idnits 2.17.1 draft-ietf-appsawg-mdn-3798bis-05.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 : ---------------------------------------------------------------------------- ** There are 14 instances of too long lines in the document, the longest one being 13 characters in excess of 72. -- The draft header indicates that this document obsoletes RFC3798, 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 lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords -- however, there's a paragraph with a matching beginning. Boilerplate error? (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: disposition-modifier-extension Disposition modifiers may be defined in the future by later revisions or extensions to this specification. Disposition value names beginning with "X-" will never be defined as standard values; such names are reserved for experimental use. MDN disposition value names NOT beginning with "X-" MUST be registered with the Internet Assigned Numbers Authority (IANA) and described in a standards-track RFC or an experimental RFC approved by the IESG. (See Section 10 for a registration form.) MDNs with disposition modifier names not understood by the receiving MUA MAY be silently ignored or placed in the user's mailbox without special interpretation. They MUST not cause any error message to be sent to the sender of the MDN. == 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 (December 2, 2015) is 3061 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: 'FWS' on line 1004 -- Looks like a reference, but probably isn't: 'CFWS' on line 551 ** Obsolete normative reference: RFC 3462 (ref. '6') (Obsoleted by RFC 6522) -- Obsolete informational reference (is this intentional?): RFC 3501 (ref. '13') (Obsoleted by RFC 9051) Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Hansen, Ed. 3 Internet-Draft AT&T Laboratories 4 Obsoletes: 3798 (if approved) A. Melnikov, Ed. 5 Intended status: Standards Track Isode Ltd 6 Expires: June 4, 2016 December 2, 2015 8 Message Disposition Notification 9 draft-ietf-appsawg-mdn-3798bis-05.txt 11 Abstract 13 This memo defines a MIME content-type that may be used by a mail user 14 agent (MUA) or electronic mail gateway to report the disposition of a 15 message after it has been successfully delivered to a recipient. 16 This content-type is intended to be machine-processable. Additional 17 message header fields are also defined to permit Message Disposition 18 Notifications (MDNs) to be requested by the sender of a message. The 19 purpose is to extend Internet Mail to support functionality often 20 found in other messaging systems, such as X.400 and the proprietary 21 "LAN-based" systems, and often referred to as "read receipts," 22 "acknowledgements", or "receipt notifications." The intention is to 23 do this while respecting privacy concerns, which have often been 24 expressed when such functions have been discussed in the past. 26 Because many messages are sent between the Internet and other 27 messaging systems (such as X.400 or the proprietary "LAN-based" 28 systems), the MDN protocol is designed to be useful in a multi- 29 protocol messaging environment. To this end, the protocol described 30 in this memo provides for the carriage of "foreign" addresses, in 31 addition to those normally used in Internet Mail. Additional 32 attributes may also be defined to support "tunneling" of foreign 33 notifications through Internet Mail. 35 Status of This Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF). Note that other groups may also distribute 42 working documents as Internet-Drafts. The list of current Internet- 43 Drafts is at http://datatracker.ietf.org/drafts/current/. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 This Internet-Draft will expire on June 4, 2016. 51 Copyright Notice 53 Copyright (c) 2015 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (http://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 This document may contain material from IETF Documents or IETF 67 Contributions published or made publicly available before November 68 10, 2008. The person(s) controlling the copyright in some of this 69 material may not have granted the IETF Trust the right to allow 70 modifications of such material outside the IETF Standards Process. 71 Without obtaining an adequate license from the person(s) controlling 72 the copyright in such materials, this document may not be modified 73 outside the IETF Standards Process, and derivative works of it may 74 not be created outside the IETF Standards Process, except to format 75 it for publication as an RFC or to translate it into languages other 76 than English. 78 Table of Contents 80 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 81 1.1. Purposes . . . . . . . . . . . . . . . . . . . . . . . . 3 82 1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 4 83 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 84 2. Requesting Message Disposition Notifications . . . . . . . . 5 85 2.1. The Disposition-Notification-To Header . . . . . . . . . 5 86 2.2. The Disposition-Notification-Options Header . . . . . . . 7 87 2.3. The Original-Recipient Header Field . . . . . . . . . . . 8 88 2.4. Use with the Message/Partial Content Type . . . . . . . . 8 89 3. Format of a Message Disposition Notification . . . . . . . . 9 90 3.1. The message/disposition-notification content-type . . . . 10 91 3.2. Message/disposition-notification Fields . . . . . . . . . 12 92 3.3. Extension-fields . . . . . . . . . . . . . . . . . . . . 18 93 4. Timeline of events . . . . . . . . . . . . . . . . . . . . . 18 94 5. Conformance and Usage Requirements . . . . . . . . . . . . . 19 95 6. Security Considerations . . . . . . . . . . . . . . . . . . . 20 96 6.1. Forgery . . . . . . . . . . . . . . . . . . . . . . . . . 20 97 6.2. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 20 98 6.3. Non-Repudiation . . . . . . . . . . . . . . . . . . . . . 21 99 6.4. Mail Bombing . . . . . . . . . . . . . . . . . . . . . . 22 100 7. Collected ABNF Grammar . . . . . . . . . . . . . . . . . . . 22 101 8. Guidelines for Gatewaying MDNs . . . . . . . . . . . . . . . 24 102 8.1. Gatewaying from other mail systems to MDNs . . . . . . . 24 103 8.2. Gatewaying from MDNs to other mail systems . . . . . . . 24 104 8.3. Gatewaying of MDN-requests to other mail systems . . . . 