deleted messages from Smith that were placed in the mailbox since 3273 February 1, 1994. A search key can also be a parenthesized list of 3274 one or more search keys (e.g., for use with the OR and NOT keys). 3276 Server implementations MAY exclude [MIME-IMB] body parts with 3277 terminal content media types other than TEXT and MESSAGE from 3278 consideration in SEARCH matching. 3280 The OPTIONAL [CHARSET] specification consists of the word "CHARSET" 3281 followed by a registered [CHARSET]. It indicates the [CHARSET] of 3282 the strings that appear in the search criteria. [MIME-IMB] content 3283 transfer encodings, and [MIME-HDRS] strings in [RFC-5322]/[MIME-IMB] 3284 headers, MUST be decoded before comparing text. US-ASCII and UTF-8 3285 charsets MUST be supported; other [CHARSET]s MAY be supported. If 3286 "CHARSET" is not provided, an IMAP4rev2 server MUST assume UTF-8. 3288 If the server does not support the specified [CHARSET], it MUST 3289 return a tagged NO response (not a BAD). This response SHOULD 3290 contain the BADCHARSET response code, which MAY list the [CHARSET]s 3291 supported by the server. 3293 In all search keys that use strings, a message matches the key if the 3294 string is a substring of the associated text. The matching SHOULD be 3295 case-insensitive for characters within ASCII range. Consider using 3296 [IMAP-I18N] for language-sensitive case-insensitive searching. Note 3297 that the empty string is a substring; this is useful when doing a 3298 HEADER search in order to test for a header field presence in the 3299 message. 3301 The defined search keys are as follows. Refer to the Formal Syntax 3302 section for the precise syntactic definitions of the arguments. 3304 Messages with message sequence numbers corresponding 3305 to the specified message sequence number set. 3307 ALL All messages in the mailbox; the default initial key for ANDing. 3309 ANSWERED Messages with the \Answered flag set. 3311 BCC Messages that contain the specified string in the 3312 envelope structure's BCC field. 3314 BEFORE Messages whose internal date (disregarding time and 3315 timezone) is earlier than the specified date. 3317 BODY Messages that contain the specified string in the body 3318 of the message. Unlike TEXT (see below), this doesn't match any 3319 header fields. 3321 CC Messages that contain the specified string in the 3322 envelope structure's CC field. 3324 DELETED Messages with the \Deleted flag set. 3326 DRAFT Messages with the \Draft flag set. 3328 FLAGGED Messages with the \Flagged flag set. 3330 FROM Messages that contain the specified string in the 3331 envelope structure's FROM field. 3333 HEADER Messages that have a header with the 3334 specified field-name (as defined in [RFC-5322]) and that contains 3335 the specified string in the text of the header (what comes after 3336 the colon). If the string to search is zero-length, this matches 3337 all messages that have a header line with the specified field-name 3338 regardless of the contents. 3340 KEYWORD Messages with the specified keyword flag set. 3342 LARGER Messages with an [RFC-5322] size larger than the 3343 specified number of octets. 3345 NEW [[Fix this]] Messages that have the \Recent flag set but not the 3346 \Seen flag. This is functionally equivalent to "(RECENT UNSEEN)". 3348 NOT Messages that do not match the specified search 3349 key. 3351 ON Messages whose internal date (disregarding time and 3352 timezone) is within the specified date. 3354 OR Messages that match either search 3355 key. 3357 SEEN Messages that have the \Seen flag set. 3359 SENTBEFORE Messages whose [RFC-5322] Date: header 3360 (disregarding time and timezone) is earlier than the specified 3361 date. 3363 SENTON Messages whose [RFC-5322] Date: header (disregarding 3364 time and timezone) is within the specified date. 3366 SENTSINCE Messages whose [RFC-5322] Date: header 3367 (disregarding time and timezone) is within or later than the 3368 specified date. 3370 SINCE Messages whose internal date (disregarding time and 3371 timezone) is within or later than the specified date. 3373 SMALLER Messages with an [RFC-5322] size smaller than the 3374 specified number of octets. 3376 SUBJECT Messages that contain the specified string in the 3377 envelope structure's SUBJECT field. 3379 TEXT Messages that contain the specified string in the 3380 header (including MIME header fields) or body of the message. 3382 TO Messages that contain the specified string in the 3383 envelope structure's TO field. 3385 UID Messages with unique identifiers corresponding to 3386 the specified unique identifier set. Sequence set ranges are 3387 permitted. 3389 UNANSWERED Messages that do not have the \Answered flag set. 3391 UNDELETED Messages that do not have the \Deleted flag set. 3393 UNDRAFT Messages that do not have the \Draft flag set. 3395 UNFLAGGED Messages that do not have the \Flagged flag set. 3397 UNKEYWORD Messages that do not have the specified keyword 3398 flag set. 3400 UNSEEN Messages that do not have the \Seen flag set. 3402 Example: C: A282 SEARCH RETURN (MIN COUNT) FLAGGED 3403 SINCE 1-Feb-1994 NOT FROM "Smith" 3404 S: * ESEARCH (TAG "A282") MIN 2 COUNT 3 3405 S: A282 OK SEARCH completed 3407 Example: C: A283 SEARCH RETURN () FLAGGED 3408 SINCE 1-Feb-1994 NOT FROM "Smith" 3409 S: * ESEARCH (TAG "A283") ALL 2,10:11 3410 S: A283 OK SEARCH completed 3412 Example: C: A284 SEARCH TEXT "string not in mailbox" 3413 S: * ESEARCH (TAG "A284") 3414 S: A284 OK SEARCH completed 3415 C: A285 SEARCH CHARSET UTF-8 TEXT {6} 3416 S: + Ready for literal text 3417 C: XXXXXX 3418 S: * ESEARCH (TAG "A285") ALL 43 3419 S: A285 OK SEARCH completed 3421 Note: Since this document is restricted to 7-bit ASCII text, it is 3422 not possible to show actual UTF-8 data. The "XXXXXX" is a 3423 placeholder for what would be 6 octets of 8-bit data in an actual 3424 transaction. 3426 The following example demonstrates finding the first unseen message 3427 in the mailbox: 3429 Example: C: A284 SEARCH RETURN (MIN) UNSEEN 3430 S: * ESEARCH (TAG "A284") MIN 4 3431 S: A284 OK SEARCH completed 3433 The following example demonstrates that if the ESEARCH UID indicator 3434 is present, all data in the ESEARCH response is referring to UIDs; 3435 for example, the MIN result specifier will be followed by a UID. 3437 Example: C: A285 UID SEARCH RETURN (MIN MAX) 1:5000 3438 S: * ESEARCH (TAG "A285") UID MIN 7 MAX 3800 3439 S: A285 OK SEARCH completed 3441 The following example demonstrates returning the number of deleted 3442 messages: 3444 Example: C: A286 SEARCH RETURN (COUNT) DELETED 3445 S: * ESEARCH (TAG "A286") COUNT 15 3446 S: A286 OK SEARCH completed 3448 6.4.5. FETCH Command 3450 Arguments: sequence set 3451 message data item names or macro 3453 Responses: untagged responses: FETCH 3455 Result: OK - fetch completed 3456 NO - fetch error: can't fetch that data 3457 BAD - command unknown or arguments invalid 3459 The FETCH command retrieves data associated with a message in the 3460 mailbox. The data items to be fetched can be either a single atom or 3461 a parenthesized list. 3463 Most data items, identified in the formal syntax under the msg-att- 3464 static rule, are static and MUST NOT change for any particular 3465 message. Other data items, identified in the formal syntax under the 3466 msg-att-dynamic rule, MAY change, either as a result of a STORE 3467 command or due to external events. 3469 For example, if a client receives an ENVELOPE for a message when 3470 it already knows the envelope, it can safely ignore the newly 3471 transmitted envelope. 3473 There are three macros which specify commonly-used sets of data 3474 items, and can be used instead of data items. A macro must be used 3475 by itself, and not in conjunction with other macros or data items. 3477 ALL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE) 3479 FAST Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE) 3481 FULL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE 3482 BODY) 3484 The currently defined data items that can be fetched are: 3486 BINARY[]<> 3488 Requests that the specified section be transmitted after 3489 performing Content-Transfer-Encoding-related decoding. 3491 The argument, if present, requests that a subset of 3492 the data be returned. The semantics of a partial FETCH BINARY 3493 command are the same as for a partial FETCH BODY command, with 3494 the exception that the arguments refer to the DECODED 3495 section data. 3497 BINARY.PEEK[]<> An alternate form of 3498 BINARY[] that does not implicitly set the \Seen 3499 flag. 3501 BINARY.SIZE[] 3503 Requests the decoded size of the section (i.e., the size to 3504 expect in response to the corresponding FETCH BINARY request). 3506 Note: client authors are cautioned that this might be an 3507 expensive operation for some server implementations. 3508 Needlessly issuing this request could result in degraded 3509 performance due to servers having to calculate the value every 3510 time the request is issued. 3512 BODY Non-extensible form of BODYSTRUCTURE. 3514 BODY[
]<> 3516 The text of a particular body section. The section 3517 specification is a set of zero or more part specifiers 3518 delimited by periods. A part specifier is either a part number 3519 or one of the following: HEADER, HEADER.FIELDS, 3520 HEADER.FIELDS.NOT, MIME, and TEXT. An empty section 3521 specification refers to the entire message, including the 3522 header. 3524 Every message has at least one part number. Non-[MIME-IMB] 3525 messages, and non-multipart [MIME-IMB] messages with no 3526 encapsulated message, only have a part 1. 3528 Multipart messages are assigned consecutive part numbers, as 3529 they occur in the message. If a particular part is of type 3530 message or multipart, its parts MUST be indicated by a period 3531 followed by the part number within that nested multipart part. 3533 A part of type MESSAGE/RFC822 or MESSAGE/GLOBAL also has nested 3534 part numbers, referring to parts of the MESSAGE part's body. 3536 The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part 3537 specifiers can be the sole part specifier or can be prefixed by 3538 one or more numeric part specifiers, provided that the numeric 3539 part specifier refers to a part of type MESSAGE/RFC822 or 3540 MESSAGE/GLOBAL. The MIME part specifier MUST be prefixed by 3541 one or more numeric part specifiers. 3543 The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part 3544 specifiers refer to the [RFC-5322] header of the message or of 3545 an encapsulated [MIME-IMT] MESSAGE/RFC822 or MESSAGE/GLOBAL 3546 message. HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a 3547 list of field-name (as defined in [RFC-5322]) names, and return 3548 a subset of the header. The subset returned by HEADER.FIELDS 3549 contains only those header fields with a field-name that 3550 matches one of the names in the list; similarly, the subset 3551 returned by HEADER.FIELDS.NOT contains only the header fields 3552 with a non-matching field-name. The field-matching is ASCII 3553 range case-insensitive but otherwise exact. Subsetting does 3554 not exclude the [RFC-5322] delimiting blank line between the 3555 header and the body; the blank line is included in all header 3556 fetches, except in the case of a message which has no body and 3557 no blank line. 3559 The MIME part specifier refers to the [MIME-IMB] header for 3560 this part. 3562 The TEXT part specifier refers to the text body of the message, 3563 omitting the [RFC-5322] header. 3565 Here is an example of a complex message with some of its 3566 part specifiers: 3568 HEADER ([RFC-5322] header of the message) 3569 TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 3570 1 TEXT/PLAIN 3571 2 APPLICATION/OCTET-STREAM 3572 3 MESSAGE/RFC822 3573 3.HEADER ([RFC-5322] header of the message) 3574 3.TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 3575 3.1 TEXT/PLAIN 3576 3.2 APPLICATION/OCTET-STREAM 3577 4 MULTIPART/MIXED 3578 4.1 IMAGE/GIF 3579 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF) 3580 4.2 MESSAGE/RFC822 3581 4.2.HEADER ([RFC-5322] header of the message) 3582 4.2.TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 3583 4.2.1 TEXT/PLAIN 3584 4.2.2 MULTIPART/ALTERNATIVE 3585 4.2.2.1 TEXT/PLAIN 3586 4.2.2.2 TEXT/RICHTEXT 3587 It is possible to fetch a substring of the designated text. 3588 This is done by appending an open angle bracket ("<"), the 3589 octet position of the first desired octet, a period, the 3590 maximum number of octets desired, and a close angle bracket 3591 (">") to the part specifier. If the starting octet is beyond 3592 the end of the text, an empty string is returned. 3594 Any partial fetch that attempts to read beyond the end of the 3595 text is truncated as appropriate. A partial fetch that starts 3596 at octet 0 is returned as a partial fetch, even if this 3597 truncation happened. 3599 Note: This means that BODY[]<0.2048> of a 1500-octet message 3600 will return BODY[]<0> with a literal of size 1500, not 3601 BODY[]. 3603 Note: A substring fetch of a HEADER.FIELDS or 3604 HEADER.FIELDS.NOT part specifier is calculated after 3605 subsetting the header. 3607 The \Seen flag is implicitly set; if this causes the flags to 3608 change, they SHOULD be included as part of the FETCH responses. 3610 BODY.PEEK[
]<> An alternate form of BODY[
] 3611 that does not implicitly set the \Seen flag. 3613 BODYSTRUCTURE The [MIME-IMB] body structure of the message. This is 3614 computed by the server by parsing the [MIME-IMB] header fields in 3615 the [RFC-5322] header and [MIME-IMB] headers. 3617 ENVELOPE The envelope structure of the message. This is computed by 3618 the server by parsing the [RFC-5322] header into the component 3619 parts, defaulting various fields as necessary. 3621 FLAGS The flags that are set for this message. 3623 INTERNALDATE The internal date of the message. 3625 RFC822 Functionally equivalent to BODY[], differing in the syntax of 3626 the resulting untagged FETCH data (RFC822 is returned). This 3627 FETCH item is deprecated and will be removed in the next revision 3628 of this document. 3630 RFC822.HEADER Functionally equivalent to BODY.PEEK[HEADER], 3631 differing in the syntax of the resulting untagged FETCH data 3632 (RFC822.HEADER is returned). This FETCH item is deprecated and 3633 will be removed in the next revision of this document. 3635 RFC822.SIZE The [RFC-5322] size of the message. 3637 RFC822.TEXT Functionally equivalent to BODY[TEXT], differing in the 3638 syntax of the resulting untagged FETCH data (RFC822.TEXT is 3639 returned). This FETCH item is deprecated and will be removed in 3640 the next revision of this document. 3642 UID The unique identifier for the message. 3644 Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)]) 3645 S: * 2 FETCH .... 3646 S: * 3 FETCH .... 3647 S: * 4 FETCH .... 3648 S: A654 OK FETCH completed 3650 6.4.6. STORE Command 3652 Arguments: sequence set 3653 message data item name 3654 value for message data item 3656 Responses: untagged responses: FETCH 3658 Result: OK - store completed 3659 NO - store error: can't store that data 3660 BAD - command unknown or arguments invalid 3662 The STORE command alters data associated with a message in the 3663 mailbox. Normally, STORE will return the updated value of the data 3664 with an untagged FETCH response. A suffix of ".SILENT" in the data 3665 item name prevents the untagged FETCH, and the server SHOULD assume 3666 that the client has determined the updated value itself or does not 3667 care about the updated value. 3669 Note: Regardless of whether or not the ".SILENT" suffix was used, 3670 the server SHOULD send an untagged FETCH response if a change to a 3671 message's flags from an external source is observed. The intent 3672 is that the status of the flags is determinate without a race 3673 condition. 3675 The currently defined data items that can be stored are: 3677 FLAGS Replace the flags for the message with the 3678 argument. The new value of the flags is returned as if a FETCH of 3679 those flags was done. 3681 FLAGS.SILENT Equivalent to FLAGS, but without returning 3682 a new value. 3684 +FLAGS Add the argument to the flags for the message. 3685 The new value of the flags is returned as if a FETCH of those 3686 flags was done. 3688 +FLAGS.SILENT Equivalent to +FLAGS, but without 3689 returning a new value. 3691 -FLAGS Remove the argument from the flags for the 3692 message. The new value of the flags is returned as if a FETCH of 3693 those flags was done. 3695 -FLAGS.SILENT Equivalent to -FLAGS, but without 3696 returning a new value. 