25 105 9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 106 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 107 10.1. Disposition-Notification-Options header field 108 disposition-notification-parameter names . . . . . . . . 27 109 10.2. Disposition modifier names . . . . . . . . . . . . . . . 27 110 10.3. MDN extension field names . . . . . . . . . . . . . . . 28 111 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 112 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 113 12.1. Normative References . . . . . . . . . . . . . . . . . . 28 114 12.2. Informative References . . . . . . . . . . . . . . . . . 29 115 Appendix A. Changes from RFC 3798 . . . . . . . . . . . . . . . 30 116 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31 118 1. Introduction 120 This memo defines a RFC-MIME-MEDIA [4] content-type for message 121 disposition notifications (MDNs). An MDN can be used to notify the 122 sender of a message of any of several conditions that may occur after 123 successful delivery, such as display of the message contents, 124 printing of the message, deletion (without display) of the message, 125 or the recipient's refusal to provide MDNs. The "message/ 126 disposition-notification" content-type defined herein is intended for 127 use within the framework of the "multipart/report" content type 128 defined in RFC-REPORT [6]. 130 This memo defines the format of the notifications and the RFC-MSGFMT 131 [2] header fields used to request them. 133 This memo is an update to RFC 3798 and is intended to be published at 134 Internet Standard Level. 136 This memo is currently marked with the 'pre5378Trust200902' IPR 137 statements until a release has been obtained from all previous 138 authors and editors of this text. 140 1.1. Purposes 142 The MDNs defined in this memo are expected to serve several purposes: 144 a. Inform human beings of the disposition of messages after 145 successful delivery, in a manner that is largely independent of 146 human language; 148 b. Allow mail user agents to keep track of the disposition of 149 messages sent, by associating returned MDNs with earlier message 150 transmissions; 152 c. Convey disposition notification requests and disposition 153 notifications between Internet Mail and "foreign" mail systems 154 via a gateway; 156 d. Allow "foreign" notifications to be tunneled through a MIME- 157 capable message system and back into the original messaging 158 system that issued the original notification, or even to a third 159 messaging system; 161 e. Allow language-independent, yet reasonably precise, indications 162 of the disposition of a message to be delivered. 164 1.2. Requirements 166 These purposes place the following constraints on the notification 167 protocol: 169 a. It must be readable by humans, and must be machine-parsable. 171 b. It must provide enough information to allow message senders (or 172 their user agents) to unambiguously associate an MDN with the 173 message that was sent and the original recipient address for 174 which the MDN was issued (if such information is available), even 175 if the message was forwarded to another recipient address. 177 c. It must also be able to describe the disposition of a message 178 independent of any particular human language or of the 179 terminology of any particular mail system. 181 d. The specification must be extensible in order to accommodate 182 future requirements. 184 1.3. Terminology 186 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 187 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 188 document are to be interpreted as described in RFC-KEYWORDS [9]. 190 All syntax descriptions use the ABNF specified by RFC-MSGFMT [2], in 191 which the lexical tokens (used below) are defined: "CRLF", "FWS", 192 "CFWS", "field-name", "mailbox-list", "msg-id", and "text". The 193 following lexical tokens are defined in RFC-SMTP [1]: "atom". 195 2. Requesting Message Disposition Notifications 197 Message disposition notifications are requested by including a 198 Disposition-Notification-To header field in the message containing 199 one or more addresses specifying where dispositions should be sent. 200 Further information to be used by the recipient's MUA in generating 201 the MDN may be provided by also including Original-Recipient and/or 202 Disposition-Notification-Options header fields in the message. 204 2.1. The Disposition-Notification-To Header 206 A request for the receiving user agent to issue message disposition 207 notifications is made by placing a Disposition-Notification-To header 208 field into the message. The syntax of the header field is 210 mdn-request-header = "Disposition-Notification-To" ":" mailbox-list CRLF 212 The presence of a Disposition-Notification-To header field in a 213 message is merely a request for an MDN. The recipients' user agents 214 are always free to silently ignore such a request. 216 An MDN MUST NOT itself have a Disposition-Notification-To header 217 field. An MDN MUST NOT be generated in response to an MDN. 219 A user agent MUST NOT issue more than one MDN on behalf of each 220 particular recipient. That is, once an MDN has been issued on behalf 221 of a recipient, no further MDNs may be issued on behalf of that 222 recipient by the same user agent, even if another disposition is 223 performed on the message. However, if a message is forwarded, an MDN 224 may have been issued for the recipient doing the forwarding and the 225 recipient of the forwarded message may also cause an MDN to be 226 generated. 228 It is also possible that if the same message is being accessed by 229 multiple user agents (for example using POP3), then multiple 230 dispositions might be generated for the same recipient. User agents 231 SHOULD laverage support in the underlying message access protocol to 232 prevent multiple MDNs from being generated. In particular, when the 233 user agent is accessing the message using RFC-IMAP [13], it SHOULD 234 implement the procedures specified in RFC-IMAP-MDN [10]. 236 While Internet standards normally do not specify the behavior of user 237 interfaces, it is strongly recommended that the user agent obtain the 238 user's consent before sending an MDN. This consent could be obtained 239 for each message through some sort of prompt or dialog box, or 240 globally through the user's setting of a preference. 