3698 Example: C: A003 STORE 2:4 +FLAGS (\Deleted) 3699 S: * 2 FETCH (FLAGS (\Deleted \Seen)) 3700 S: * 3 FETCH (FLAGS (\Deleted)) 3701 S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen)) 3702 S: A003 OK STORE completed 3704 6.4.7. COPY Command 3706 Arguments: sequence set 3707 mailbox name 3709 Responses: no specific responses for this command 3711 Result: OK - copy completed 3712 NO - copy error: can't copy those messages or to that 3713 name 3714 BAD - command unknown or arguments invalid 3716 The COPY command copies the specified message(s) to the end of the 3717 specified destination mailbox. The flags and internal date of the 3718 message(s) SHOULD be preserved in the copy. 3720 If the destination mailbox does not exist, a server SHOULD return an 3721 error. It SHOULD NOT automatically create the mailbox. Unless it is 3722 certain that the destination mailbox can not be created, the server 3723 MUST send the response code "[TRYCREATE]" as the prefix of the text 3724 of the tagged NO response. This gives a hint to the client that it 3725 can attempt a CREATE command and retry the COPY if the CREATE is 3726 successful. 3728 If the COPY command is unsuccessful for any reason, server 3729 implementations MUST restore the destination mailbox to its state 3730 before the COPY attempt. 3732 On successful completion of a COPY, the server SHOULD return a 3733 COPYUID response code. 3735 In the case of a mailbox that has permissions set so that the client 3736 can COPY to the mailbox, but not SELECT or EXAMINE it, the server 3737 SHOULD NOT send an COPYUID response code as it would disclose 3738 information about the mailbox. 3740 In the case of a mailbox that has UIDNOTSTICKY status (see the 3741 UIDNOTSTICKY response code), the server MAY omit the COPYUID response 3742 code as it is not meaningful. 3744 If the server does not return the COPYUID response code, the client 3745 can discover this information by selecting the destination mailbox. 3746 The location of messages placed in the destination mailbox by COPY 3747 can be determined by using FETCH and/or SEARCH commands (e.g., for 3748 Message-ID). 3750 Example: C: A003 COPY 2:4 MEETING 3751 S: A003 OK COPY completed 3753 6.4.8. MOVE Command 3755 Arguments: sequence set 3756 mailbox name 3758 Responses: no specific responses for this command 3760 Result: OK - move completed 3761 NO - move error: can't move those messages or to that 3762 name 3763 BAD - command unknown or arguments invalid 3765 The MOVE command moves the specified message(s) to the end of the 3766 specified destination mailbox. The flags and internal date of the 3767 message(s) SHOULD be preserved. 3769 This means that a new message is created in the target mailbox with a 3770 new UID, the original message is removed from the source mailbox, and 3771 it appears to the client as a single action. This has the same 3772 effect for each message as this sequence: 3774 1. [UID] COPY 3776 2. [UID] STORE +FLAGS.SILENT \DELETED 3778 3. UID EXPUNGE 3779 Although the effect of the MOVE is the same as the preceding steps, 3780 the semantics are not identical: The intermediate states produced by 3781 those steps do not occur, and the response codes are different. In 3782 particular, though the COPY and EXPUNGE response codes will be 3783 returned, response codes for a STORE MUST NOT be generated and the 3784 \Deleted flag MUST NOT be set for any message. 3786 Because a MOVE applies to a set of messages, it might fail partway 3787 through the set. Regardless of whether the command is successful in 3788 moving the entire set, each individual message SHOULD either be moved 3789 or unaffected. The server MUST leave each message in a state where 3790 it is in at least one of the source or target mailboxes (no message 3791 can be lost or orphaned). The server SHOULD NOT leave any message in 3792 both mailboxes (it would be bad for a partial failure to result in a 3793 bunch of duplicate messages). This is true even if the server 3794 returns a tagged NO response to the command. 3796 Because of the similarity of MOVE to COPY, extensions that affect 3797 COPY affect MOVE in the same way. Response codes such as TRYCREATE 3798 (see Section 7.1), as well as those defined by extensions, are sent 3799 as appropriate. 3801 Servers SHOULD send COPYUID in response to a UID MOVE (see 3802 Section 6.4.9) command. For additional information see Section 7.1. 3804 Servers are also advised to send the COPYUID response code in an 3805 untagged OK before sending EXPUNGE or moved responses. (Sending 3806 COPYUID in the tagged OK, as described in the UIDPLUS specification, 3807 means that clients first receive an EXPUNGE for a message and 3808 afterwards COPYUID for the same message. It can be unnecessarily 3809 difficult to process that sequence usefully.) 3811 An example: 3812 C: a UID MOVE 42:69 foo 3813 S: * OK [COPYUID 432432 42:69 1202:1229] 3814 S: * 22 EXPUNGE 3815 S: (more expunges) 3816 S: a OK Done 3818 Note that the server may send unrelated EXPUNGE responses as well, if 3819 any happen to have been expunged at the same time; this is normal 3820 IMAP operation. 3822 Note that moving a message to the currently selected mailbox (that 3823 is, where the source and target mailboxes are the same) is allowed 3824 when copying the message to the currently selected mailbox is 3825 allowed. 3827 The server may send EXPUNGE responses before the tagged response, so 3828 the client cannot safely send more commands with message sequence 3829 number arguments while the server is processing MOVE. 3831 MOVE and UID MOVE can be pipelined with other commands, but care has 3832 to be taken. Both commands modify sequence numbers and also allow 3833 unrelated EXPUNGE responses. The renumbering of other messages in 3834 the source mailbox following any EXPUNGE response can be surprising 3835 and makes it unsafe to pipeline any command that relies on message 3836 sequence numbers after a MOVE or UID MOVE. Similarly, MOVE cannot be 3837 pipelined with a command that might cause message renumbering. See 3838 Section 5.5, for more information about ambiguities as well as 3839 handling requirements for both clients and servers. 3841 6.4.9. UID Command 3843 Arguments: command name 3844 command arguments 3846 Responses: untagged responses: FETCH, ESEARCH, EXPUNGE 3848 Result: OK - UID command completed 3849 NO - UID command error 3850 BAD - command unknown or arguments invalid 3852 The UID command has three forms. In the first form, it takes as its 3853 arguments a COPY, MOVE, FETCH, or STORE command with arguments 3854 appropriate for the associated command. However, the numbers in the 3855 sequence set argument are unique identifiers instead of message 3856 sequence numbers. Sequence set ranges are permitted, but there is no 3857 guarantee that unique identifiers will be contiguous. 3859 A non-existent unique identifier is ignored without any error message 3860 generated. Thus, it is possible for a UID FETCH command to return an 3861 OK without any data or a UID COPY, UID MOVE or UID STORE to return an 3862 OK without performing any operations. 3864 In the second form, the UID command takes an EXPUNGE command with an 3865 extra parameter the specified a sequence set of UIDs to operate on. 3866 The UID EXPUNGE command permanently removes all messages that both 3867 have the \Deleted flag set and have a UID that is included in the 3868 specified sequence set from the currently selected mailbox. If a 3869 message either does not have the \Deleted flag set or has a UID that 3870 is not included in the specified sequence set, it is not affected. 3872 UID EXPUNGE is particularly useful for disconnected use clients. 3873 By using UID EXPUNGE instead of EXPUNGE when resynchronizing with 3874 the server, the client can ensure that it does not inadvertantly 3875 remove any messages that have been marked as \Deleted by other 3876 clients between the time that the client was last connected and 3877 the time the client resynchronizes. 3879 Example: C: A003 UID EXPUNGE 3000:3002 3880 S: * 3 EXPUNGE 3881 S: * 3 EXPUNGE 3882 S: * 3 EXPUNGE 3883 S: A003 OK UID EXPUNGE completed 3885 In the third form, the UID command takes a SEARCH command with SEARCH 3886 command arguments. The interpretation of the arguments is the same 3887 as with SEARCH; however, the numbers returned in a ESEARCH response 3888 for a UID SEARCH command are unique identifiers instead of message 3889 sequence numbers. Also, the corresponding ESEARCH response MUST 3890 include the UID indicator. For example, the command UID SEARCH 1:100 3891 UID 443:557 returns the unique identifiers corresponding to the 3892 intersection of two sequence sets, the message sequence number range 3893 1:100 and the UID range 443:557. 3895 Note: in the above example, the UID range 443:557 appears. The 3896 same comment about a non-existent unique identifier being ignored 3897 without any error message also applies here. Hence, even if 3898 neither UID 443 or 557 exist, this range is valid and would 3899 include an existing UID 495. 3901 Also note that a UID range of 559:* always includes the UID of the 3902 last message in the mailbox, even if 559 is higher than any 3903 assigned UID value. This is because the contents of a range are 3904 independent of the order of the range endpoints. Thus, any UID 3905 range with * as one of the endpoints indicates at least one 3906 message (the message with the highest numbered UID), unless the 3907 mailbox is empty. 3909 The number after the "*" in an untagged FETCH or EXPUNGE response is 3910 always a message sequence number, not a unique identifier, even for a 3911 UID command response. However, server implementations MUST 3912 implicitly include the UID message data item as part of any FETCH 3913 response caused by a UID command, regardless of whether a UID was 3914 specified as a message data item to the FETCH. 3916 Note: The rule about including the UID message data item as part of a 3917 FETCH response primarily applies to the UID FETCH and UID STORE 3918 commands, including a UID FETCH command that does not include UID as 3919 a message data item. Although it is unlikely that the other UID 3920 commands will cause an untagged FETCH, this rule applies to these 3921 commands as well. 3923 Example: C: A999 UID FETCH 4827313:4828442 FLAGS 3924 S: * 23 FETCH (FLAGS (\Seen) UID 4827313) 3925 S: * 24 FETCH (FLAGS (\Seen) UID 4827943) 3926 S: * 25 FETCH (FLAGS (\Seen) UID 4828442) 3927 S: A999 OK UID FETCH completed 3929 6.5. Client Commands - Experimental/Expansion 3931 6.5.1. X Command 3933 Arguments: implementation defined 3935 Responses: implementation defined 3937 Result: OK - command completed 3938 NO - failure 3939 BAD - command unknown or arguments invalid 3941 Any command prefixed with an X is an experimental command. Commands 3942 which are not part of this specification, a standard or standards- 3943 track revision of this specification, or an IESG-approved 3944 experimental protocol, MUST use the X prefix. 3946 Any added untagged responses issued by an experimental command MUST 3947 also be prefixed with an X. Server implementations MUST NOT send any 3948 such untagged responses, unless the client requested it by issuing 3949 the associated experimental command. 3951 Example: C: a441 CAPABILITY 3952 S: * CAPABILITY IMAP4rev2 XPIG-LATIN 3953 S: a441 OK CAPABILITY completed 3954 C: A442 XPIG-LATIN 3955 S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay 3956 S: A442 OK XPIG-LATIN ompleted-cay 3958 7. Server Responses 3960 Server responses are in three forms: status responses, server data, 3961 and command continuation request. The information contained in a 3962 server response, identified by "Contents:" in the response 3963 descriptions below, is described by function, not by syntax. The 3964 precise syntax of server responses is described in the Formal Syntax 3965 section. 3967 The client MUST be prepared to accept any response at all times. 3969 Status responses can be tagged or untagged. Tagged status responses 3970 indicate the completion result (OK, NO, or BAD status) of a client 3971 command, and have a tag matching the command. 3973 Some status responses, and all server data, are untagged. An 3974 untagged response is indicated by the token "*" instead of a tag. 3975 Untagged status responses indicate server greeting, or server status 3976 that does not indicate the completion of a command (for example, an 3977 impending system shutdown alert). For historical reasons, untagged 3978 server data responses are also called "unsolicited data", although 3979 strictly speaking, only unilateral server data is truly 3980 "unsolicited". 3982 Certain server data MUST be recorded by the client when it is 3983 received; this is noted in the description of that data. Such data 3984 conveys critical information which affects the interpretation of all 3985 subsequent commands and responses (e.g., updates reflecting the 3986 creation or destruction of messages). 3988 Other server data SHOULD be recorded for later reference; if the 3989 client does not need to record the data, or if recording the data has 3990 no obvious purpose (e.g., a SEARCH response when no SEARCH command is 3991 in progress), the data SHOULD be ignored. 3993 An example of unilateral untagged server data occurs when the IMAP 3994 connection is in the selected state. In the selected state, the 3995 server checks the mailbox for new messages as part of command 3996 execution. Normally, this is part of the execution of every command; 3997 hence, a NOOP command suffices to check for new messages. If new 3998 messages are found, the server sends untagged EXISTS response 3999 reflecting the new size of the mailbox. Server implementations that 4000 offer multiple simultaneous access to the same mailbox SHOULD also 4001 send appropriate unilateral untagged FETCH and EXPUNGE responses if 4002 another agent changes the state of any message flags or expunges any 4003 messages. 4005 Command continuation request responses use the token "+" instead of a 4006 tag. These responses are sent by the server to indicate acceptance 4007 of an incomplete client command and readiness for the remainder of 4008 the command. 4010 7.1. Server Responses - Status Responses 4012 Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD 4013 can be tagged or untagged. PREAUTH and BYE are always untagged. 4015 Status responses MAY include an OPTIONAL "response code". A response 4016 code consists of data inside square brackets in the form of an atom, 4017 possibly followed by a space and arguments. The response code 4018 contains additional information or status codes for client software 4019 beyond the OK/NO/BAD condition, and are defined when there is a 4020 specific action that a client can take based upon the additional 4021 information. 4023 The currently defined response codes are: 4025 ALERT The human-readable text contains a special alert that MUST be 4026 presented to the user in a fashion that calls the user's attention 4027 to the message. 4029 ALREADYEXISTS 4031 The operation attempts to create something that already exists, 4032 such as when the CREATE or RENAME directories attempt to create 4033 a mailbox and there is already one of that name. 4035 C: o RENAME this that 4036 S: o NO [ALREADYEXISTS] Mailbox "that" already exists 4038 APPENDUID 4040 Followed by the UIDVALIDITY of the destination mailbox and the 4041 UID assigned to the appended message in the destination 4042 mailbox, indicates that the message has been appended to the 4043 destination mailbox with that UID. 4045 If the server also supports the [MULTIAPPEND] extension, and if 4046 multiple messages were appended in the APPEND command, then the 4047 second value is a UID set containing the UIDs assigned to the 4048 appended messages, in the order they were transmitted in the 4049 APPEND command. This UID set may not contain extraneous UIDs 4050 or the symbol "*". 4052 Note: the UID set form of the APPENDUID response code MUST 4053 NOT be used if only a single message was appended. In 4054 particular, a server MUST NOT send a range such as 123:123. 4055 This is because a client that does not support [MULTIAPPEND] 4056 expects only a single UID and not a UID set. 4058 UIDs are assigned in strictly ascending order in the mailbox 4059 (refer to Section 2.3.1.1); note that a range of 12:10 is 4060 exactly equivalent to 10:12 and refers to the sequence 4061 10,11,12. 4063 This response code is returned in a tagged OK response to the 4064 APPEND command. 4066 AUTHENTICATIONFAILED 4068 Authentication failed for some reason on which the server is 4069 unwilling to elaborate. Typically, this includes "unknown 4070 user" and "bad password". 4072 This is the same as not sending any response code, except that 4073 when a client sees AUTHENTICATIONFAILED, it knows that the 4074 problem wasn't, e.g., UNAVAILABLE, so there's no point in 4075 trying the same login/password again later. 4077 C: b LOGIN "fred" "foo" 4078 S: b NO [AUTHENTICATIONFAILED] Authentication failed 4080 AUTHORIZATIONFAILED Authentication succeeded in using the 4081 authentication identity, but the server cannot or will not allow 4082 the authentication identity to act as the requested authorization 4083 identity. This is only applicable when the authentication and 4084 authorization identities are different. C: c1 AUTHENTICATE PLAIN 4085 [...] 4086 S: c1 NO [AUTHORIZATIONFAILED] No such authorization-ID 4087 C: c2 AUTHENTICATE PLAIN 4088 [...] 4089 S: c2 NO [AUTHORIZATIONFAILED] Authenticator is not an admin 4091 BADCHARSET Optionally followed by a parenthesized list of charsets. 4092 A SEARCH failed because the given charset is not supported by this 4093 implementation. If the optional list of charsets is given, this 4094 lists the charsets that are supported by this implementation. 4096 CANNOT 4098 The operation violates some invariant of the server and can 4099 never succeed. 4101 C: l create "///////" 4102 S: l NO [CANNOT] Adjacent slashes are not supported 4104 CAPABILITY Followed by a list of capabilities. This can appear in 4105 the initial OK or PREAUTH response to transmit an initial 4106 capabilities list. It can also appear in tagged responses to 4107 LOGIN or AUTHENTICATE commands. This makes it unnecessary for a 4108 client to send a separate CAPABILITY command if it recognizes this 4109 response. 4111 CLIENTBUG 4113 The server has detected a client bug. This can accompany all 4114 of OK, NO, and BAD, depending on what the client bug is. 4116 C: k1 select "/archive/projects/experiment-iv" 4117 [...] 4118 S: k1 OK [READ-ONLY] Done 4119 C: k2 status "/archive/projects/experiment-iv" (messages) 4120 [...] 4121 S: k2 OK [CLIENTBUG] Done 4123 CLOSED 4125 The CLOSED response code has no parameters. A server return 4126 the CLOSED response code when the currently selected mailbox is 4127 closed implicitly using the SELECT/EXAMINE command on another 4128 mailbox. The CLOSED response code serves as a boundary between 4129 responses for the previously opened mailbox (which was closed) 4130 and the newly selected mailbox; all responses before the CLOSED 4131 response code relate to the mailbox that was closed, and all 4132 subsequent responses relate to the newly opened mailbox. 4134 There is no need to return the CLOSED response code on 4135 completion of the CLOSE or the UNSELECT command (or similar), 4136 whose purpose is to close the currently selected mailbox 4137 without opening a new one. 4139 The server can also return an unsolicited CLOSED response code 4140 when it wants to force the client to return to authenticated 4141 state. For example, the server can do that when the mailbox 4142 requires repairs or is deleted in another session. 4144 CONTACTADMIN 4146 The user should contact the system administrator or support 4147 desk. 4149 C: e login "fred" "foo" 4150 S: e OK [CONTACTADMIN] 4152 COPYUID 4154 Followed by the UIDVALIDITY of the destination mailbox, a UID 4155 set containing the UIDs of the message(s) in the source mailbox 4156 that were copied to the destination mailbox and containing the 4157 UIDs assigned to the copied message(s) in the destination 4158 mailbox, indicates that the message(s) have been copied to the 4159 destination mailbox with the stated UID(s). 4161 The source UID set is in the order the message(s) were copied; 4162 the destination UID set corresponds to the source UID set and 4163 is in the same order. Neither of the UID sets may contain 4164 extraneous UIDs or the symbol "*". 4166 UIDs are assigned in strictly ascending order in the mailbox 4167 (refer to Section 2.3.1.1); note that a range of 12:10 is 4168 exactly equivalent to 10:12 and refers to the sequence 4169 10,11,12. 4171 This response code is returned in a tagged OK response to the 4172 COPY command. 4174 CORRUPTION 4176 The server discovered that some relevant data (e.g., the 4177 mailbox) are corrupt. This response code does not include any 4178 information about what's corrupt, but the server can write that 4179 to its logfiles. 4181 C: i select "/archive/projects/experiment-iv" 4182 S: i NO [CORRUPTION] Cannot open mailbox 4184 EXPIRED 4186 Either authentication succeeded or the server no longer had the 4187 necessary data; either way, access is no longer permitted using 4188 that passphrase. The client or user should get a new 4189 passphrase. 4191 C: d login "fred" "foo" 4192 S: d NO [EXPIRED] That password isn't valid any more 4194 EXPUNGEISSUED 4196 Someone else has issued an EXPUNGE for the same mailbox. The 4197 client may want to issue NOOP soon. [IMAP-MULTIACCESS] 4198 discusses this subject in depth. 4200 C: h search from fred@example.com 4201 S: * SEARCH 1 2 3 5 8 13 21 42 4202 S: h OK [EXPUNGEISSUED] Search completed 4204 INUSE 4205 An operation has not been carried out because it involves 4206 sawing off a branch someone else is sitting on. Someone else 4207 may be holding an exclusive lock needed for this operation, or 4208 the operation may involve deleting a resource someone else is 4209 using, typically a mailbox. 4211 The operation may succeed if the client tries again later. 4213 C: g delete "/archive/projects/experiment-iv" 4214 S: g NO [INUSE] Mailbox in use 4216 LIMIT 4218 The operation ran up against an implementation limit of some 4219 kind, such as the number of flags on a single message or the 4220 number of flags used in a mailbox. 4222 C: m STORE 42 FLAGS f1 f2 f3 f4 f5 ... f250 4223 S: m NO [LIMIT] At most 32 flags in one mailbox supported 4225 NONEXISTENT 4227 The operation attempts to delete something that does not exist. 4228 Similar to ALREADYEXISTS. 4230 C: p RENAME this that 4231 S: p NO [NONEXISTENT] No such mailbox 4233 NOPERM 4235 The access control system (e.g., Access Control List (ACL), see 4236 [RFC4314] does not permit this user to carry out an operation, 4237 such as selecting or creating a mailbox. 4239 C: f select "/archive/projects/experiment-iv" 4240 S: f NO [NOPERM] Access denied 4242 OVERQUOTA 4244 The user would be over quota after the operation. (The user 4245 may or may not be over quota already.) 4247 Note that if the server sends OVERQUOTA but doesn't support the 4248 IMAP QUOTA extension defined by [RFC2087], then there is a 4249 quota, but the client cannot find out what the quota is. 4251 C: n1 uid copy 1:* oldmail 4252 S: n1 NO [OVERQUOTA] Sorry 4253 C: n2 uid copy 1:* oldmail 4254 S: n2 OK [OVERQUOTA] You are now over your soft quota 4256 PARSE The human-readable text represents an error in parsing the 4257 [RFC-5322] header or [MIME-IMB] headers of a message in the 4258 mailbox. 4260 PERMANENTFLAGS Followed by a parenthesized list of flags, indicates 4261 which of the known flags the client can change permanently. Any 4262 flags that are in the FLAGS untagged response, but not the 4263 PERMANENTFLAGS list, can not be set permanently. The 4264 PERMANENTFLAGS list can also include the special flag \*, which 4265 indicates that it is possible to create new keywords by attempting 4266 to store those keywords in the mailbox. If the client attempts to 4267 STORE a flag that is not in the PERMANENTFLAGS list, the server 4268 will either ignore the change or store the state change for the 4269 remainder of the current session only. 4270 There is no need for a server that included the special flag \* to 4271 return a new PERMANENTFLAGS response code when a new keyword was 4272 successfully set on a message upon client request. However if the 4273 server has a limit on the number of different keywords that can be 4274 stored in a mailbox and that limit is reached, the server MUST 4275 send a new PERMANENTFLAGS response code without the special flag 4276 \*. 4278 PRIVACYREQUIRED 4280 The operation is not permitted due to a lack of privacy. If 4281 Transport Layer Security (TLS) is not in use, the client could 4282 try STARTTLS (see Section 6.2.1) and then repeat the operation. 4284 C: d login "fred" "foo" 4285 S: d NO [PRIVACYREQUIRED] Connection offers no privacy 4287 C: d select inbox 4288 S: d NO [PRIVACYREQUIRED] Connection offers no privacy 4290 READ-ONLY The mailbox is selected read-only, or its access while 4291 selected has changed from read-write to read-only. 4293 READ-WRITE The mailbox is selected read-write, or its access while 4294 selected has changed from read-only to read-write. 4296 SERVERBUG 4298 The server encountered a bug in itself or violated one of its 4299 own invariants. 4301 C: j select "/archive/projects/experiment-iv" 4302 S: j NO [SERVERBUG] This should not happen 4304 TRYCREATE An APPEND or COPY attempt is failing because the target 4305 mailbox does not exist (as opposed to some other reason). This is 4306 a hint to the client that the operation can succeed if the mailbox 4307 is first created by the CREATE command. 4309 UIDNEXT Followed by a decimal number, indicates the next unique 4310 identifier value. Refer to Section 2.3.1.1 for more information. 4312 UIDNOTSTICKY 4314 The selected mailbox is supported by a mail store that does not 4315 support persistent UIDs; that is, UIDVALIDITY will be different 4316 each time the mailbox is selected. Consequently, APPEND or 4317 COPY to this mailbox will not return an APPENDUID or COPYUID 4318 response code. 4320 This response code is returned in an untagged NO response to 4321 the SELECT command. 4323 Note: servers SHOULD NOT have any UIDNOTSTICKY mail stores. 4324 This facility exists to support legacy mail stores in which 4325 it is technically infeasible to support persistent UIDs. 4326 This should be avoided when designing new mail stores. 4328 UIDVALIDITY Followed by a decimal number, indicates the unique 4329 identifier validity value. Refer to Section 2.3.1.1 for more 4330 information. 4332 UNAVAILABLE 4334 Temporary failure because a subsystem is down. For example, an 4335 IMAP server that uses a Lightweight Directory Access Protocol 4336 (LDAP) or Radius server for authentication might use this 4337 response code when the LDAP/Radius server is down. 4339 C: a LOGIN "fred" "foo" 4340 S: a NO [UNAVAILABLE] User's backend down for maintenance 4342 UNKNOWN-CTE 4344 The server does not know how to decode the section's Content- 4345 Transfer-Encoding. 4347 Additional response codes defined by particular client or server 4348 implementations SHOULD be prefixed with an "X" until they are added 4349 to a revision of this protocol. Client implementations SHOULD ignore 4350 response codes that they do not recognize. 4352 7.1.1. OK Response 4354 Contents: OPTIONAL response code 4355 human-readable text 4357 The OK response indicates an information message from the server. 4358 When tagged, it indicates successful completion of the associated 4359 command. The human-readable text MAY be presented to the user as an 4360 information message. The untagged form indicates an information-only 4361 message; the nature of the information MAY be indicated by a response 4362 code. 4364 The untagged form is also used as one of three possible greetings at 4365 connection startup. It indicates that the connection is not yet 4366 authenticated and that a LOGIN or an AUTHENTICATE command is needed. 4368 Example: S: * OK IMAP4rev2 server ready 4369 C: A001 LOGIN fred blurdybloop 4370 S: * OK [ALERT] System shutdown in 10 minutes 4371 S: A001 OK LOGIN Completed 4373 7.1.2. NO Response 4375 Contents: OPTIONAL response code 4376 human-readable text 4378 The NO response indicates an operational error message from the 4379 server. When tagged, it indicates unsuccessful completion of the 4380 associated command. The untagged form indicates a warning; the 4381 command can still complete successfully. The human-readable text 4382 describes the condition. 4384 Example: C: A222 COPY 1:2 owatagusiam 4385 S: * NO Disk is 98% full, please delete unnecessary data 4386 S: A222 OK COPY completed 4387 C: A223 COPY 3:200 blurdybloop 4388 S: * NO Disk is 98% full, please delete unnecessary data 4389 S: * NO Disk is 99% full, please delete unnecessary data 4390 S: A223 NO COPY failed: disk is full 4392 7.1.3. BAD Response 4394 Contents: OPTIONAL response code 4395 human-readable text 4397 The BAD response indicates an error message from the server. When 4398 tagged, it reports a protocol-level error in the client's command; 4399 the tag indicates the command that caused the error. The untagged 4400 form indicates a protocol-level error for which the associated 4401 command can not be determined; it can also indicate an internal 4402 server failure. The human-readable text describes the condition. 4404 Example: C: ...very long command line... 4405 S: * BAD Command line too long 4406 C: ...empty line... 4407 S: * BAD Empty command line 4408 C: A443 EXPUNGE 4409 S: * BAD Disk crash, attempting salvage to a new disk! 4410 S: * OK Salvage successful, no data lost 4411 S: A443 OK Expunge completed 4413 7.1.4. PREAUTH Response 4415 Contents: OPTIONAL response code 4416 human-readable text 4418 The PREAUTH response is always untagged, and is one of three possible 4419 greetings at connection startup. It indicates that the connection 4420 has already been authenticated by external means; thus no LOGIN/ 4421 AUTHENTICATE command is needed. 4423 Example: S: * PREAUTH IMAP4rev2 server logged in as Smith 4425 7.1.5. BYE Response 4427 Contents: OPTIONAL response code 4428 human-readable text 4430 The BYE response is always untagged, and indicates that the server is 4431 about to close the connection. The human-readable text MAY be 4432 displayed to the user in a status report by the client. The BYE 4433 response is sent under one of four conditions: 4435 1. as part of a normal logout sequence. The server will close the 4436 connection after sending the tagged OK response to the LOGOUT 4437 command. 4439 2. as a panic shutdown announcement. The server closes the 4440 connection immediately. 4442 3. as an announcement of an inactivity autologout. The server 4443 closes the connection immediately. 4445 4. as one of three possible greetings at connection startup, 4446 indicating that the server is not willing to accept a connection 4447 from this client. The server closes the connection immediately. 4449 The difference between a BYE that occurs as part of a normal LOGOUT 4450 sequence (the first case) and a BYE that occurs because of a failure 4451 (the other three cases) is that the connection closes immediately in 4452 the failure case. In all cases the client SHOULD continue to read 4453 response data from the server until the connection is closed; this 4454 will ensure that any pending untagged or completion responses are 4455 read and processed. 4457 Example: S: * BYE Autologout; idle for too long 4459 7.2. Server Responses - Server and Mailbox Status 4461 These responses are always untagged. This is how server and mailbox 4462 status data are transmitted from the server to the client. Many of 4463 these responses typically result from a command with the same name. 4465 7.2.1. The ENABLED Response 4467 Contents: capability listing 4469 The ENABLED response occurs as a result of an ENABLE command. The 4470 capability listing contains a space-separated listing of capability 4471 names that the server supports and that were successfully enabled. 4472 The ENABLED response may contain no capabilities, which means that no 4473 extensions listed by the client were successfully enabled. 4475 7.2.2. CAPABILITY Response 4477 Contents: capability listing 4479 The CAPABILITY response occurs as a result of a CAPABILITY command. 4480 The capability listing contains a space-separated listing of 4481 capability names that the server supports. The capability listing 4482 MUST include the atom "IMAP4rev2". 4484 In addition, client and server implementations MUST implement the 4485 STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [PLAIN]) 4486 capabilities. See the Security Considerations section for important 4487 information. 4489 A capability name which begins with "AUTH=" indicates that the server 4490 supports that particular authentication mechanism. 4492 The LOGINDISABLED capability indicates that the LOGIN command is 4493 disabled, and that the server will respond with a tagged NO response 4494 to any attempt to use the LOGIN command even if the user name and 4495 password are valid. An IMAP client MUST NOT issue the LOGIN command 4496 if the server advertises the LOGINDISABLED capability. 4498 Other capability names indicate that the server supports an 4499 extension, revision, or amendment to the IMAP4rev2 protocol. Server 4500 responses MUST conform to this document until the client issues a 4501 command that uses the associated capability. 