242 MDNs SHOULD NOT be sent automatically if the address in the 243 Disposition-Notification-To header field differs from the address in 244 the Return-Path header field (see RFC-MSGFMT [2]). In this case, 245 confirmation from the user SHOULD be obtained, if possible. If 246 obtaining consent is not possible (e.g., because the user is not 247 online at the time), then an MDN SHOULD NOT be sent. 249 Confirmation from the user SHOULD be obtained (or no MDN sent) if 250 there is no Return-Path header field in the message, or if there is 251 more than one distinct address in the Disposition-Notification-To 252 header field. 254 The comparison of the addresses should be done using only the addr- 255 spec (local-part "@" domain) portion, excluding any angle brackets, 256 phrase and route. The comparison MUST be case-sensitive for the 257 local-part and case-insensitive for the domain part. The local-part 258 comparison SHOULD be done after performing local-part 259 canonicalization (i.e. after removing the surrounding double-quote 260 characters, if any, as well as any escaping "\" characters. (See 261 RFC-MSGFMT [2] for more details.) Implementations MAY treat known 262 domain aliases as equivalent for the purpose of comparison. 264 Note that use of subaddressing (see [12]) can result in a failure to 265 match two local-parts and thus result in possible suppression of the 266 MDN. This document doesn't recommend special handling for this case, 267 as the receiving MUA can't reliably know whether or not the sender is 268 using subaddressing. 270 If the message contains more than one Return-Path header field, the 271 implementation may pick one to use for the comparison, or treat the 272 situation as a failure of the comparison. 274 The reason for not automatically sending an MDN if the comparison 275 fails or more than one address is specified is to reduce the 276 possibility of mail loops and of MDNs being used for mail bombing. 278 A message that contains a Disposition-Notification-To header field 279 SHOULD also contain a Message-ID header field as specified in RFC- 280 MSGFMT [2]. This will permit automatic correlation of MDNs with 281 their original messages by user agents. 283 If the request for message disposition notifications for some 284 recipients and not others is desired, two copies of the message 285 should be sent, one with a Disposition-Notification-To header field 286 and one without. Many of the other header fields of the message 287 (e.g., To, Cc) will be the same in both copies. The recipients in 288 the respective message envelopes determine for whom message 289 disposition notifications are requested and for whom they are not. 290 If desired, the Message-ID header field may be the same in both 291 copies of the message. Note that there are other situations (e.g., 292 Bcc) in which it is necessary to send multiple copies of a message 293 with slightly different header fields. The combination of such 294 situations and the need to request MDNs for a subset of all 295 recipients may result in more than two copies of a message being 296 sent, some with a Disposition-Notification-To header field and some 297 without. 299 Messages posted to newsgroups SHOULD NOT have a Disposition- 300 Notification-To header field. 302 2.2. The Disposition-Notification-Options Header 304 Future extensions to this specification may require that information 305 be supplied to the recipient's MUA for additional control over how 306 and what MDNs are generated. The Disposition-Notification-Options 307 header field provides an extensible mechanism for such information. 308 The syntax of this header field is as follows: 310 Disposition-Notification-Options = 311 "Disposition-Notification-Options" ":" [FWS] 312 disposition-notification-parameter-list 313 disposition-notification-parameter-list = 314 disposition-notification-parameter 315 *([FWS] ";" [FWS] disposition-notification-parameter) 316 disposition-notification-parameter = attribute [FWS] "=" 317 [FWS] importance [FWS] "," [FWS] value *([FWS] "," [FWS] value) 318 importance = "required" / "optional" 319 attribute = atom 320 value = word 322 An importance of "required" indicates that interpretation of the 323 disposition-notification-parameter is necessary for proper generation 324 of an MDN in response to this request. An importance of "optional" 325 indicates that an MUA that does not understand the meaning of this 326 disposition-notification-parameter MAY generate an MDN in response 327 anyway, ignoring the value of the disposition-notification-parameter. 329 No disposition-notification-parameter attribute names are defined in 330 this specification. Attribute names may be defined in the future by 331 later revisions or extensions to this specification. Disposition- 332 notification-parameter attribute names beginning with "X-" will never 333 be defined as standard names; such names are reserved for 334 experimental use. disposition-notification-parameter attribute names 335 not beginning with "X-" MUST be registered with the Internet Assigned 336 Numbers Authority (IANA) and described in a standards-track RFC or an 337 experimental RFC approved by the IESG. [[ more work needed here ]] 338 (See Section 10 for a registration form.) 340 2.3. The Original-Recipient Header Field 342 Since electronic mail addresses may be rewritten while the message is 343 in transit, it is useful for the original recipient address to be 344 made available by the delivering MTA. The delivering MTA may be able 345 to obtain this information from the ORCPT parameter of the SMTP RCPT 346 TO command, as defined in RFC-SMTP [1] and RFC-DSN-SMTP [7]. 348 RFC-DSN-SMTP [7] is amended as follows: If the ORCPT information is 349 available, the delivering MTA SHOULD insert an Original-Recipient 350 header field at the beginning of the message (along with the Return- 351 Path header field). The delivering MTA MAY delete any other 352 Original-Recipient header fields that occur in the message. The 353 syntax of this header field is as follows: 355 original-recipient-header = 356 "Original-Recipient" ":" [FWS] address-type [FWS] ";" [FWS] generic-address 358 The address-type and generic-address token are as specified in the 359 description of the Original-Recipient field in Section 3.2.3. 361 The purpose of carrying the original recipient information and 362 returning it in the MDN is to permit automatic correlation of MDNs 363 with the original message on a per-recipient basis. 365 2.4. Use with the Message/Partial Content Type 367 The use of the header fields Disposition-Notification-To, 368 Disposition-Notification-Options, and Original-Recipient with the 369 MIME message/partial content type (RFC-MIME-MEDIA [4]]) requires 370 further definition. 372 When a message is segmented into two or more message/partial 373 fragments, the three header fields mentioned in the above paragraph 374 SHOULD be placed in the "inner" or "enclosed" message (using the 375 terms of RFC-MIME-MEDIA [4]). These header fields SHOULD NOT be used 376 in the header fields of any of the fragments themselves. 378 When the multiple message/partial fragments are reassembled, the 379 following applies. If these header fields occur along with the other 380 header fields of a message/partial fragment message, they pertain to 381 an MDN that will be generated for the fragment. If these header 382 fields occur in the header fields of the "inner" or "enclosed" 383 message (using the terms of RFC-MIME-MEDIA [4]), they pertain to an 384 MDN that will be generated for the reassembled message. 385 Section 5.2.2.1 of RFC-MIME-MEDIA [4]) is amended to specify that, in 386 addition to the header fields specified there, the three header 387 fields described in this specification are to be appended, in order, 388 to the header fields of the reassembled message. Any occurrences of 389 the three header fields defined here in the header fields of the 390 initial enclosing message must not be copied to the reassembled 391 message. 393 3. Format of a Message Disposition Notification 395 A message disposition notification is a MIME message with a top-level 396 content-type of multipart/report (defined in RFC-REPORT [6]). When 397 multipart/report content is used to transmit an MDN: 399 a. The report-type parameter of the multipart/report content is 400 "disposition-notification". 402 b. The first component of the multipart/report contains a human- 403 readable explanation of the MDN, as described in RFC-REPORT [6]. 405 c. The second component of the multipart/report is of content-type 406 message/disposition-notification, described in Section 3.1 of 407 this document. 409 d. If the original message or a portion of the message is to be 410 returned to the sender, it appears as the third component of the 411 multipart/report. The decision of whether or not to return the 412 message or part of the message is up to the MUA generating the 413 MDN. However, in the case of encrypted messages requesting MDNs, 414 encrypted message text MUST be returned, if it is returned at 415 all, only in its original encrypted form. 417 NOTE: For message disposition notifications gatewayed from foreign 418 systems, the header fields of the original message may not be 419 available. In this case, the third component of the MDN may be 420 omitted, or it may contain "simulated" RFC-MSGFMT [2] header fields 421 that contain equivalent information. In particular, it is very 422 desirable to preserve the subject and date fields from the original 423 message. 425 The MDN MUST be addressed (in both the message header field and the 426 transport envelope) to the address(es) from the Disposition- 427 Notification-To header field from the original message for which the 428 MDN is being generated. 430 The From field of the message header field of the MDN MUST contain 431 the address of the person for whom the message disposition 432 notification is being issued. 434 The envelope sender address (i.e., SMTP MAIL FROM) of the MDN MUST be 435 null (<>), specifying that no Delivery Status Notification messages 436 or other messages indicating successful or unsuccessful delivery are 437 to be sent in response to an MDN. 439 A message disposition notification MUST NOT itself request an MDN. 440 That is, it MUST NOT contain a Disposition-Notification-To header 441 field. 443 The Message-ID header field (if present) for an MDN MUST be different 444 from the Message-ID of the message for which the MDN is being issued. 446 A particular MDN describes the disposition of exactly one message for 447 exactly one recipient. Multiple MDNs may be generated as a result of 448 one message submission, one per recipient. However, due to the 449 circumstances described in Section 2.1, MDNs may not be generated for 450 some recipients for which MDNs were requested. 452 3.1. The message/disposition-notification content-type 454 The message/disposition-notification content-type is defined as 455 follows: 457 MIME type name: message 459 MIME subtype name: disposition-notification 461 Optional parameters: none 463 Encoding considerations: "7bit" encoding is sufficient and MUST be 464 used to maintain readability when viewed by non- 465 MIME mail readers. 467 Security considerations: discussed in Section 6 of this memo. 469 (While the 7bit restriction applies to the message/disposition- 470 notification portion of the multipart/report content, it does not 471 apply to the optional third portion of the multipart/report content.) 473 The message/disposition-notification report type for use in the 474 multipart/report is "disposition-notification". 476 The body of a message/disposition-notification consists of one or 477 more "fields" formatted according to the ABNF of RFC-MSGFMT [2] 478 header "fields". The syntax of the message/disposition-notification 479 content is as follows: 481 disposition-notification-content = [ reporting-ua-field CRLF ] 482 [ mdn-gateway-field CRLF ] 483 [ original-recipient-field CRLF ] 484 final-recipient-field CRLF 485 [ original-message-id-field CRLF ] 486 disposition-field CRLF 487 *( failure-field CRLF ) 488 *( error-field CRLF ) 489 *( extension-field CRLF ) 490 extension-field = extension-field-name ":" *([FWS] text) 491 extension-field-name = field-name 493 Note that the order of the above fields is fixed, with the exception 494 of the extension fields. 496 3.1.1. General conventions for fields 498 Since these fields are defined according to the rules of RFC-MSGFMT 499 [2], the same conventions for continuation lines and comments apply. 500 Notification fields may be continued onto multiple lines by beginning 501 each additional line with a SPACE or HTAB. Text that appears in 502 parentheses is considered a comment and not part of the contents of 503 that notification field. Field names are case-insensitive, so the 504 names of notification fields may be spelled in any combination of 505 upper and lower case letters. Comments in notification fields may 506 use the "encoded-word" construct defined in RFC-MIME-HEADER [5]. 