4503 Capability names MUST either begin with "X" or be standard or 4504 standards-track IMAP4rev2 extensions, revisions, or amendments 4505 registered with IANA. A server MUST NOT offer unregistered or non- 4506 standard capability names, unless such names are prefixed with an 4507 "X". 4509 Client implementations SHOULD NOT require any capability name other 4510 than "IMAP4rev2", and MUST ignore any unknown capability names. 4512 A server MAY send capabilities automatically, by using the CAPABILITY 4513 response code in the initial PREAUTH or OK responses, and by sending 4514 an updated CAPABILITY response code in the tagged OK response as part 4515 of a successful authentication. It is unnecessary for a client to 4516 send a separate CAPABILITY command if it recognizes these automatic 4517 capabilities. 4519 Example: S: * CAPABILITY IMAP4rev2 STARTTLS AUTH=GSSAPI XPIG-LATIN 4521 7.2.3. LIST Response 4523 Contents: name attributes 4524 hierarchy delimiter 4525 name 4527 The LIST response occurs as a result of a LIST command. It returns a 4528 single name that matches the LIST specification. There can be 4529 multiple LIST responses for a single LIST command. 4531 The following base name attributes are defined: 4533 \NonExistent The "\NonExistent" attribute indicates that a mailbox 4534 name does not refer to an existing mailbox. Note that this 4535 attribute is not meaningful by itself, as mailbox names that match 4536 the canonical LIST pattern but don't exist must not be returned 4537 unless one of the two conditions listed below is also satisfied: 4539 1. The mailbox name also satisfies the selection criteria (for 4540 example, it is subscribed and the "SUBSCRIBED" selection 4541 option has been specified). 4543 2. "RECURSIVEMATCH" has been specified, and the mailbox name has 4544 at least one descendant mailbox name that does not match the 4545 LIST pattern and does match the selection criteria. 4547 In practice, this means that the "\NonExistent" attribute is 4548 usually returned with one or more of "\Subscribed", "\Remote", 4549 "\HasChildren", or the CHILDINFO extended data item. 4551 The "\NonExistent" attribute implies "\NoSelect". 4553 \Noinferiors It is not possible for any child levels of hierarchy to 4554 exist under this name; no child levels exist now and none can be 4555 created in the future. 4557 \Noselect It is not possible to use this name as a selectable 4558 mailbox. 4560 \HasChildren The presence of this attribute indicates that the 4561 mailbox has child mailboxes. A server SHOULD NOT set this 4562 attribute if there are child mailboxes and the user does not have 4563 permission to access any of them. In this case, \HasNoChildren 4564 SHOULD be used. In many cases, however, a server may not be able 4565 to efficiently compute whether a user has access to any child 4566 mailbox. Note that even though the \HasChildren attribute for a 4567 mailbox must be correct at the time of processing of the mailbox, 4568 a client must be prepared to deal with a situation when a mailbox 4569 is marked with the \HasChildren attribute, but no child mailbox 4570 appears in the response to the LIST command. This might happen, 4571 for example, due to children mailboxes being deleted or made 4572 inaccessible to the user (using access control) by another client 4573 before the server is able to list them. 4575 \HasNoChildren The presence of this attribute indicates that the 4576 mailbox has NO child mailboxes that are accessible to the 4577 currently authenticated user. 4579 \Marked The mailbox has been marked "interesting" by the server; the 4580 mailbox probably contains messages that have been added since the 4581 last time the mailbox was selected. 4583 \Unmarked The mailbox does not contain any additional messages since 4584 the last time the mailbox was selected. 4586 \Subscribed The mailbox name was subscribed to using the SUBSCRIBE 4587 command. 4589 \Remote The mailbox is a remote mailbox. 4591 It is an error for the server to return both a \HasChildren and a 4592 \HasNoChildren attribute in the same LIST response. 4594 Note: the \HasNoChildren attribute should not be confused with the 4595 \NoInferiors attribute, which indicates that no child mailboxes 4596 exist now and none can be created in the future. 4598 If it is not feasible for the server to determine whether or not the 4599 mailbox is "interesting", the server SHOULD NOT send either \Marked 4600 or \Unmarked. The server MUST NOT send more than one of \Marked, 4601 \Unmarked, and \Noselect for a single mailbox, and MAY send none of 4602 these. 4604 In addition to the base name attributes defined above, an IMAP server 4605 MAY also include any or all of the following attributes that denote 4606 "role" (or "special-use") of a mailbox. These attributes are 4607 included along with base attributes defined above. A given mailbox 4608 may have none, one, or more than one of these attributes. In some 4609 cases, a special use is advice to a client about what to put in that 4610 mailbox. In other cases, it's advice to a client about what to 4611 expect to find there. 4613 \All This mailbox presents all messages in the user's message store. 4614 Implementations MAY omit some messages, such as, perhaps, those in 4615 \Trash and \Junk. When this special use is supported, it is 4616 almost certain to represent a virtual mailbox. 4618 \Archive This mailbox is used to archive messages. The meaning of 4619 an "archival" mailbox is server-dependent; typically, it will be 4620 used to get messages out of the inbox, or otherwise keep them out 4621 of the user's way, while still making them accessible. 4623 \Drafts This mailbox is used to hold draft messages -- typically, 4624 messages that are being composed but have not yet been sent. In 4625 some server implementations, this might be a virtual mailbox, 4626 containing messages from other mailboxes that are marked with the 4627 "\Draft" message flag. Alternatively, this might just be advice 4628 that a client put drafts here. 4630 \Flagged This mailbox presents all messages marked in some way as 4631 "important". When this special use is supported, it is likely to 4632 represent a virtual mailbox collecting messages (from other 4633 mailboxes) that are marked with the "\Flagged" message flag. 4635 \Junk This mailbox is where messages deemed to be junk mail are 4636 held. Some server implementations might put messages here 4637 automatically. Alternatively, this might just be advice to a 4638 client-side spam filter. 4640 \Sent This mailbox is used to hold copies of messages that have been 4641 sent. Some server implementations might put messages here 4642 automatically. Alternatively, this might just be advice that a 4643 client save sent messages here. 4645 \Trash This mailbox is used to hold messages that have been deleted 4646 or marked for deletion. In some server implementations, this 4647 might be a virtual mailbox, containing messages from other 4648 mailboxes that are marked with the "\Deleted" message flag. 4649 Alternatively, this might just be advice that a client that 4650 chooses not to use the IMAP "\Deleted" model should use this as 4651 its trash location. In server implementations that strictly 4652 expect the IMAP "\Deleted" model, this special use is likely not 4653 to be supported. 4655 All of special-use attributes are OPTIONAL, and any given server or 4656 message store may support any combination of the attributes, or none 4657 at all. In most cases, there will likely be at most one mailbox with 4658 a given attribute for a given user, but in some server or message 4659 store implementations it might be possible for multiple mailboxes to 4660 have the same special-use attribute. 4662 Special-use attributes are likely to be user-specific. User Adam 4663 might share his \Sent mailbox with user Barb, but that mailbox is 4664 unlikely to also serve as Barb's \Sent mailbox. 4666 The hierarchy delimiter is a character used to delimit levels of 4667 hierarchy in a mailbox name. A client can use it to create child 4668 mailboxes, and to search higher or lower levels of naming hierarchy. 4669 All children of a top-level hierarchy node MUST use the same 4670 separator character. A NIL hierarchy delimiter means that no 4671 hierarchy exists; the name is a "flat" name. 4673 The name represents an unambiguous left-to-right hierarchy, and MUST 4674 be valid for use as a reference in LIST command. Unless \Noselect or 4675 \NonExistent is indicated, the name MUST also be valid as an argument 4676 for commands, such as SELECT, that accept mailbox names. 4678 Example: S: * LIST (\Noselect) "/" ~/Mail/foo 4680 7.2.4. NAMESPACE Response 4682 Contents: the prefix and hierarchy delimiter to the server's 4683 Personal Namespace(s), Other Users' Namespace(s), and 4684 Shared Namespace(s) 4686 The NAMESPACE response occurs as a result of a NAMESPACE command. It 4687 contains the prefix and hierarchy delimiter to the server's Personal 4688 Namespace(s), Other Users' Namespace(s), and Shared Namespace(s) that 4689 the server wishes to expose. The response will contain a NIL for any 4690 namespace class that is not available. Namespace-Response-Extensions 4691 ABNF non terminal is defined for extensibility and MAY be included in 4692 the response. Namespace-Response-Extensions which are not on the 4693 IETF standards track, MUST be prefixed with an "X-". 4695 Example: S: * NAMESPACE (("" "/")) (("~" "/")) NIL 4697 7.2.5. STATUS Response 4699 Contents: name 4700 status parenthesized list 4702 The STATUS response occurs as a result of an STATUS command. It 4703 returns the mailbox name that matches the STATUS specification and 4704 the requested mailbox status information. 4706 Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292) 4708 7.2.6. ESEARCH Response 4710 Contents: one or more search-return-data pairs 4712 The ESEARCH response occurs as a result of a SEARCH or UID SEARCH 4713 command. 4715 The ESEARCH response starts with an optional search correlator. If 4716 it is missing, then the response was not caused by a particular IMAP 4717 command, whereas if it is present, it contains the tag of the command 4718 that caused the response to be returned. 4720 The search correlator is followed by an optional UID indicator. If 4721 this indicator is present, all data in the ESEARCH response refers to 4722 UIDs, otherwise all returned data refers to message numbers. 4724 The rest of the ESEARCH response contains one or more search data 4725 pairs. Each pair starts with unique return item name, followed by a 4726 space and the corresponding data. Search data pairs may be returned 4727 in any order. Unless specified otherwise by an extension, any return 4728 item name SHOULD appear only once in an ESEARCH response. 4730 [[TBD: describe the most common search data pairs returned.]] 4732 Example: S: * ESEARCH UID COUNT 5 ALL 4:19,21,28 4734 Example: S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28 4736 Example: S: * ESEARCH COUNT 5 ALL 1:17,21 4738 7.2.7. FLAGS Response 4740 Contents: flag parenthesized list 4742 The FLAGS response occurs as a result of a SELECT or EXAMINE command. 4743 The flag parenthesized list identifies the flags (at a minimum, the 4744 system-defined flags) that are applicable for this mailbox. Flags 4745 other than the system flags can also exist, depending on server 4746 implementation. 4748 The update from the FLAGS response MUST be recorded by the client. 4750 Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 4752 7.3. Server Responses - Mailbox Size 4754 These responses are always untagged. This is how changes in the size 4755 of the mailbox are transmitted from the server to the client. 4756 Immediately following the "*" token is a number that represents a 4757 message count. 4759 7.3.1. EXISTS Response 4761 Contents: none 4763 The EXISTS response reports the number of messages in the mailbox. 4764 This response occurs as a result of a SELECT or EXAMINE command, and 4765 if the size of the mailbox changes (e.g., new messages). 4767 The update from the EXISTS response MUST be recorded by the client. 4769 Example: S: * 23 EXISTS 4771 7.4. Server Responses - Message Status 4773 These responses are always untagged. This is how message data are 4774 transmitted from the server to the client, often as a result of a 4775 command with the same name. Immediately following the "*" token is a 4776 number that represents a message sequence number. 4778 7.4.1. EXPUNGE Response 4780 Contents: none 4782 The EXPUNGE response reports that the specified message sequence 4783 number has been permanently removed from the mailbox. The message 4784 sequence number for each successive message in the mailbox is 4785 immediately decremented by 1, and this decrement is reflected in 4786 message sequence numbers in subsequent responses (including other 4787 untagged EXPUNGE responses). 4789 The EXPUNGE response also decrements the number of messages in the 4790 mailbox; it is not necessary to send an EXISTS response with the new 4791 value. 4793 As a result of the immediate decrement rule, message sequence numbers 4794 that appear in a set of successive EXPUNGE responses depend upon 4795 whether the messages are removed starting from lower numbers to 4796 higher numbers, or from higher numbers to lower numbers. For 4797 example, if the last 5 messages in a 9-message mailbox are expunged, 4798 a "lower to higher" server will send five untagged EXPUNGE responses 4799 for message sequence number 5, whereas a "higher to lower server" 4800 will send successive untagged EXPUNGE responses for message sequence 4801 numbers 9, 8, 7, 6, and 5. 4803 An EXPUNGE response MUST NOT be sent when no command is in progress, 4804 nor while responding to a FETCH, STORE, or SEARCH command. This rule 4805 is necessary to prevent a loss of synchronization of message sequence 4806 numbers between client and server. A command is not "in progress" 4807 until the complete command has been received; in particular, a 4808 command is not "in progress" during the negotiation of command 4809 continuation. 4811 Note: UID FETCH, UID STORE, and UID SEARCH are different commands 4812 from FETCH, STORE, and SEARCH. An EXPUNGE response MAY be sent 4813 during a UID command. 4815 The update from the EXPUNGE response MUST be recorded by the client. 4817 Example: S: * 44 EXPUNGE 4819 7.4.2. FETCH Response 4821 Contents: message data 4823 The FETCH response returns data about a message to the client. The 4824 data are pairs of data item names and their values in parentheses. 4825 This response occurs as the result of a FETCH or STORE command, as 4826 well as by unilateral server decision (e.g., flag updates). 4828 The current data items are: 4830 BINARY[]<> 4832 An or expressing the content of the 4833 specified section after removing any Content-Transfer-Encoding- 4834 related encoding. If is present it refers to the 4835 offset within the DECODED section data. 4837 If the domain of the decoded data is "8bit" and the data does 4838 not contain the NUL octet, the server SHOULD return the data in 4839 a instead of a ; this allows the client to 4840 determine if the "8bit" data contains the NUL octet without 4841 having to explicitly scan the data stream for for NULs. 4843 Messaging clients and servers have been notoriously lax in 4844 their adherence to the Internet CRLF convention for terminating 4845 lines of textual data (text/* media types) in Internet 4846 protocols. When sending data in BINARY[...] FETCH data item, 4847 servers MUST ensure that textual line-oriented sections are 4848 always transmitted using the IMAP4 CRLF line termination 4849 syntax, regardless of the underlying storage representation of 4850 the data on the server. 4852 If the server does not know how to decode the section's 4853 Content-Transfer-Encoding, it MUST fail the request and issue a 4854 "NO" response that contains the "UNKNOWN-CTE" response code. 4856 BINARY.SIZE[] 4858 The size of the section after removing any Content-Transfer- 4859 Encoding-related encoding. The value returned MUST match the 4860 size of the or that will be returned by 4861 the corresponding FETCH BINARY request. 4863 If the server does not know how to decode the section's 4864 Content-Transfer-Encoding, it MUST fail the request and issue a 4865 "NO" response that contains the "UNKNOWN-CTE" response code. 4867 BODY A form of BODYSTRUCTURE without extension data. 4869 BODY[
]<> 4871 A string expressing the body contents of the specified section. 4872 The string SHOULD be interpreted by the client according to the 4873 content transfer encoding, body type, and subtype. 4875 If the origin octet is specified, this string is a substring of 4876 the entire body contents, starting at that origin octet. This 4877 means that BODY[]<0> MAY be truncated, but BODY[] is NEVER 4878 truncated. 4880 Note: The origin octet facility MUST NOT be used by a server 4881 in a FETCH response unless the client specifically requested 4882 it by means of a FETCH of a BODY[