508 3.1.2. "*-type" subfields 510 Several fields consist of a "-type" subfield, followed by a semi- 511 colon, followed by "*text". 512 For these fields, the keyword used in the address-type or MTA-type 513 subfield indicates the expected format of the address or MTA-name 514 that follows. 516 The "-type" subfields are defined as follows: 518 a. An "address-type" specifies the format of a mailbox address. For 519 example, Internet Mail addresses use the "rfc822" address-type. 521 address-type = atom 522 atom = 524 b. An "MTA-name-type" specifies the format of a mail transfer agent 525 name. For example, for an SMTP server on an Internet host, the 526 MTA name is the domain name of that host, and the "dns" MTA-name- 527 type is used. 529 mta-name-type = atom 531 Values for address-type and mta-name-type are case-insensitive. 532 Thus, address-type values of "RFC822" and "rfc822" are equivalent. 534 The Internet Assigned Numbers Authority (IANA) maintains a registry 535 of address-type and mta-name-type values, along with descriptions of 536 the meanings of each, or a reference to one or more specifications 537 that provide such descriptions. (The "rfc822" address-type is 538 defined in RFC-DSN-SMTP [7].) Registration forms for address-type 539 and mta-name-type appear in RFC-DSN-FORMAT [8]. 541 3.2. Message/disposition-notification Fields 543 3.2.1. The Reporting-UA field 545 reporting-ua-field = "Reporting-UA" ":" OWS ua-name OWS [ ";" OWS ua-product OWS ] 546 ua-name = *text-no-semi 547 ua-product = *([FWS] text) 548 text-no-semi = %d1-9 / ; "text" characters excluding NUL, CR, 549 %d11 / %d12 / %d14-58 / %d60-127 ; LF, or semi-colon 550 OWS = *WSP ; generators 551 / [CFWS] ; parsers 552 ; Optional whitespace. 553 ; MDN generators SHOULD use "*WSP" 554 ; (typically a single space or nothing. 555 ; It SHOULD be nothing at the end of a field), 556 ; unless an RFC 5322 "comment" is required. 557 ; 558 ; MDN parsers MUST parse it as "[CFWS]". 560 The Reporting-UA field is defined as follows: 562 An MDN describes the disposition of a message after it has been 563 delivered to a recipient. In all cases, the Reporting-UA is the MUA 564 that performed the disposition described in the MDN. This field is 565 optional, but recommended. For Internet Mail user agents, it is 566 recommended that this field contain both: the DNS name of the 567 particular instance of the MUA that generated the MDN, and the name 568 of the product. For example, 570 Reporting-UA: pc.example.com; Foomail 97.1 572 If the reporting MUA consists of more than one component (e.g., a 573 base program and plug-ins), this may be indicated by including a list 574 of product names. 576 3.2.2. The MDN-Gateway field 578 The MDN-Gateway field indicates the name of the gateway or MTA that 579 translated a foreign (non-Internet) message disposition notification 580 into this MDN. This field MUST appear in any MDN that was translated 581 by a gateway from a foreign system into MDN format, and MUST NOT 582 appear otherwise. 584 mdn-gateway-field = "MDN-Gateway" ":" OWS mta-name-type OWS ";" OWS mta-name OWS 585 mta-name = *text 587 For gateways into Internet Mail, the MTA-name-type will normally be 588 "smtp", and the mta-name will be the Internet domain name of the 589 gateway. 591 3.2.3. Original-Recipient field 593 The Original-Recipient field indicates the original recipient address 594 as specified by the sender of the message for which the MDN is being 595 issued. For Internet Mail messages, the value of the Original- 596 Recipient field is obtained from the Original-Recipient header field 597 from the message for which the MDN is being generated. If there is 598 no Original-Recipient header field in the message, then the Original- 599 Recipient field MUST be omitted, unless the same information is 600 reliably available some other way. If there is an Original-Recipient 601 header field in the original message (or original recipient 602 information is reliably available some other way), then the Original- 603 Recipient field must be supplied. If there is more than one 604 Original-Recipient header field in the message, the MUA may choose 605 the one to use, or act as if no Original-Recipient header field is 606 present. 608 original-recipient-field = 609 "Original-Recipient" ":" OWS address-type OWS ";" OWS generic-address OWS 610 generic-address = *text 612 The address-type field indicates the type of the original recipient 613 address. If the message originated within the Internet, the address- 614 type field will normally be "rfc822", and the address will be 615 according to the syntax specified in RFC-MSGFMT [2]. The value 616 "unknown" should be used if the Reporting MUA cannot determine the 617 type of the original recipient address from the message envelope. 618 This address is the same as that provided by the sender and can be 619 used to automatically correlate MDN reports with original messages on 620 a per recipient basis. 622 3.2.4. Final-Recipient field 624 The Final-Recipient field indicates the recipient for which the MDN 625 is being issued. This field MUST be present. 627 The syntax of the field is as follows: 629 final-recipient-field = 630 "Final-Recipient" ":" OWS address-type OWS ";" OWS generic-address OWS 632 The generic-address subfield of the Final-Recipient field MUST 633 contain the mailbox address of the recipient (from the From header 634 field of the MDN) as it was when the MDN was generated by the MUA. 636 The Final-Recipient address may differ from the address originally 637 provided by the sender, because it may have been transformed during 638 forwarding and gatewaying into a totally unrecognizable mess. 639 However, in the absence of the optional Original-Recipient field, the 640 Final-Recipient field and any returned content may be the only 641 information available with which to correlate the MDN with a 642 particular message recipient. 644 The address-type subfield indicates the type of address expected by 645 the reporting MTA in that context. Recipient addresses obtained via 646 SMTP will normally be of address-type "rfc822". 648 Since mailbox addresses (including those used in the Internet) may be 649 case sensitive, the case of alphabetic characters in the address MUST 650 be preserved. 