]<> data 4883 item. 4885 8-bit textual data is permitted if a [CHARSET] identifier is 4886 part of the body parameter parenthesized list for this section. 4887 Note that headers (part specifiers HEADER or MIME, or the 4888 header portion of a MESSAGE/RFC822 or MESSAGE/GLOBAL part), MAY 4889 be in UTF-8. Note also that the [RFC-5322] delimiting blank 4890 line between the header and the body is not affected by header 4891 line subsetting; the blank line is always included as part of 4892 header data, except in the case of a message which has no body 4893 and no blank line. 4895 Non-textual data such as binary data MUST be transfer encoded 4896 into a textual form, such as BASE64, prior to being sent to the 4897 client. To derive the original binary data, the client MUST 4898 decode the transfer encoded string. 4900 BODYSTRUCTURE 4902 A parenthesized list that describes the [MIME-IMB] body 4903 structure of a message. This is computed by the server by 4904 parsing the [MIME-IMB] header fields, defaulting various fields 4905 as necessary. 4907 For example, a simple text message of 48 lines and 2279 octets 4908 can have a body structure of: ("TEXT" "PLAIN" ("CHARSET" "US- 4909 ASCII") NIL NIL "7BIT" 2279 48) 4911 Multiple parts are indicated by parenthesis nesting. Instead 4912 of a body type as the first element of the parenthesized list, 4913 there is a sequence of one or more nested body structures. The 4914 second element of the parenthesized list is the multipart 4915 subtype (mixed, digest, parallel, alternative, etc.). 4917 For example, a two part message consisting of a text and a 4918 BASE64-encoded text attachment can have a body structure of: 4919 (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 4920 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff") 4921 "<960723163407.20117h@cac.washington.edu>" "Compiler diff" 4922 "BASE64" 4554 73) "MIXED") 4924 Extension data follows the multipart subtype. Extension data 4925 is never returned with the BODY fetch, but can be returned with 4926 a BODYSTRUCTURE fetch. Extension data, if present, MUST be in 4927 the defined order. The extension data of a multipart body part 4928 are in the following order: 4930 body parameter parenthesized list A parenthesized list of 4931 attribute/value pairs [e.g., ("foo" "bar" "baz" "rag") where 4932 "bar" is the value of "foo", and "rag" is the value of 4933 "baz"] as defined in [MIME-IMB]. Servers SHOULD decode 4934 parameter value continuations as described in [RFC2231]. 4936 body disposition A parenthesized list, consisting of a 4937 disposition type string, followed by a parenthesized list of 4938 disposition attribute/value pairs as defined in 4939 [DISPOSITION]. Servers SHOULD decode parameter value 4940 continuations as described in [RFC2231]. 4942 body language A string or parenthesized list giving the body 4943 language value as defined in [LANGUAGE-TAGS]. 4945 body location A string giving the body content URI as defined 4946 in [LOCATION]. 4948 Any following extension data are not yet defined in this 4949 version of the protocol. Such extension data can consist of 4950 zero or more NILs, strings, numbers, or potentially nested 4951 parenthesized lists of such data. Client implementations that 4952 do a BODYSTRUCTURE fetch MUST be prepared to accept such 4953 extension data. Server implementations MUST NOT send such 4954 extension data until it has been defined by a revision of this 4955 protocol. 4957 The basic fields of a non-multipart body part are in the 4958 following order: 4960 body type A string giving the content media type name as 4961 defined in [MIME-IMB]. 4963 body subtype A string giving the content subtype name as 4964 defined in [MIME-IMB]. 4966 body parameter parenthesized list A parenthesized list of 4967 attribute/value pairs [e.g., ("foo" "bar" "baz" "rag") where 4968 "bar" is the value of "foo" and "rag" is the value of "baz"] 4969 as defined in [MIME-IMB]. 4971 body id A string giving the Content-ID header field value as 4972 defined in Section 7 of [MIME-IMB]. 4974 body description A string giving the Content-Description 4975 header field value as defined in Section 8 of [MIME-IMB]. 4977 body encoding A string giving the content transfer encoding as 4978 defined in Section 6 of [MIME-IMB]. 4980 body size A number giving the size of the body in octets. 4981 Note that this size is the size in its transfer encoding and 4982 not the resulting size after any decoding. 4984 A body type of type MESSAGE and subtype RFC822 contains, 4985 immediately after the basic fields, the envelope structure, 4986 body structure, and size in text lines of the encapsulated 4987 message. 4989 A body type of type TEXT contains, immediately after the basic 4990 fields, the size of the body in text lines. Note that this 4991 size is the size in its content transfer encoding and not the 4992 resulting size after any decoding. 4994 Extension data follows the basic fields and the type-specific 4995 fields listed above. Extension data is never returned with the 4996 BODY fetch, but can be returned with a BODYSTRUCTURE fetch. 4997 Extension data, if present, MUST be in the defined order. 4999 The extension data of a non-multipart body part are in the 5000 following order: 5002 body MD5 A string giving the body MD5 value as defined in 5003 [MD5]. 5005 body disposition A parenthesized list with the same content 5006 and function as the body disposition for a multipart body 5007 part. 5009 body language A string or parenthesized list giving the body 5010 language value as defined in [LANGUAGE-TAGS]. 5012 body location A string giving the body content URI as defined 5013 in [LOCATION]. 5015 Any following extension data are not yet defined in this 5016 version of the protocol, and would be as described above under 5017 multipart extension data. 5019 ENVELOPE 5021 A parenthesized list that describes the envelope structure of a 5022 message. This is computed by the server by parsing the 5023 [RFC-5322] header into the component parts, defaulting various 5024 fields as necessary. 5026 The fields of the envelope structure are in the following 5027 order: date, subject, from, sender, reply-to, to, cc, bcc, in- 5028 reply-to, and message-id. The date, subject, in-reply-to, and 5029 message-id fields are strings. The from, sender, reply-to, to, 5030 cc, and bcc fields are parenthesized lists of address 5031 structures. 5033 An address structure is a parenthesized list that describes an 5034 electronic mail address. The fields of an address structure 5035 are in the following order: personal name, [SMTP] at-domain- 5036 list (source route), mailbox name, and host name. 5038 [RFC-5322] group syntax is indicated by a special form of 5039 address structure in which the host name field is NIL. If the 5040 mailbox name field is also NIL, this is an end of group marker 5041 (semi-colon in RFC 822 syntax). If the mailbox name field is 5042 non-NIL, this is a start of group marker, and the mailbox name 5043 field holds the group name phrase. 5045 If the Date, Subject, In-Reply-To, and Message-ID header lines 5046 are absent in the [RFC-5322] header, the corresponding member 5047 of the envelope is NIL; if these header lines are present but 5048 empty the corresponding member of the envelope is the empty 5049 string. 5051 Note: some servers may return a NIL envelope member in the 5052 "present but empty" case. Clients SHOULD treat NIL and 5053 empty string as identical. 5055 Note: [RFC-5322] requires that all messages have a valid 5056 Date header. Therefore, the date member in the envelope can 5057 not be NIL or the empty string. 5059 Note: [RFC-5322] requires that the In-Reply-To and Message- 5060 ID headers, if present, have non-empty content. Therefore, 5061 the in-reply-to and message-id members in the envelope can 5062 not be the empty string. 5064 If the From, To, Cc, and Bcc header lines are absent in the 5065 [RFC-5322] header, or are present but empty, the corresponding 5066 member of the envelope is NIL. 5068 If the Sender or Reply-To lines are absent in the [RFC-5322] 5069 header, or are present but empty, the server sets the 5070 corresponding member of the envelope to be the same value as 5071 the from member (the client is not expected to know to do 5072 this). 5074 Note: [RFC-5322] requires that all messages have a valid 5075 From header. Therefore, the from, sender, and reply-to 5076 members in the envelope can not be NIL. 5078 FLAGS A parenthesized list of flags that are set for this message. 5080 INTERNALDATE A string representing the internal date of the message. 5082 RFC822 Equivalent to BODY[]. 5084 RFC822.HEADER Equivalent to BODY[HEADER]. Note that this did not 5085 result in \Seen being set, because RFC822.HEADER response data 5086 occurs as a result of a FETCH of RFC822.HEADER. BODY[HEADER] 5087 response data occurs as a result of a FETCH of BODY[HEADER] (which 5088 sets \Seen) or BODY.PEEK[HEADER] (which does not set \Seen). 5090 RFC822.SIZE A number expressing the [RFC-5322] size of the message. 5092 RFC822.TEXT Equivalent to BODY[TEXT]. 5094 UID A number expressing the unique identifier of the message. 5096 Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827) 5098 7.5. Server Responses - Command Continuation Request 5100 The command continuation request response is indicated by a "+" token 5101 instead of a tag. This form of response indicates that the server is 5102 ready to accept the continuation of a command from the client. The 5103 remainder of this response is a line of text. 5105 This response is used in the AUTHENTICATE command to transmit server 5106 data to the client, and request additional client data. This 5107 response is also used if an argument to any command is a 5108 synchronizing literal. 5110 The client is not permitted to send the octets of the synchronizing 5111 literal unless the server indicates that it is expected. This 5112 permits the server to process commands and reject errors on a line- 5113 by-line basis. The remainder of the command, including the CRLF that 5114 terminates a command, follows the octets of the literal. If there 5115 are any additional command arguments, the literal octets are followed 5116 by a space and those arguments. 5118 Example: C: A001 LOGIN {11} 5119 S: + Ready for additional command text 5120 C: FRED FOOBAR {7} 5121 S: + Ready for additional command text 5122 C: fat man 5123 S: A001 OK LOGIN completed 5124 C: A044 BLURDYBLOOP {102856} 5125 S: A044 BAD No such command as "BLURDYBLOOP" 5127 8. Sample IMAP4rev2 connection 5129 The following is a transcript of an IMAP4rev2 connection. A long 5130 line in this sample is broken for editorial clarity. 5132 S: * OK IMAP4rev2 Service Ready 5133 C: a001 login mrc secret 5134 S: a001 OK LOGIN completed 5135 C: a002 select inbox 5136 S: * 18 EXISTS 5137 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 5138 S: * OK [UIDVALIDITY 3857529045] UIDs valid 5139 S: a002 OK [READ-WRITE] SELECT completed 5140 C: a003 fetch 12 full 5141 S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700" 5142 RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)" 5143 "IMAP4rev2 WG mtg summary and minutes" 5144 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5145 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5146 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5147 ((NIL NIL "imap" "cac.washington.edu")) 5148 ((NIL NIL "minutes" "CNRI.Reston.VA.US") 5149 ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL 5150 "") 5151 BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 5152 92)) 5153 S: a003 OK FETCH completed 5154 C: a004 fetch 12 body[header] 5155 S: * 12 FETCH (BODY[HEADER] {342} 5156 S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT) 5157 S: From: Terry Gray 5158 S: Subject: IMAP4rev2 WG mtg summary and minutes 5159 S: To: imap@cac.washington.edu 5160 S: cc: minutes@CNRI.Reston.VA.US, John Klensin 5161 S: Message-Id: 5162 S: MIME-Version: 1.0 5163 S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 5164 S: 5165 S: ) 5166 S: a004 OK FETCH completed 5167 C: a005 store 12 +flags \deleted 5168 S: * 12 FETCH (FLAGS (\Seen \Deleted)) 5169 S: a005 OK +FLAGS completed 5170 C: a006 logout 5171 S: * BYE IMAP4rev2 server terminating connection 5172 S: a006 OK LOGOUT completed 5174 9. Formal Syntax 5176 The following syntax specification uses the Augmented Backus-Naur 5177 Form (ABNF) notation as specified in [ABNF]. 5179 In the case of alternative or optional rules in which a later rule 5180 overlaps an earlier rule, the rule which is listed earlier MUST take 5181 priority. For example, "\Seen" when parsed as a flag is the \Seen 5182 flag name and not a flag-extension, even though "\Seen" can be parsed 5183 as a flag-extension. Some, but not all, instances of this rule are 5184 noted below. 5186 Note: [ABNF] rules MUST be followed strictly; in particular: 5188 (1) Except as noted otherwise, all alphabetic characters are case- 5189 insensitive. The use of upper or lower case characters to define 5190 token strings is for editorial clarity only. Implementations MUST 5191 accept these strings in a case-insensitive fashion. 5193 (2) In all cases, SP refers to exactly one space. It is NOT 5194 permitted to substitute TAB, insert additional spaces, or 5195 otherwise treat SP as being equivalent to LWSP. 5197 (3) The ASCII NUL character, %x00, MUST NOT be used at any time. 5199 address = "(" addr-name SP addr-adl SP addr-mailbox SP 5200 addr-host ")" 5202 addr-adl = nstring 5203 ; Holds route from [RFC-5322] route-addr if 5204 ; non-NIL 5206 addr-host = nstring 5207 ; NIL indicates [RFC-5322] group syntax. 5208 ; Otherwise, holds [RFC-5322] domain name 5210 addr-mailbox = nstring 5211 ; NIL indicates end of [RFC-5322] group; if 5212 ; non-NIL and addr-host is NIL, holds 5213 ; [RFC-5322] group name. 5214 ; Otherwise, holds [RFC-5322] local-part 5215 ; after removing [RFC-5322] quoting 5217 addr-name = nstring 5218 ; If non-NIL, holds phrase from [RFC-5322] 5219 ; mailbox after removing [RFC-5322] quoting 5221 append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP 5222 literal 5224 append-uid = uniqueid 5226 astring = 1*ASTRING-CHAR / string 5227 ASTRING-CHAR = ATOM-CHAR / resp-specials 5229 atom = 1*ATOM-CHAR 5231 ATOM-CHAR = 5233 atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards / 5234 quoted-specials / resp-specials 5236 authenticate = "AUTHENTICATE" SP auth-type [SP initial-resp] 5237 *(CRLF base64) 5239 auth-type = atom 5240 ; Defined by [SASL] 5242 base64 = *(4base64-char) [base64-terminal] 5244 base64-char = ALPHA / DIGIT / "+" / "/" 5245 ; Case-sensitive 5247 base64-terminal = (2base64-char "==") / (3base64-char "=") 5249 body = "(" (body-type-1part / body-type-mpart) ")" 5251 body-extension = nstring / number / 5252 "(" body-extension *(SP body-extension) ")" 5253 ; Future expansion. Client implementations 5254 ; MUST accept body-extension fields. Server 5255 ; implementations MUST NOT generate 5256 ; body-extension fields except as defined by 5257 ; future standard or standards-track 5258 ; revisions of this specification. 5260 body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang 5261 [SP body-fld-loc *(SP body-extension)]]] 5262 ; MUST NOT be returned on non-extensible 5263 ; "BODY" fetch 5265 body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang 5266 [SP body-fld-loc *(SP body-extension)]]] 5267 ; MUST NOT be returned on non-extensible 5268 ; "BODY" fetch 5270 body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP 5271 body-fld-enc SP body-fld-octets 5273 body-fld-desc = nstring 5274 body-fld-dsp = "(" string SP body-fld-param ")" / nil 5276 body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/ 5277 "QUOTED-PRINTABLE") DQUOTE) / string 5279 body-fld-id = nstring 5281 body-fld-lang = nstring / "(" string *(SP string) ")" 5283 body-fld-loc = nstring 5285 body-fld-lines = number 5287 body-fld-md5 = nstring 5289 body-fld-octets = number 5291 body-fld-param = "(" string SP string *(SP string SP string) ")" / nil 5293 body-type-1part = (body-type-basic / body-type-msg / body-type-text) 5294 [SP body-ext-1part] 5296 body-type-basic = media-basic SP body-fields 5297 ; MESSAGE subtype MUST NOT be "RFC822" or "GLOBAL" 5299 body-type-mpart = 1*body SP media-subtype 5300 [SP body-ext-mpart] 5301 ; MULTIPART body part 5303 body-type-msg = media-message SP body-fields SP envelope 5304 SP body SP body-fld-lines 5306 body-type-text = media-text SP body-fields SP body-fld-lines 5308 capability = ("AUTH=" auth-type) / atom 5309 ; New capabilities MUST begin with "X" or be 5310 ; registered with IANA as standard or 5311 ; standards-track 5313 capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev2" 5314 *(SP capability) 5315 ; Servers MUST implement the STARTTLS, AUTH=PLAIN, 5316 ; and LOGINDISABLED capabilities 5317 ; Servers which offer RFC 1730 compatibility MUST 5318 ; list "IMAP4" as the first capability. 