652 3.2.5. Original-Message-ID field 654 The Original-Message-ID field indicates the message-ID of the message 655 for which the MDN is being issued. It is obtained from the Message- 656 ID header field of the message for which the MDN is issued. This 657 field MUST be present if the original message contained a Message-ID 658 header field. The syntax of the field is as follows: 660 original-message-id-field = 661 "Original-Message-ID" ":" msg-id 663 The msg-id token is as specified in RFC-MSGFMT [2]. 665 3.2.6. Disposition field 667 The Disposition field indicates the action performed by the 668 Reporting-MUA on behalf of the user. This field MUST be present. 670 The syntax for the Disposition field is: 672 disposition-field = 673 "Disposition" ":" OWS disposition-mode OWS ";" 674 OWS disposition-type 675 [ OWS "/" OWS disposition-modifier 676 *( OWS "," OWS disposition-modifier ) ] OWS 677 disposition-mode = action-mode OWS "/" OWS sending-mode 678 action-mode = "manual-action" / "automatic-action" 679 sending-mode = "MDN-sent-manually" / "MDN-sent-automatically" 680 disposition-type = "displayed" / "deleted" / "dispatched" / 681 "processed" 682 disposition-modifier = "error" / disposition-modifier-extension 683 disposition-modifier-extension = atom 685 The disposition-mode, disposition-type, and disposition-modifier may 686 be spelled in any combination of upper and lower case characters. 688 3.2.6.1. Disposition modes 690 The following disposition modes are defined: 692 "manual-action" The disposition described by the disposition type 693 was a result of an explicit instruction by the 694 user rather than some sort of automatically 695 performed action. 697 "automatic-action" The disposition described by the disposition type 698 was a result of an automatic action, rather than 699 an explicit instruction by the user for this 700 message. 702 "Manual-action" and "automatic-action" are mutually exclusive. One 703 or the other MUST be specified. 705 "MDN-sent-manually" The user explicitly gave permission for this 706 particular MDN to be sent. 708 "MDN-sent-automatically" The MDN was sent because the MUA had 709 previously been configured to do so 710 automatically. 712 "MDN-sent-manually" and "MDN-sent-automatically" are mutually 713 exclusive. One or the other MUST be specified. 715 3.2.6.2. Disposition types 717 The following disposition-types are defined: 719 "displayed" The message has been displayed by the MUA to 720 someone reading the recipient's mailbox. There 721 is no guarantee that the content has been read or 722 understood. 724 "dispatched" The message has been sent somewhere in some 725 manner (e.g., printed, faxed, forwarded) without 726 necessarily having been previously displayed to 727 the user. The user may or may not see the 728 message later. 730 "processed" The message has been processed in some manner 731 (i.e., by some sort of rules or server) without 732 being displayed to the user. The user may or may 733 not see the message later, or there may not even 734 be a human user associated with the mailbox. 736 "deleted" The message has been deleted. The recipient may 737 or may not have seen the message. The recipient 738 might "undelete" the message at a later time and 739 read the message. 741 3.2.6.3. Disposition modifiers 743 Only the extension disposition modifiers is defined: 745 disposition-modifier-extension 746 Disposition modifiers may be defined in the 747 future by later revisions or extensions to this 748 specification. Disposition value names beginning 749 with "X-" will never be defined as standard 750 values; such names are reserved for experimental 751 use. MDN disposition value names NOT beginning 752 with "X-" MUST be registered with the Internet 753 Assigned Numbers Authority (IANA) and described 754 in a standards-track RFC or an experimental RFC 755 approved by the IESG. (See Section 10 for a 756 registration form.) MDNs with disposition 757 modifier names not understood by the receiving 758 MUA MAY be silently ignored or placed in the 759 user's mailbox without special interpretation. 760 They MUST not cause any error message to be sent 761 to the sender of the MDN. 763 If an MUA developer does not wish to register the meanings of such 764 disposition modifier extensions, "X-" modifiers may be used for this 765 purpose. To avoid name collisions, the name of the MUA 766 implementation should follow the "X-", (e.g., "X-Foomail-"). 768 It is not required that an MUA be able to generate all of the 769 possible values of the Disposition field. 771 A user agent MUST NOT issue more than one MDN on behalf of each 772 particular recipient. That is, once an MDN has been issued on behalf 773 of a recipient, no further MDNs may be issued on behalf of that 774 recipient, even if another disposition is performed on the message. 775 However, if a message is forwarded, a "dispatched" MDN MAY be issued 776 for the recipient doing the forwarding and the recipient of the 777 forwarded message may also cause an MDN to be generated. 779 3.2.7. Failure and Error Fields 781 The Failure and Error fields are used to supply additional 782 information in the form of text messages when the "failure" 783 disposition type or "error" disposition modifier appear. The syntax 784 is as follows: 786 failure-field = "Failure" ":" *([FWS] text) 787 error-field = "Error" ":" *([FWS] text) 789 3.3. Extension-fields 791 Additional MDN fields may be defined in the future by later revisions 792 or extensions to this specification. Extension-field names beginning 793 with "X-" will never be defined as standard fields; such names are 794 reserved for experimental use. MDN field names NOT beginning with 795 "X-" MUST be registered with the Internet Assigned Numbers Authority 796 (IANA) and described in a standards-track RFC or an experimental RFC 797 approved by the IESG. (See Section 10 for a registration form.) MDN 798 Extension-fields may be defined for the following reasons: 800 a. To allow additional information from foreign disposition reports 801 to be tunneled through Internet MDNs. The names of such MDN 802 fields should begin with an indication of the foreign environment 803 name (e.g., X400-Physical-Forwarding-Address). 