5320 CHAR8 = %x01-ff 5321 ; any OCTET except NUL, %x00 5323 charset = atom / quoted 5325 childinfo-extended-item = "CHILDINFO" SP "(" 5326 list-select-base-opt-quoted 5327 *(SP list-select-base-opt-quoted) ")" 5328 ; Extended data item (mbox-list-extended-item) 5329 ; returned when the RECURSIVEMATCH 5330 ; selection option is specified. 5331 ; Note 1: the CHILDINFO tag can be returned 5332 ; with and without surrounding quotes, as per 5333 ; mbox-list-extended-item-tag production. 5334 ; Note 2: The selection options are always returned 5335 ; quoted, unlike their specification in 5336 ; the extended LIST command. 5338 child-mbox-flag = "\HasChildren" / "\HasNoChildren" 5339 ; attributes for CHILDREN return option, at most one 5340 ; possible per LIST response 5342 command = tag SP (command-any / command-auth / command-nonauth / 5343 command-select) CRLF 5344 ; Modal based on state 5346 command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / enable / x-command 5347 ; Valid in all states 5349 command-auth = append / create / delete / examine / list / 5350 Namespace-Command / 5351 rename / select / status / subscribe / unsubscribe / 5352 idle 5353 ; Valid only in Authenticated or Selected state 5355 command-nonauth = login / authenticate / "STARTTLS" 5356 ; Valid only when in Not Authenticated state 5358 command-select = "CLOSE" / "UNSELECT" / "EXPUNGE" / copy / 5359 move / fetch / store / search / uid 5360 ; Valid only when in Selected state 5362 continue-req = "+" SP (resp-text / base64) CRLF 5364 copy = "COPY" SP sequence-set SP mailbox 5366 create = "CREATE" SP mailbox 5367 ; Use of INBOX gives a NO error 5369 date = date-text / DQUOTE date-text DQUOTE 5370 date-day = 1*2DIGIT 5371 ; Day of month 5373 date-day-fixed = (SP DIGIT) / 2DIGIT 5374 ; Fixed-format version of date-day 5376 date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" / 5377 "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec" 5379 date-text = date-day "-" date-month "-" date-year 5381 date-year = 4DIGIT 5383 date-time = DQUOTE date-day-fixed "-" date-month "-" date-year 5384 SP time SP zone DQUOTE 5386 delete = "DELETE" SP mailbox 5387 ; Use of INBOX gives a NO error 5389 digit-nz = %x31-39 5390 ; 1-9 5392 eitem-standard-tag = atom 5393 ; a tag for extended list data defined in a Standard 5394 ; Track or Experimental RFC. 5396 eitem-vendor-tag = vendor-token "-" atom 5397 ; a vendor-specific tag for extended list data 5399 enable = "ENABLE" 1*(SP capability) 5401 enable-data = "ENABLED" *(SP capability) 5403 envelope = "(" env-date SP env-subject SP env-from SP 5404 env-sender SP env-reply-to SP env-to SP env-cc SP 5405 env-bcc SP env-in-reply-to SP env-message-id ")" 5407 env-bcc = "(" 1*address ")" / nil 5409 env-cc = "(" 1*address ")" / nil 5411 env-date = nstring 5413 env-from = "(" 1*address ")" / nil 5415 env-in-reply-to = nstring 5417 env-message-id = nstring 5418 env-reply-to = "(" 1*address ")" / nil 5420 env-sender = "(" 1*address ")" / nil 5422 env-subject = nstring 5424 env-to = "(" 1*address ")" / nil 5426 esearch-response = "ESEARCH" [search-correlator] [SP "UID"] 5427 *(SP search-return-data) 5428 ; ESEARCH response replaces SEARCH response 5429 ; from IMAP4rev1. 5431 examine = "EXAMINE" SP mailbox 5433 fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" / 5434 fetch-att / "(" fetch-att *(SP fetch-att) ")") 5436 fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" / 5437 "RFC822.SIZE" / 5438 "BODY" ["STRUCTURE"] / "UID" / 5439 "BODY" section [partial] / 5440 "BODY.PEEK" section [partial] / 5441 "BINARY" [".PEEK"] section-binary [partial] / 5442 "BINARY.SIZE" section-binary / 5443 fetch-att-deprecated 5445 fetch-att-deprecated = "RFC822" [".HEADER" / .TEXT"] 5447 flag = "\Answered" / "\Flagged" / "\Deleted" / 5448 "\Seen" / "\Draft" / flag-keyword / flag-extension 5449 ; Does not include "\Recent" 5451 flag-extension = "\" atom 5452 ; Future expansion. Client implementations 5453 ; MUST accept flag-extension flags. Server 5454 ; implementations MUST NOT generate 5455 ; flag-extension flags except as defined by 5456 ; future standard or standards-track 5457 ; revisions of this specification. 5458 ; "\Recent" was defined in RFC 3501 5459 ; and is now deprecated. 5461 flag-fetch = flag 5463 flag-keyword = "$MDNSent" / "$Forwarded" / atom 5465 flag-list = "(" [flag *(SP flag)] ")" 5466 flag-perm = flag / "\*" 5468 greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF 5470 header-fld-name = astring 5472 header-list = "(" header-fld-name *(SP header-fld-name) ")" 5474 idle = "IDLE" CRLF "DONE" 5476 initial-resp = (base64 / "=") 5477 ; "initial response" defined in 5478 ; Section 5.1 of [RFC4422] 5480 list = "LIST" [SP list-select-opts] SP mailbox SP mbox-or-pat 5481 [SP list-return-opts] 5483 list-mailbox = 1*list-char / string 5485 list-char = ATOM-CHAR / list-wildcards / resp-specials 5487 list-return-opts = "RETURN" SP 5488 "(" [return-option *(SP return-option)] ")" 5489 ; list return options, e.g., CHILDREN 5491 list-select-base-opt = "SUBSCRIBED" / option-extension 5492 ; options that can be used by themselves 5494 list-select-base-opt-quoted = DQUOTE list-select-base-opt DQUOTE 5496 list-select-independent-opt = "REMOTE" / option-extension 5497 ; options that do not syntactically interact with 5498 ; other options 5500 list-select-mod-opt = "RECURSIVEMATCH" / option-extension 5501 ; options that require a list-select-base-opt 5502 ; to also be present 5504 list-select-opt = list-select-base-opt / list-select-independent-opt 5505 / list-select-mod-opt 5506 ; An option registration template is described in 5507 ; Section 9.3 of this document. 5509 list-select-opts = "(" [ 5510 (*(list-select-opt SP) list-select-base-opt 5511 *(SP list-select-opt)) 5512 / (list-select-independent-opt 5513 *(SP list-select-independent-opt)) 5514 ] ")" 5515 ; Any number of options may be in any order. 5516 ; If a list-select-mod-opt appears, then a 5517 ; list-select-base-opt must also appear. 5518 ; This allows these: 5519 ; () 5520 ; (REMOTE) 5521 ; (SUBSCRIBED) 5522 ; (SUBSCRIBED REMOTE) 5523 ; (SUBSCRIBED RECURSIVEMATCH) 5524 ; (SUBSCRIBED REMOTE RECURSIVEMATCH) 5525 ; But does NOT allow these: 5526 ; (RECURSIVEMATCH) 5527 ; (REMOTE RECURSIVEMATCH) 5529 list-wildcards = "%" / "*" 5531 literal = "{" number ["+"] "}" CRLF *CHAR8 5532 ; represents the number of CHAR8s. 5533 ; A non-synchronizing literal is distinguished from 5534 ; a synchronizing literal by presence of the "+" 5535 ; before the closing "}". 5536 ; Non synchronizing literals are not allowed when 5537 ; sent from server to the client. 5539 literal8 = "~{" number "}" CRLF *OCTET 5540 ; represents the number of OCTETs 5541 ; in the response string. 5543 login = "LOGIN" SP userid SP password 5545 mailbox = "INBOX" / astring 5546 ; INBOX is case-insensitive. All case variants of 5547 ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX 5548 ; not as an astring. An astring which consists of 5549 ; the case-insensitive sequence "I" "N" "B" "O" "X" 5550 ; is considered to be INBOX and not an astring. 5551 ; Refer to section 5.1 for further 5552 ; semantic details of mailbox names. 5554 mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list / 5555 esearch-response / 5556 "STATUS" SP mailbox SP "(" [status-att-list] ")" / 5557 number SP "EXISTS" / Namespace-Response 5559 mailbox-list = "(" [mbx-list-flags] ")" SP 5560 (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox 5562 [SP mbox-list-extended] 5563 ; This is the list information pointed to by the ABNF 5564 ; item "mailbox-data", which is defined in [IMAP4] 5566 mbox-list-extended = "(" [mbox-list-extended-item 5567 *(SP mbox-list-extended-item)] ")" 5569 mbox-list-extended-item = mbox-list-extended-item-tag SP 5570 tagged-ext-val 5572 mbox-list-extended-item-tag = astring 5573 ; The content MUST conform to either "eitem-vendor-tag" 5574 ; or "eitem-standard-tag" ABNF productions. 5576 mbox-or-pat = list-mailbox / patterns 5578 mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag 5579 *(SP mbx-list-oflag) / 5580 mbx-list-oflag *(SP mbx-list-oflag) 5582 mbx-list-oflag = "\Noinferiors" / child-mbox-flag / 5583 "\Subscribed" / "\Remote" / flag-extension 5584 ; Other flags; multiple possible per LIST response 5586 mbx-list-sflag = "\NonExistent" / "\Noselect" / "\Marked" / "\Unmarked" 5587 ; Selectability flags; only one per LIST response 5589 media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" / 5590 "MESSAGE" / "VIDEO" / "FONT") DQUOTE) / string) SP 5591 media-subtype 5592 ; Defined in [MIME-IMT]. 5593 ; FONT defined in RFC YYYY. 5595 media-message = DQUOTE "MESSAGE" DQUOTE SP 5596 DQUOTE ("RFC822" / "GLOBAL") DQUOTE 5597 ; Defined in [MIME-IMT] 5599 media-subtype = string 5600 ; Defined in [MIME-IMT] 5602 media-text = DQUOTE "TEXT" DQUOTE SP media-subtype 5603 ; Defined in [MIME-IMT] 5605 message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att)) 5607 move = "MOVE" SP sequence-set SP mailbox 5609 msg-att = "(" (msg-att-dynamic / msg-att-static) 5610 *(SP (msg-att-dynamic / msg-att-static)) ")" 5612 msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")" 5613 ; MAY change for a message 5615 msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time / 5616 "RFC822" [".HEADER" / ".TEXT"] SP nstring / 5617 "RFC822.SIZE" SP number / 5618 "BODY" ["STRUCTURE"] SP body / 5619 "BODY" section ["<" number ">"] SP nstring / 5620 "BINARY" section-binary SP (nstring / literal8) / 5621 "BINARY.SIZE" section-binary SP number / 5622 "UID" SP uniqueid 5623 ; MUST NOT change for a message 5625 Namespace = nil / "(" 1*Namespace-Descr ")" 5627 Namespace-Command = "NAMESPACE" 5629 Namespace-Descr = "(" string SP 5630 (DQUOTE QUOTED-CHAR DQUOTE / nil) 5631 [Namespace-Response-Extensions] ")" 5633 Namespace-Response-Extensions = *(Namespace-Response-Extension) 5635 Namespace-Response-Extension = SP string SP 5636 "(" string *(SP string) ")" 5638 Namespace-Response = "NAMESPACE" SP Namespace 5639 SP Namespace SP Namespace 5640 ; The first Namespace is the Personal Namespace(s) 5641 ; The second Namespace is the Other Users' Namespace(s) 5642 ; The third Namespace is the Shared Namespace(s) 5644 nil = "NIL" 5646 nstring = string / nil 5648 number = 1*DIGIT 5649 ; Unsigned 32-bit integer 5650 ; (0 <= n < 4,294,967,296) 5652 number64 = 1*DIGIT 5653 ; Unsigned 63-bit integer 5654 ; (0 <= n <= 9,223,372,036,854,775,807) 5656 nz-number = digit-nz *DIGIT 5657 ; Non-zero unsigned 32-bit integer 5658 ; (0 < n < 4,294,967,296) 5660 option-extension = (option-standard-tag / option-vendor-tag) 5661 [SP option-value] 5663 option-standard-tag = atom 5664 ; an option defined in a Standards Track or 5665 ; Experimental RFC 5667 option-val-comp = astring / 5668 option-val-comp *(SP option-val-comp) / 5669 "(" option-val-comp ")" 5671 option-value = "(" option-val-comp ")" 5673 option-vendor-tag = vendor-token "-" atom 5674 ; a vendor-specific option, non-standard 5676 partial-range = number ["." nz-number] 5677 ; Copied from RFC 5092 (IMAP URL) 5679 partial = "<" number "." nz-number ">" 5680 ; Partial FETCH request. 0-based offset of 5681 ; the first octet, followed by the number of octets 5682 ; in the fragment. 5684 password = astring 5686 patterns = "(" list-mailbox *(SP list-mailbox) ")" 5688 quoted = DQUOTE *QUOTED-CHAR DQUOTE 5690 QUOTED-CHAR = / 5691 "\" quoted-specials / UTF8-2 / UTF8-3 / UTF8-4 5693 quoted-specials = DQUOTE / "\" 5695 rename = "RENAME" SP mailbox SP mailbox 5696 ; Use of INBOX as a destination gives a NO error 5698 response = *(continue-req / response-data) response-done 5700 response-data = "*" SP (resp-cond-state / resp-cond-bye / 5701 mailbox-data / message-data / capability-data / 5702 enable-data) CRLF 5704 response-done = response-tagged / response-fatal 5705 response-fatal = "*" SP resp-cond-bye CRLF 5706 ; Server closes connection immediately 5708 response-tagged = tag SP resp-cond-state CRLF 5710 resp-code-apnd = "APPENDUID" SP nz-number SP append-uid 5712 resp-code-copy = "COPYUID" SP nz-number SP uid-set SP uid-set 5714 resp-cond-auth = ("OK" / "PREAUTH") SP resp-text 5715 ; Authentication condition 5717 resp-cond-bye = "BYE" SP resp-text 5719 resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text 5720 ; Status condition 5722 resp-specials = "]" 5724 ;; ////Can we make "text" optional? Will this have any bad side effects? 5725 resp-text = ["[" resp-text-code "]" SP] text 5727 resp-text-code = "ALERT" / 5728 "BADCHARSET" [SP "(" charset *(SP charset) ")" ] / 5729 capability-data / "PARSE" / 5730 "PERMANENTFLAGS" SP "(" 5731 [flag-perm *(SP flag-perm)] ")" / 5732 "READ-ONLY" / "READ-WRITE" / "TRYCREATE" / 5733 "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number / 5734 resp-code-apnd / resp-code-copy / "UIDNOTSTICKY" / 5735 "UNAVAILABLE" / "AUTHENTICATIONFAILED" / 5736 "AUTHORIZATIONFAILED" / "EXPIRED" / 5737 "PRIVACYREQUIRED" / "CONTACTADMIN" / "NOPERM" / 5738 "INUSE" / "EXPUNGEISSUED" / "CORRUPTION" / 5739 "SERVERBUG" / "CLIENTBUG" / "CANNOT" / 5740 "LIMIT" / "OVERQUOTA" / "ALREADYEXISTS" / 5741 "NONEXISTENT" / 5742 "CLOSED" / 5743 "UNKNOWN-CTE" / 5744 atom [SP 1*] 5746 return-option = "SUBSCRIBED" / "CHILDREN" / option-extension 5748 search = "SEARCH" [search-return-opts] 5749 SP search-program 5751 search-correlator = SP "(" "TAG" SP tag-string ")" 5752 search-key = "ALL" / "ANSWERED" / "BCC" SP astring / 5753 "BEFORE" SP date / "BODY" SP astring / 5754 "CC" SP astring / "DELETED" / "FLAGGED" / 5755 "FROM" SP astring / "KEYWORD" SP flag-keyword / 5756 "NEW" / "OLD" / "ON" SP date / "SEEN" / 5757 "SINCE" SP date / "SUBJECT" SP astring / 5758 "TEXT" SP astring / "TO" SP astring / 5759 "UNANSWERED" / "UNDELETED" / "UNFLAGGED" / 5760 "UNKEYWORD" SP flag-keyword / "UNSEEN" / 5761 ; Above this line were in [IMAP2] 5762 "DRAFT" / "HEADER" SP header-fld-name SP astring / 5763 "LARGER" SP number / "NOT" SP search-key / 5764 "OR" SP search-key SP search-key / 5765 "SENTBEFORE" SP date / "SENTON" SP date / 5766 "SENTSINCE" SP date / "SMALLER" SP number / 5767 "UID" SP sequence-set / "UNDRAFT" / sequence-set / 5768 "(" search-key *(SP search-key) ")" 5770 search-modifier-name = tagged-ext-label 5772 search-mod-params = tagged-ext-val 5773 ; This non-terminal shows recommended syntax 5774 ; for future extensions. 5776 search-program = ["CHARSET" SP charset SP] 5777 search-key *(SP search-key) 5778 ; CHARSET argument to SEARCH MUST be 5779 ; registered with IANA. 5781 search-ret-data-ext = search-modifier-name SP search-return-value 5782 ; Note that not every SEARCH return option 5783 ; is required to have the corresponding 5784 ; ESEARCH return data. 5786 search-return-data = "MIN" SP nz-number / 5787 "MAX" SP nz-number / 5788 "ALL" SP sequence-set / 5789 "COUNT" SP number / 5790 search-ret-data-ext 5791 ; All return data items conform to 5792 ; search-ret-data-ext syntax 5794 search-return-opts = SP "RETURN" SP "(" [search-return-opt 5795 *(SP search-return-opt)] ")" 5797 search-return-opt = "MIN" / "MAX" / "ALL" / "COUNT" / 5798 search-ret-opt-ext 5799 ; conforms to generic search-ret-opt-ext 5800 ; syntax 5802 search-ret-opt-ext = search-modifier-name [SP search-mod-params] 5804 search-return-value = tagged-ext-val 5805 ; Data for the returned search option. 5806 ; A single "nz-number"/"number"/"number64" value 5807 ; can be returned as an atom (i.e., without 5808 ; quoting). A sequence-set can be returned 5809 ; as an atom as well. 5811 section = "[" [section-spec] "]" 5813 section-binary = "[" [section-part] "]" 5815 section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list / 5816 "TEXT" 5817 ; top-level or MESSAGE/RFC822 or MESSAGE/GLOBAL part 5819 section-part = nz-number *("." nz-number) 5820 ; body part reference. 5821 ; Allows for accessing nested body parts. 5823 section-spec = section-msgtext / (section-part ["." section-text]) 5825 section-text = section-msgtext / "MIME" 5826 ; text other than actual body part (headers, etc.) 5828 select = "SELECT" SP mailbox 5830 seq-number = nz-number / "*" 5831 ; message sequence number (COPY, FETCH, STORE 5832 ; commands) or unique identifier (UID COPY, 5833 ; UID FETCH, UID STORE commands). 5834 ; * represents the largest number in use. In 5835 ; the case of message sequence numbers, it is 5836 ; the number of messages in a non-empty mailbox. 5837 ; In the case of unique identifiers, it is the 5838 ; unique identifier of the last message in the 5839 ; mailbox or, if the mailbox is empty, the 5840 ; mailbox's current UIDNEXT value. 