805 b. To allow transmission of diagnostic information that is specific 806 to a particular mail user agent (MUA). The names of such MDN 807 fields should begin with an indication of the MUA implementation 808 that produced the MDN (e.g., Foomail-information). 810 If an application developer does not wish to register the meanings of 811 such extension fields, "X-" fields may be used for this purpose. To 812 avoid name collisions, the name of the application implementation 813 should follow the "X-", (e.g., "X-Foomail-Log-ID" or "X-Foomail-EDI- 814 info"). 816 4. Timeline of events 818 The following timeline shows when various events in the processing of 819 a message and generation of MDNs take place: 821 -- User composes message 823 -- User tells MUA to send message 825 -- MUA passes message to MTA (original recipient information passed 826 along) 828 -- MTA sends message to next MTA 830 -- Final MTA receives message 832 -- Final MTA delivers message to MUA (possibly generating a DSN) 834 -- MUA performs automatic processing and generates corresponding MDNs 835 ("dispatched", "processed" or "deleted" disposition type with 836 "automatic-action" and "MDN-sent-automatically" disposition modes) 838 -- MUA displays list of messages to user 840 -- User selects a message and requests that some action be performed 841 on it. 843 -- MUA performs requested action and, with user's permission, sends 844 an appropriate MDN ("displayed", "dispatched", "processed", or 845 "deleted" disposition type, with "manual-action" and "MDN-sent- 846 manually" or "MDN-sent-automatically" disposition mode). 848 -- User possibly performs other actions on message, but no further 849 MDNs are generated. 851 5. Conformance and Usage Requirements 853 An MUA or gateway conforms to this specification if it generates MDNs 854 according to the protocol defined in this memo. It is not necessary 855 to be able to generate all of the possible values of the Disposition 856 field. 858 MUAs and gateways MUST NOT generate the Original-Recipient field of 859 an MDN unless the mail protocols provide the address originally 860 specified by the sender at the time of submission. Ordinary SMTP 861 does not make that guarantee, but the SMTP extension defined in RFC- 862 DSN-SMTP [7] permits such information to be carried in the envelope 863 if it is available. The Original-Recipient header field defined in 864 this document provides a way for the MTA to pass the original 865 recipient address to the MUA. 867 Each sender-specified recipient address may result in more than one 868 MDN. If an MDN is requested for a recipient that is forwarded to 869 multiple recipients of an "alias" (as defined in RFC-DSN-SMTP [7], 870 section 6.2.7.3), each of the recipients may issue an MDN. 872 Successful distribution of a message to a mailing list exploder 873 SHOULD be considered the final disposition of the message. A mailing 874 list exploder MAY issue an MDN with a disposition type of "processed" 875 and disposition modes of "automatic-action" and "MDN-sent- 876 automatically" indicating that the message has been forwarded to the 877 list. In this case, the request for MDNs is not propagated to the 878 members of the list. 880 Alternatively, the mailing list exploder MAY issue no MDN and 881 propagate the request for MDNs to all members of the list. The 882 latter behavior is not recommended for any but small, closely knit 883 lists, as it might cause large numbers of MDNs to be generated and 884 may cause confidential subscribers to the list to be revealed. The 885 mailing list exploder MAY also direct MDNs to itself, correlate them, 886 and produce a report to the original sender of the message. 888 This specification places no restrictions on the processing of MDNs 889 received by user agents or mailing lists. 891 6. Security Considerations 893 The following security considerations apply when using MDNs: 895 6.1. Forgery 897 MDNs may be forged as easily as ordinary Internet electronic mail. 898 User agents and automatic mail handling facilities (such as mail 899 distribution list exploders) that wish to make automatic use of MDNs 900 should take appropriate precautions to minimize the potential damage 901 from denial-of-service attacks. 903 Security threats related to forged MDNs include the sending of: 905 a. A falsified disposition notification when the indicated 906 disposition of the message has not actually occurred, 908 b. Unsolicited MDNs 910 6.2. Privacy 912 Another dimension of security is privacy. There may be cases in 913 which a message recipient does not wish the disposition of messages 914 addressed to him to be known, or is concerned that the sending of 915 MDNs may reveal other sensitive information (e.g., when the message 916 was read). In this situation, it is acceptable for the MUA to 917 silently ignore requests for MDNs. 919 If the Disposition-Notification-To header field is passed on 920 unmodified when a message is distributed to the subscribers of a 921 mailing list, the subscribers to the list may be revealed to the 922 sender of the original message by the generation of MDNs. 924 Headers of the original message returned in part 3 of the multipart/ 925 report could reveal confidential information about host names and/or 926 network topology inside a firewall. 928 An unencrypted MDN could reveal confidential information about an 929 encrypted message, especially if all or part of the original message 930 is returned in part 3 of the multipart/report. Encrypted MDNs are 931 not defined in this specification. 933 In general, any optional MDN field may be omitted if the Reporting 934 MUA site or user determines that inclusion of the field would impose 935 too great a compromise of site confidentiality. The need for such 936 confidentiality must be balanced against the utility of the omitted 937 information in MDNs. 939 In some cases, someone with access to the message stream may use the 940 MDN request mechanism to monitor the mail reading habits of a target. 941 If the target is known to generate MDN reports, they could add a 942 disposition-notification-to field containing the envelope from 943 address along with a source route. The source route is ignored in 944 the comparison so the addresses will always match. But if the source 945 route is honored when the notification is sent, it could direct the 946 message to some other destination. This risk can be minimized by not 947 sending MDN's automatically. 