5841 ; The server should respond with a tagged BAD 5842 ; response to a command that uses a message 5843 ; sequence number greater than the number of 5844 ; messages in the selected mailbox. This 5845 ; includes "*" if the selected mailbox is empty. 5847 seq-range = seq-number ":" seq-number 5848 ; two seq-number values and all values between 5849 ; these two regardless of order. 5850 ; Example: 2:4 and 4:2 are equivalent and indicate 5851 ; values 2, 3, and 4. 5852 ; Example: a unique identifier sequence range of 5853 ; 3291:* includes the UID of the last message in 5854 ; the mailbox, even if that value is less than 3291. 5856 sequence-set = (seq-number / seq-range) ["," sequence-set] 5857 ; set of seq-number values, regardless of order. 5858 ; Servers MAY coalesce overlaps and/or execute the 5859 ; sequence in any order. 5860 ; Example: a message sequence number set of 5861 ; 2,4:7,9,12:* for a mailbox with 15 messages is 5862 ; equivalent to 2,4,5,6,7,9,12,13,14,15 5863 ; Example: a message sequence number set of *:4,5:7 5864 ; for a mailbox with 10 messages is equivalent to 5865 ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and 5866 ; overlap coalesced to be 4,5,6,7,8,9,10. 5868 status = "STATUS" SP mailbox SP 5869 "(" status-att *(SP status-att) ")" 5871 status-att = "MESSAGES" / "UIDNEXT" / "UIDVALIDITY" / 5872 "UNSEEN" / "SIZE" 5874 status-att-val = ("MESSAGES" SP number) / 5875 ("UIDNEXT" SP nz-number) / 5876 ("UIDVALIDITY" SP nz-number) / 5877 ("UNSEEN" SP number) / 5878 ("SIZE" SP number64) 5879 ; Extensions to the STATUS responses 5880 ; should extend this production. 5881 ; Extensions should use the generic 5882 ; syntax defined by tagged-ext. 5884 status-att-list = status-att-val *(SP status-att-val) 5886 store = "STORE" SP sequence-set SP store-att-flags 5888 store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP 5889 (flag-list / (flag *(SP flag))) 5891 string = quoted / literal 5893 subscribe = "SUBSCRIBE" SP mailbox 5895 tag = 1* 5896 tagged-ext-label = tagged-label-fchar *tagged-label-char 5897 ;; Is a valid RFC 3501 "atom". 5899 tagged-label-fchar = ALPHA / "-" / "_" / "." 5901 tagged-label-char = tagged-label-fchar / DIGIT / ":" 5903 tagged-ext-comp = astring / 5904 tagged-ext-comp *(SP tagged-ext-comp) / 5905 "(" tagged-ext-comp ")" 5906 ;; Extensions that follow this general 5907 ;; syntax should use nstring instead of 5908 ;; astring when appropriate in the context 5909 ;; of the extension. 5910 ;; Note that a message set or a "number" 5911 ;; can always be represented as an "atom". 5912 ;; An URL should be represented as 5913 ;; a "quoted" string. 5915 tagged-ext-simple = sequence-set / number / number64 5917 tagged-ext-val = tagged-ext-simple / 5918 "(" [tagged-ext-comp] ")" 5920 text = 1*TEXT-CHAR 5922 TEXT-CHAR = 5924 time = 2DIGIT ":" 2DIGIT ":" 2DIGIT 5925 ; Hours minutes seconds 5927 uid = "UID" SP 5928 (copy / move / fetch / search / store / uid-expunge) 5929 ; Unique identifiers used instead of message 5930 ; sequence numbers 5932 uid-expunge = "EXPUNGE" SP sequence-set 5933 ; Unique identifiers used instead of message 5934 ; sequence numbers 5936 uid-set = (uniqueid / uid-range) *("," uid-set) 5938 uid-range = (uniqueid ":" uniqueid) 5939 ; two uniqueid values and all values 5940 ; between these two regards of order. 5941 ; Example: 2:4 and 4:2 are equivalent. 5943 uniqueid = nz-number 5944 ; Strictly ascending 5946 unsubscribe = "UNSUBSCRIBE" SP mailbox 5948 userid = astring 5950 UTF8-2 = 5952 UTF8-3 = 5954 UTF8-4 = 5956 x-command = "X" atom 5958 zone = ("+" / "-") 4DIGIT 5959 ; Signed four-digit value of hhmm representing 5960 ; hours and minutes east of Greenwich (that is, 5961 ; the amount that the given time differs from 5962 ; Universal Time). Subtracting the timezone 5963 ; from the given time will give the UT form. 5964 ; The Universal Time zone is "+0000". 5966 10. Author's Note 5968 This document is a revision or rewrite of earlier documents, and 5969 supercedes the protocol specification in those documents: RFC 2060, 5970 RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064. 5972 11. Security Considerations 5974 IMAP4rev2 protocol transactions, including electronic mail data, are 5975 sent in the clear over the network unless protection from snooping is 5976 negotiated. This can be accomplished either by the use of IMAPS 5977 service, STARTTLS command, negotiated privacy protection in the 5978 AUTHENTICATE command, or some other protection mechanism. 5980 11.1. STARTTLS Security Considerations 5982 IMAP client and server implementations MUST comply with relevant TLS 5983 recommendations from [RFC8314]. Additionally, when using TLS 1.2, 5984 IMAP implementations MUST implement 5985 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 cipher suite, and SHOULD 5986 implement the TLS_RSA_WITH_AES_128_CBC_SHA [TLS] cipher suite. This 5987 is important as it assures that any two compliant implementations can 5988 be configured to interoperate. Other TLS cipher suites recommended 5989 in RFC 7525 are RECOMMENDED: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 5990 TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 and 5991 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384. All other cipher suites are 5992 OPTIONAL. Note that this is a change from section 2.1 of [IMAP-TLS]. 5994 During the [TLS] negotiation, the client MUST check its understanding 5995 of the server hostname against the server's identity as presented in 5996 the server Certificate message, in order to prevent man-in-the-middle 5997 attacks. This procedure is described in [RFC7817]. 5999 Both the client and server MUST check the result of the STARTTLS 6000 command and subsequent [TLS] negotiation to see whether acceptable 6001 authentication and/or privacy was achieved. 6003 11.2. COPYUID and APPENDUID response codes 6005 The COPYUID and APPENDUID response codes return information about the 6006 mailbox, which may be considered sensitive if the mailbox has 6007 permissions set that permit the client to COPY or APPEND to the 6008 mailbox, but not SELECT or EXAMINE it. 6010 Consequently, these response codes SHOULD NOT be issued if the client 6011 does not have access to SELECT or EXAMINE the mailbox. 6013 11.3. LIST command and Other Users' namespace 6015 In response to a LIST command containing an argument of the Other 6016 Users' Namespace prefix, a server SHOULD NOT list users that have not 6017 granted list access to their personal mailboxes to the currently 6018 authenticated user. Providing such a list, could compromise security 6019 by potentially disclosing confidential information of who is located 6020 on the server, or providing a starting point of a list of user 6021 accounts to attack. 6023 11.4. Other Security Considerations 6025 A server error message for an AUTHENTICATE command which fails due to 6026 invalid credentials SHOULD NOT detail why the credentials are 6027 invalid. 6029 Use of the LOGIN command sends passwords in the clear. This can be 6030 avoided by using the AUTHENTICATE command with a [SASL] mechanism 6031 that does not use plaintext passwords, by first negotiating 6032 encryption via STARTTLS or some other protection mechanism. 6034 A server implementation MUST implement a configuration that, at the 6035 time of authentication, requires: 6036 (1) The STARTTLS command has been negotiated. 6037 OR 6038 (2) Some other mechanism that protects the session from password 6039 snooping has been provided. 6040 OR 6041 (3) The following measures are in place: 6042 (a) The LOGINDISABLED capability is advertised, and [SASL] mechanisms 6043 (such as PLAIN) using plaintext passwords are NOT advertised in the 6044 CAPABILITY list. 6045 AND 6046 (b) The LOGIN command returns an error even if the password is 6047 correct. 6048 AND 6049 (c) The AUTHENTICATE command returns an error with all [SASL] 6050 mechanisms that use plaintext passwords, even if the password is 6051 correct. 6053 A server error message for a failing LOGIN command SHOULD NOT specify 6054 that the user name, as opposed to the password, is invalid. 6056 A server SHOULD have mechanisms in place to limit or delay failed 6057 AUTHENTICATE/LOGIN attempts. 6059 Additional security considerations are discussed in the section 6060 discussing the AUTHENTICATE and LOGIN commands. 6062 12. IANA Considerations 6064 IANA is requested to update "Service Names and Transport Protocol 6065 Port Numbers" registry as follows: 6067 1. Registration for TCP "imap" port 143 should be updated to point 6068 to this document and RFC 3501. 6070 2. Registration for TCP "imaps" port 993 should be updated to point 6071 to this document, RFC 8314 and RFC 3501. 6073 3. Both UDP port 143 and UDP port 993 should be marked as "Reserved" 6074 in the registry. 6076 Additional IANA actions are specified in subsection of this section. 6078 12.1. Updates to IMAP4 Capabilities registry 6080 IMAP4 capabilities are registered by publishing a standards track or 6081 IESG approved informational or experimental RFC. The registry is 6082 currently located at: http://www.iana.org/assignments/ 6083 imap4-capabilities 6084 As this specification revises the STARTTLS and LOGINDISABLED 6085 extensions previously defined in [IMAP-TLS], IANA is requested to 6086 update registry entries for these 2 extensions to point to this 6087 document. 6089 12.2. GSSAPI/SASL service name 6091 GSSAPI/Kerberos/SASL service names are registered by publishing a 6092 standards track or IESG approved experimental RFC. The registry is 6093 currently located at: http://www.iana.org/assignments/gssapi-service- 6094 names 6096 IANA is requested to update the "imap" service name previously 6097 registered in RFC 3501, to point to this document. 6099 13. References 6101 13.1. Normative References 6103 [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6104 Specifications: ABNF", STD 68, RFC 5234, January 2008, 6105 . 6107 [ANONYMOUS] 6108 Zeilenga, K., "Anonymous Simple Authentication and 6109 Security Layer (SASL) Mechanism", RFC 4505, June 2006, 6110 . 6112 [CHARSET] Freed, N. and J. Postel, "IANA Charset Registration 6113 Procedures", BCP 19, RFC 2978, October 2000, 6114 . 6116 [SCRAM-SHA-256] 6117 Hansen, T., "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS Simple 6118 Authentication and Security Layer (SASL) Mechanisms", 6119 RFC 7677, DOI 10.17487/RFC7677, November 2015, 6120 . 6122 [DISPOSITION] 6123 Troost, R., Dorner, S., and K. Moore, Ed., "Communicating 6124 Presentation Information in Internet Messages: The 6125 Content-Disposition Header Field", RFC 2183, August 1997, 6126 . 6128 [PLAIN] Zeilenga, K., Ed., "The PLAIN Simple Authentication and 6129 Security Layer (SASL) Mechanism", RFC 4616, August 2006, 6130 . 6132 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6133 Requirement Levels", BCP 14, RFC 2119, 6134 DOI 10.17487/RFC2119, March 1997, 6135 . 6137 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 6138 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 6139 May 2017, . 6141 [LANGUAGE-TAGS] 6142 Alvestrand, H., "Content Language Headers", RFC 3282, May 6143 2002, . 6145 [LOCATION] 6146 Palme, J., Hopmann, A., and N. Shelness, "MIME 6147 Encapsulation of Aggregate Documents, such as HTML 6148 (MHTML)", RFC 2557, March 1999, 6149 . 6151 [MD5] Myers, J. and M. Rose, "The Content-MD5 Header Field", 6152 RFC 1864, October 1995, 6153 . 6155 [MIME-HDRS] 6156 Moore, K., "MIME (Multipurpose Internet Mail Extensions) 6157 Part Three: Message Header Extensions for Non-ASCII Text", 6158 RFC 2047, November 1996, 6159 . 6161 [MIME-IMB] 6162 Freed, N. and N. Borenstein, "Multipurpose Internet Mail 6163 Extensions (MIME) Part One: Format of Internet Message 6164 Bodies", RFC 2045, November 1996, 6165 . 6167 [MIME-IMT] 6168 Freed, N. and N. Borenstein, "Multipurpose Internet Mail 6169 Extensions (MIME) Part Two: Media Types", RFC 2046, 6170 November 1996, . 6172 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 6173 Word Extensions: Character Sets, Languages, and 6174 Continuations", RFC 2231, DOI 10.17487/RFC2231, November 6175 1997, . 6177 [RFC-5322] 6178 Resnick, P., Ed., "Internet Message Format", RFC 5322, 6179 October 2008, . 6181 [SASL] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple 6182 Authentication and Security Layer (SASL)", RFC 4422, June 6183 2006, . 6185 [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security 6186 (TLS) Protocol Version 1.2", RFC 5246, August 2008, 6187 . 6189 [UTF-7] Goldsmith, D. and M. Davis, "UTF-7 A Mail-Safe 6190 Transformation Format of Unicode", RFC 2152, May 1997, 6191 . 6193 [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 6194 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 6195 2003, . 6197 [MULTIAPPEND] 6198 Crispin, M., "Internet Message Access Protocol (IMAP) - 6199 MULTIAPPEND Extension", RFC 3502, March 2003, 6200 . 6202 [NET-UNICODE] 6203 Klensin, J. and M. Padlipsky, "Unicode Format for Network 6204 Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, 6205 . 6207 [I18N-HDRS] 6208 Yang, A., Steele, S., and N. Freed, "Internationalized 6209 Email Headers", RFC 6532, DOI 10.17487/RFC6532, February 6210 2012, . 6212 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 6213 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 6214 . 6216 [RFC7817] Melnikov, A., "Updated Transport Layer Security (TLS) 6217 Server Identity Check Procedure for Email-Related 6218 Protocols", RFC 7817, DOI 10.17487/RFC7817, March 2016, 6219 . 6221 [RFC8098] Hansen, T., Ed. and A. Melnikov, Ed., "Message Disposition 6222 Notification", STD 85, RFC 8098, DOI 10.17487/RFC8098, 6223 February 2017, . 6225 [RFC8314] Moore, K. and C. Newman, "Cleartext Considered Obsolete: 6226 Use of Transport Layer Security (TLS) for Email Submission 6227 and Access", RFC 8314, DOI 10.17487/RFC8314, January 2018, 6228 . 6230 [IMAP-IMPLEMENTATION] 6231 Leiba, B., "IMAP4 Implementation Recommendations", 6232 RFC 2683, September 1999, 6233 . 6235 [IMAP-MULTIACCESS] 6236 Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", 6237 RFC 2180, July 1997, 6238 . 6240 13.2. Informative References (related protocols) 6242 [RFC5258] Leiba, B. and A. Melnikov, "Internet Message Access 6243 Protocol version 4 - LIST Command Extensions", RFC 5258, 6244 DOI 10.17487/RFC5258, June 2008, 6245 . 6247 [RFC2193] Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193, 6248 DOI 10.17487/RFC2193, September 1997, 6249 . 6251 [RFC3348] Gahrns, M. and R. Cheng, "The Internet Message Action 6252 Protocol (IMAP4) Child Mailbox Extension", RFC 3348, 6253 DOI 10.17487/RFC3348, July 2002, 6254 . 6256 [RFC7888] Melnikov, A., Ed., "IMAP4 Non-synchronizing Literals", 6257 RFC 7888, DOI 10.17487/RFC7888, May 2016, 6258 . 6260 [IMAP-DISC] 6261 Melnikov, A., Ed., "Synchronization Operations for 6262 Disconnected IMAP4 Clients", RFC 4549, June 2006, 6263 . 6265 [IMAP-I18N] 6266 Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet 6267 Message Access Protocol Internationalization", RFC 5255, 6268 DOI 10.17487/RFC5255, June 2008, 6269 . 6271 [IMAP-MODEL] 6272 Crispin, M., "Distributed Electronic Mail Models in 6273 IMAP4", RFC 1733, December 1994, 6274 . 6276 [IMAP-UTF-8] 6277 Resnick, P., Ed., Newman, C., Ed., and S. Shen, Ed., "IMAP 6278 Support for UTF-8", RFC 6855, DOI 10.17487/RFC6855, March 6279 2013, . 6281 [SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, 6282 October 2008, . 6284 [RFC3516] Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516, 6285 DOI 10.17487/RFC3516, April 2003, 6286 . 6288 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 6289 RFC 4314, December 2005, 6290 . 6292 [RFC2087] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January 6293 1997, . 6295 [IMAP-URL] 6296 Melnikov, A., Ed. and C. Newman, "IMAP URL Scheme", 6297 RFC 5092, DOI 10.17487/RFC5092, November 2007, 6298 . 6300 13.3. Informative References (historical aspects of IMAP and related 6301 protocols) 6303 [IMAP-COMPAT] 6304 Crispin, M., "IMAP4 Compatibility with IMAP2bis", 6305 RFC 2061, December 1996, 6306 . 6308 [IMAP-HISTORICAL] 6309 Crispin, M., "IMAP4 Compatibility with IMAP2 and 6310 IMAP2bis", RFC 1732, December 1994, 6311 . 6313 [IMAP-OBSOLETE] 6314 Crispin, M., "Internet Message Access Protocol - Obsolete 6315 Syntax", RFC 2062, December 1996, 6316 . 6318 [IMAP2] Crispin, M., "Interactive Mail Access Protocol: Version 6319 2", RFC 1176, August 1990, 6320 . 6322 [RFC-822] Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET 6323 TEXT MESSAGES", STD 11, RFC 822, August 1982, 6324 . 6326 [RFC-821] Postel, J., "Simple Mail Transfer Protocol", STD 10, 6327 RFC 821, August 1982, 6328 . 6330 [IMAP-TLS] 6331 Newman, C., "Using TLS with IMAP, POP3 and ACAP", 6332 RFC 2595, June 1999, 6333 . 6335 Appendix A. Backward compatibility with IMAP4rev1 6337 An implementation that wants to remain compatible with IMAP4rev1 can 6338 advertise both IMAP4rev1 and IMAP4rev2 in its CAPABILITY response/ 6339 response code. While some IMAP4rev1 responses were removed in 6340 IMAP4rev2, their presence will not break IMAP4rev2-only clients. 6342 If both IMAP4rev1 and IMAP4rev2 are advertised, an IMAP client that 6343 wants to use IMAP4rev2 MUST issue an "ENABLE IMAP4rev2" command. 6345 Servers advertising both IMAP4rev1 and IMAP4rev2 SHOULD NOT generate 6346 UTF-8 quoted strings unless the client has issued "ENABLE IMAP4rev2". 6347 Consider implementation of mechanisms described or referenced in 6348 [IMAP-UTF-8] to achieve this goal. 6350 Servers advertising both IMAP4rev1 and IMAP4rev2, and clients 6351 intending to be compatible with IMAP4rev1 servers MUST be compatible 6352 with the international mailbox naming convention described in the 6353 following subsection. 6355 A.1. Mailbox International Naming Convention for compatibility with 6356 IMAP4rev1 6358 Support for the Mailbox International Naming Convention described in 6359 this section is not required for IMAP4rev2-only clients and servers. 6361 By convention, international mailbox names in IMAP4rev1 are specified 6362 using a modified version of the UTF-7 encoding described in [UTF-7]. 6363 Modified UTF-7 may also be usable in servers that implement an 6364 earlier version of this protocol. 6366 In modified UTF-7, printable US-ASCII characters, except for "&", 6367 represent themselves; that is, characters with octet values 0x20-0x25 6368 and 0x27-0x7e. The character "&" (0x26) is represented by the two- 6369 octet sequence "&-". 6371 All other characters (octet values 0x00-0x1f and 0x7f-0xff) are 6372 represented in modified BASE64, with a further modification from 6373 [UTF-7] that "," is used instead of "/". Modified BASE64 MUST NOT be 6374 used to represent any printing US-ASCII character which can represent 6375 itself. Only characters inside the modified BASE64 alphabet are 6376 permitted in modified BASE64 text. 6378 "&" is used to shift to modified BASE64 and "-" to shift back to US- 6379 ASCII. There is no implicit shift from BASE64 to US-ASCII, and null 6380 shifts ("-&" while in BASE64; note that "&-" while in US-ASCII means 6381 "&") are not permitted. However, all names start in US-ASCII, and 6382 MUST end in US-ASCII; that is, a name that ends with a non-ASCII 6383 ISO-10646 character MUST end with a "-"). 6385 The purpose of these modifications is to correct the following 6386 problems with UTF-7: 6388 1. UTF-7 uses the "+" character for shifting; this conflicts with 6389 the common use of "+" in mailbox names, in particular USENET 6390 newsgroup names. 6392 2. UTF-7's encoding is BASE64 which uses the "/" character; this 6393 conflicts with the use of "/" as a popular hierarchy delimiter. 6395 3. UTF-7 prohibits the unencoded usage of "\"; this conflicts with 6396 the use of "\" as a popular hierarchy delimiter. 6398 4. UTF-7 prohibits the unencoded usage of "~"; this conflicts with 6399 the use of "~" in some servers as a home directory indicator. 6401 5. UTF-7 permits multiple alternate forms to represent the same 6402 string; in particular, printable US-ASCII characters can be 6403 represented in encoded form. 6405 Although modified UTF-7 is a convention, it establishes certain 6406 requirements on server handling of any mailbox name with an embedded 6407 "&" character. In particular, server implementations MUST preserve 6408 the exact form of the modified BASE64 portion of a modified UTF-7 6409 name and treat that text as case-sensitive, even if names are 6410 otherwise case-insensitive or case-folded. 6412 Server implementations SHOULD verify that any mailbox name with an 6413 embedded "&" character, used as an argument to CREATE, is: in the 6414 correctly modified UTF-7 syntax, has no superfluous shifts, and has 6415 no encoding in modified BASE64 of any printing US-ASCII character 6416 which can represent itself. However, client implementations MUST NOT 6417 depend upon the server doing this, and SHOULD NOT attempt to create a 6418 mailbox name with an embedded "&" character unless it complies with 6419 the modified UTF-7 syntax. 6421 Server implementations which export a mail store that does not follow 6422 the modified UTF-7 convention MUST convert to modified UTF-7 any 6423 mailbox name that contains either non-ASCII characters or the "&" 6424 character. 6426 For example, here is a mailbox name which mixes English, Chinese, 6427 and Japanese text: ~peter/mail/&U,BTFw-/&ZeVnLIqe- 6429 For example, the string "&Jjo!" is not a valid mailbox name 6430 because it does not contain a shift to US-ASCII before the "!". 6431 The correct form is "&Jjo-!". The string "&U,BTFw-&ZeVnLIqe-" is 6432 not permitted because it contains a superfluous shift. The 6433 correct form is "&U,BTF2XlZyyKng-". 6435 Appendix B. Backward compatibility with BINARY extension 6437 IMAP4rev2 is incorporates subset of functionality provided by the 6438 BINARY extension [RFC3516], in particular it includes additional 6439 FETCH items (BINARY, BINARY.PEEK and BINARY.SIZE), but not extensions 6440 to the APPEND command. IMAP4rev2 implementations that supports full 6441 RFC 3516 functionality need to also advertise the BINARY token in the 6442 CAPABILITY response. 6444 Appendix C. Changes from RFC 3501 / IMAP4rev1 6446 The following is the plan for remaining changes. The plan might 6447 change over time. 6449 1. Fold in the following extensions/RFC: RFC 5530 (IMAP Response 6450 Codes, done), UIDPLUS (done), ENABLE (done), ESEARCH (done), 6451 SPECIAL-USE (list of new mailbox attributes is done), LITERAL- 6452 (done), NAMESPACE (done), SASL-IR (done), IDLE (done), MOVE 6453 (done). 6455 2. Add CLOSED response code (from CONDSTORE) - done 6457 3. Add support for $MDNSent and $Forwarded IMAP keywords - done. 6458 Add more examples showing their use? Also add other keywords 6459 like $Phishing, $Junk, $NonJunk? 6461 4. Require all unsolicited FETCH updates to include UID - done. 6463 5. Update recommendations on TLS ciphers to match UTA WG work (as 6464 per RFC 8314, RFC 7525 and RFC 7817) - done. 6466 6. Possibly fold in the following extensions/RFC: Base LIST- 6467 EXTENDED syntax plus deprecate LSUB (replace it with LIST 6468 \Subscribed) minus the requirement to support multiple list 6469 patterns, STATUS-in-LIST, SEARCHRES, BINARY (only the FETCH 6470 changes on leaf body part and make APPEND related ones optional. 6471 See the mailing list discussion) - done. 6473 7. Add STATUS SIZE (total mailbox size) - done Add STATUS DELETED 6474 (number of messages with \Deleted flag set)? Or DELETEDSIZE? 6476 8. Deprecate features: What should we do with NEW search key (which 6477 implies RECENT): deprecate it or just redefine it to ignore 6478 RECENT state? 6480 9. Drop UTF-7, all mailboxes are always in UTF-8 - done. 6482 10. Revise IANA registration of IMAP extensions and give advice on 6483 use of "X-" convention. 6485 11. Allow word-based searching (as per Chris Newman)? Need to 6486 discuss header field search, where exact/substring match is 6487 still required for interoperability. 6489 The following changes since RFC 3501 were done so far: 6491 1. Folded in IMAP UNSELECT (RFC 3691), UIDPLUS (RFC 4315), ESEARCH 6492 (RFC 4731), ENABLE (RFC 5161), IDLE (RFC 2177), SASL-IR (RFC 6493 4959) and MOVE (RFC 6851) extensions. Also folded RFC 5530 and 6494 FETCH side of the BINARY extension (RFC 3516). 6496 2. Clarified that server should decode parameter value 6497 continuations as described in [RFC2231]. This requirement was 6498 hidden in RFC 2231 itself. 6500 3. SEARCH command now requires to return ESEARCH response (SEARCH 6501 response is now deprecated). 6503 4. Added CLOSED response code from RFC 7162. 6505 5. Updated to use modern TLS-related recommendations as per RFC 6506 8314, RFC 7817, RFC 7525. 6508 6. For future extensibility extended ABNF for tagged-ext-simple to 6509 allow for bare number64. 6511 7. Added SHOULD level requirement on IMAP servers to support 6512 $MDNSent and $Forwarded keywords. 6514 8. Added STATUS SIZE. 6516 9. Mailbox names and message headers now allow for UTF-8. Support 6517 for Modified UTF-7 in mailbox names is not required, unless 6518 compatibility with IMAP4rev1 is desired. 6520 10. UNSEEN response code on SELECT/EXAMINE is now deprecated. 6522 11. RECENT response on SELECT/EXAMINE, \Recent flag, RECENT STATUS 6523 item are now deprecated. 6525 12. Clarified that the server doesn't need to send a new 6526 PERMANENTFLAGS response code when a new keyword was successfully 6527 added and the server advertised \* earlier for the same mailbox. 6529 13. Removed the CHECK command. Clients should use NOOP instead. 6531 14. RFC822, RFC822.HEADER and RFC822.TEXT FETCH data items are 6532 deprecated, but supported in this document. 6534 15. Replaced DIGEST-MD5 SASL mechanism with SCRAM-SHA-256. DIGEST- 6535 MD5 was deprecated. 6537 16. LSUB command was deprecated. Clients should use LIST 6538 (SUBSCRIBED) instead. 6540 Appendix D. Acknowledgement 6542 Earlier versions of this document were edited by Mark Crispin. 6543 Sadly, he is no longer available to help with this work. Editors of 6544 this revisions are hoping that Mark would have approved. 6546 Chris Newman has contributed text on I18N and use of UTF-8 in 6547 messages and mailbox names. 6549 Thank you to Tony Hansen for helping with the index generation. 6550 Thank you to Timo Sirainen, Bron Gondwana and Arnt Gulbrandsen for 6551 extensive feedback. 6553 This document incorporate text from RFC 4315, RFC 4466, RFC 4731, RFC 6554 5161, RFC 6154 so work done by authors/editors of these documents is 6555 appreciated. 6557 Index 6559 $ 6560 $Forwarded (predefined flag) 12 6561 $MDNSent (predefined flag) 12 6563 + 6564 +FLAGS 80 6565 +FLAGS.SILENT 80 6567 - 6568 -FLAGS 80 6569 -FLAGS.SILENT 80 6571 A 6572 ALERT (response code) 87 6573 ALL (fetch item) 75 6574 ALL (search key) 72 6575 ALL (search result option) 70 6576 ALREADYEXISTS (response code) 87 6577 ANSWERED (search key) 72 6578 APPEND (command) 63 6579 APPENDUID (response code) 87 6580 AUTHENTICATE (command) 28 6581 AUTHENTICATIONFAILED (response code) 88 6582 AUTHORIZATIONFAILED (response code) 88 6584 B 6585 BAD (response) 95 6586 BADCHARSET (response code) 88 6587 BCC (search key) 72 6588 BEFORE (search key) 72 6589 BINARY.PEEK[]<> (fetch item) 76 6590 BINARY.SIZE[] (fetch item) 76 6591 BINARY.SIZE[] (fetch result) 104 6592 BINARY[]<> (fetch result) 104 6593 BINARY[]<> (fetch item) 75 6594 BODY (fetch item) 76 6595 BODY (fetch result) 105 6596 BODY (search key) 72 6597 BODY.PEEK[
]<> (fetch item) 78 6598 BODYSTRUCTURE (fetch item) 78 6599 BODYSTRUCTURE (fetch result) 105 6600 BODY[
]<> (fetch result) 105 6601 BODY[
]<> (fetch item) 76 6602 BYE (response) 95 6603 Body Structure (message attribute) 13 6605 C 6606 CANNOT (response code) 88 6607 CAPABILITY (command) 24 6608 CAPABILITY (response code) 88 6609 CAPABILITY (response) 96 6610 CC (search key) 72 6611 CLIENTBUG (response code) 89 6612 CLOSE (command) 68 6613 CLOSED (response code) 89 6614 CONTACTADMIN (response code) 89 6615 COPY (command) 80 6616 COPYUID (response code) 89 6617 CORRUPTION (response code) 90 6618 COUNT (search result option) 71 6619 CREATE (command) 36 6621 D 6622 DELETE (command) 37 6623 DELETED (search key) 72 6624 DRAFT (search key) 72 6626 E 6627 ENABLE (command) 32 6628 ENVELOPE (fetch item) 78 6629 ENVELOPE (fetch result) 108 6630 ESEARCH (response) 101 6631 EXAMINE (command) 35 6632 EXPIRED (response code) 90 6633 EXPUNGE (command) 69 6634 EXPUNGE (response) 103 6635 EXPUNGEISSUED (response code) 90 6636 Envelope Structure (message attribute) 13 6638 F 6639 FAST (fetch item) 75 6640 FETCH (command) 75 6641 FETCH (response) 104 6642 FLAGGED (search key) 72 6643 FLAGS (fetch item) 78 6644 FLAGS (fetch result) 109 6645 FLAGS (response) 102 6646 FLAGS (store command data item) 79 6647 FLAGS.SILENT (store command data item) 79 6648 FROM (search key) 72 6649 FULL (fetch item) 75 6650 Flags (message attribute) 11 6652 H 6653 HEADER (part specifier) 76 6654 HEADER (search key) 72 6655 HEADER.FIELDS (part specifier) 76 6656 HEADER.FIELDS.NOT (part specifier) 76 6658 I 6659 IDLE (command) 66 6660 INTERNALDATE (fetch item) 78 6661 INTERNALDATE (fetch result) 109 6662 INUSE (response code) 90 6663 Internal Date (message attribute) 12 6665 K 6666 KEYWORD (search key) 72 6667 Keyword (type of flag) 12 6669 L 6670 LARGER (search key) 72 6671 LIMIT (response code) 91 6672 LIST (command) 41 6673 LIST (response) 97 6674 LOGOUT (command) 26 6676 M 6677 MAX (search result option) 70 6678 MAY (specification requirement term) 5 6679 MESSAGES (status item) 63 6680 MIME (part specifier) 77 6681 MIN (search result option) 70 6682 MOVE (command) 81 6683 MUST (specification requirement term) 5 6684 MUST NOT (specification requirement term) 5 6685 Message Sequence Number (message attribute) 11 6687 N 6688 NAMESPACE (command) 57 6689 NAMESPACE (response) 101 6690 NEW (search key) 72 6691 NO (response) 94 6692 NONEXISTENT (response code) 91 6693 NOOP (command) 25 6694 NOPERM (response code) 91 6695 NOT (search key) 73 6696 NOT RECOMMENDED (specification requirement term) 5 6698 O 6699 OK (response) 94 6700 ON (search key) 73 6701 OPTIONAL (specification requirement term) 5 6702 OR (search key) 73 6703 OVERQUOTA (response code) 91 6705 P 6706 PARSE (response code) 92 6707 PERMANENTFLAGS (response code) 92 6708 PREAUTH (response) 95 6709 PRIVACYREQUIRED (response code) 92 6710 Permanent Flag (class of flag) 12 6711 Predefined keywords 12 6713 R 6714 READ-ONLY (response code) 92 6715 READ-WRITE (response code) 92 6716 RECOMMENDED (specification requirement term) 5 6717 RENAME (command) 38 6718 REQUIRED (specification requirement term) 5 6719 RFC822 (fetch item) 78 6720 RFC822 (fetch result) 109 6721 RFC822.HEADER (fetch item) 78 6722 RFC822.HEADER (fetch result) 109 6723 RFC822.SIZE (fetch item) 79 6724 RFC822.SIZE (fetch result) 109 6725 RFC822.TEXT (fetch item) 79 6726 RFC822.TEXT (fetch result) 109 6728 S 6729 SEARCH (command) 69 6730 SEEN (search key) 73 6731 SELECT (command) 34 6732 SENTBEFORE (search key) 73 6733 SENTON (search key) 73 6734 SENTSINCE (search key) 73 6735 SERVERBUG (response code) 92 6736 SHOULD (specification requirement term) 5 6737 SHOULD NOT (specification requirement term) 5 6738 SINCE (search key) 73 6739 SIZE (status item) 63 6740 SMALLER (search key) 73 6741 STARTTLS (command) 27 6742 STATUS (command) 62 6743 STATUS (response) 101 6744 STORE (command) 79 6745 SUBJECT (search key) 73 6746 SUBSCRIBE (command) 40 6747 Session Flag (class of flag) 12 6748 System Flag (type of flag) 11 6750 T 6751 TEXT (part specifier) 76 6752 TEXT (search key) 73 6753 TO (search key) 73 6754 TRYCREATE (response code) 93 6756 U 6757 UID (command) 83 6758 UID (fetch item) 79 6759 UID (fetch result) 109 6760 UID (search key) 73 6761 UIDNEXT (response code) 93 6762 UIDNEXT (status item) 63 6763 UIDNOTSTICKY (response code) 93 6764 UIDVALIDITY (response code) 93 6765 UIDVALIDITY (status item) 63 6766 UNANSWERED (search key) 73 6767 UNAVAILABLE (response code) 93 6768 UNDELETED (search key) 73 6769 UNDRAFT (search key) 73 6770 UNFLAGGED (search key) 73 6771 UNKEYWORD (search key) 74 6772 UNKNOWN-CTE (response code) 93 6773 UNSEEN (search key) 74 6774 UNSEEN (status item) 63 6775 UNSELECT (command) 68 6776 UNSUBSCRIBE (command) 41 6777 Unique Identifier (UID) (message attribute) 9 6779 X 6780 X (command) 85 6782 [ 6783 [RFC-5322] Size (message attribute) 13 6785 \ 6786 \All (mailbox name attribute) 99 6787 \Answered (system flag) 11 6788 \Archive (mailbox name attribute) 99 6789 \Deleted (system flag) 11 6790 \Draft (system flag) 12 6791 \Drafts (mailbox name attribute) 99 6792 \Flagged (mailbox name attribute) 100 6793 \Flagged (system flag) 11 6794 \HasChildren (mailbox name attribute) 98 6795 \HasNoChildren (mailbox name attribute) 98 6796 \Junk (mailbox name attribute) 100 6797 \Marked (mailbox name attribute) 99 6798 \Noinferiors (mailbox name attribute) 98 6799 \NonExistent (mailbox name attribute) 98 6800 \Noselect (mailbox name attribute) 98 6801 \Recent (system flag) 12 6802 \Remote (mailbox name attribute) 99 6803 \Seen (system flag) 11 6804 \Sent (mailbox name attribute) 100 6805 \Subscribed (mailbox name attribute) 99 6806 \Trash (mailbox name attribute) 100 6807 \Unmarked (mailbox name attribute) 99 6809 Authors' Addresses 6811 Alexey Melnikov (editor) 6812 Isode Ltd 6813 14 Castle Mews 6814 Hampton, Middlesex TW12 2NP 6815 UK 6817 Email: Alexey.Melnikov@isode.com 6819 Barry Leiba (editor) 6820 Huawei Technologies 6822 Phone: +1 646 827 0648 6823 Email: barryleiba@computer.org 6824 URI: http://internetmessagingtechnology.org/