949 6.3. Non-Repudiation 951 MDNs do not provide non-repudiation with proof of delivery. Within 952 the framework of today's Internet Mail, the MDNs defined in this 953 document provide valuable information to the mail user; however, MDNs 954 cannot be relied upon as a guarantee that a message was or was not 955 seen by the recipient. Even if MDNs are not actively forged, they 956 may be lost in transit. The recipient may bypass the MDN issuing 957 mechanism in some manner. 959 One possible solution for this purpose can be found in RFC-SEC- 960 SERVICES [11]. 962 6.4. Mail Bombing 964 The MDN request mechanism introduces an additional way of mailbombing 965 a mailbox. The MDN request notification provides an address to which 966 MDN's should be sent. It is possible for an attacking agent to send 967 a potentially large set of messages to otherwise unsuspecting third 968 party recipients with a false "disposition-notification-to:" address. 969 Automatic, or simplistic processing of such requests would result in 970 a flood of MDN notifications to the target of the attack. Such an 971 attack could overrun the capacity of the targeted mailbox and deny 972 service. 974 For that reason, MDN's SHOULD NOT be sent automatically where the 975 "disposition-notification-to:" address is different from the envelope 976 MAIL FROM address. See Section 2.1 for further discussion. 978 7. Collected ABNF Grammar 980 NOTE: The following lexical tokens are defined in RFC-MSGFMT [2]: 981 CRLF, FWS, CFWS, field-name, mailbox-list, msg-id, text, comment, 982 word. The following lexical tokens are defined in RFC-SMTP [1]: 983 atom. (Note that RFC-MSGFMT [2] also defines "atom", but the version 984 from RFC-SMTP [1] is more restrictive and this more restrictive 985 version is used in this document.) "encoded-word" construct defined 986 in RFC-MIME-HEADER [5] is allowed everywhere where RFC-MSGFMT [2] 987 "comment" is used, for example in CFWS. 989 Message header fields: 990 mdn-request-header = 991 "Disposition-Notification-To" ":" mailbox-list CRLF 992 Disposition-Notification-Options = 993 "Disposition-Notification-Options" ":" [FWS] 994 disposition-notification-parameter-list CRLF 995 disposition-notification-parameter-list = 996 disposition-notification-parameter 997 *([FWS] ";" [FWS] disposition-notification-parameter) 998 disposition-notification-parameter = attribute [FWS] "=" [FWS] 999 importance [FWS] "," [FWS] value *([FWS] "," [FWS] value) 1000 importance = "required" / "optional" 1001 attribute = atom 1002 value = word 1003 original-recipient-header = 1004 "Original-Recipient" ":" [FWS] address-type [FWS] ";" [FWS] generic-address 1006 Report content: 1007 disposition-notification-content = 1008 [ reporting-ua-field CRLF ] 1009 [ mdn-gateway-field CRLF ] 1011 [ original-recipient-field CRLF ] 1012 final-recipient-field CRLF 1013 [ original-message-id-field CRLF ] 1014 disposition-field CRLF 1015 *( failure-field CRLF ) 1016 *( error-field CRLF ) 1017 *( extension-field CRLF ) 1018 OWS = *WSP ; generators 1019 / [CFWS] ; parsers 1020 ; Optional whitespace. 1021 ; MDN generators SHOULD use "*WSP" 1022 ; (typically a single space or nothing. 1023 ; It SHOULD be nothing at the end of a field), 1024 ; unless an RFC 5322 "comment" is required. 1025 ; 1026 ; MDN parsers MUST parse it as "[CFWS]". 1027 address-type = atom 1028 mta-name-type = atom 1029 reporting-ua-field = "Reporting-UA" ":" OWS ua-name OWS [ ";" OWS ua-product OWS ] 1030 ua-name = *text-no-semi 1031 ua-product = *([FWS] text) 1032 text-no-semi = %d1-9 / ; "text" characters excluding NUL, CR, 1033 %d11 / %d12 / %d14-58 / %d60-127 ; LF, or semi-colon 1034 mdn-gateway-field = "MDN-Gateway" ":" OWS mta-name-type OWS ";" OWS mta-name 1035 mta-name = *text 1036 original-recipient-field = 1037 "Original-Recipient" ":" OWS address-type OWS ";" OWS generic-address OWS 1038 generic-address = *text 1039 final-recipient-field = 1040 "Final-Recipient" ":" OWS address-type OWS ";" OWS generic-address OWS 1041 original-message-id-field = "Original-Message-ID" ":" msg-id 1042 disposition-field = 1043 "Disposition" ":" OWS disposition-mode OWS ";" 1044 OWS disposition-type 1045 [ OWS "/" OWS disposition-modifier 1046 *( OWS "," OWS disposition-modifier ) ] OWS 1047 disposition-mode = action-mode OWS "/" OWS sending-mode 1048 action-mode = "manual-action" / "automatic-action" 1049 sending-mode = "MDN-sent-manually" / "MDN-sent-automatically" 1050 disposition-type = "displayed" / "deleted" / "dispatched" / 1051 "processed" 1052 disposition-modifier = "error" / disposition-modifier-extension 1053 disposition-modifier-extension = atom 1054 failure-field = "Failure" ":" *([FWS] text) 1055 error-field = "Error" ":" *([FWS] text) 1056 extension-field = extension-field-name ":" *([FWS] text) 1057 extension-field-name = field-name 1059 8. Guidelines for Gatewaying MDNs 1061 NOTE: This section provides non-binding recommendations for the 1062 construction of mail gateways that wish to provide semi-transparent 1063 disposition notifications between the Internet and another electronic 1064 mail system. Specific MDN gateway requirements for a particular pair 1065 of mail systems may be defined by other documents. 1067 8.1. Gatewaying from other mail systems to MDNs 1069 A mail gateway may issue an MDN to convey the contents of a "foreign" 1070 disposition notification over Internet Mail. When there are 1071 appropriate mappings from the foreign notification elements to MDN 1072 fields, the information may be transmitted in those MDN fields. 1073 Additional information (such as might be needed to tunnel the foreign 1074 notification through the Internet) may be defined in extension MDN 1075 fields. (Such fields should be given names that identify the foreign 1076 mail protocol, e.g., X400-* for X.400 protocol elements). 1078 The gateway must attempt to supply reasonable values for the 1079 Reporting-UA, Final-Recipient, and Disposition fields. These will 1080 normally be obtained by translating the values from the foreign 1081 notification into their Internet-style equivalents. However, some 1082 loss of information is to be expected. 1084 The sender-specified recipient address and the original message-id, 1085 if present in the foreign notification, should be preserved in the 1086 Original-Recipient and Original-Message-ID fields. 1088 The gateway should also attempt to preserve the "final" recipient 1089 address from the foreign system. Whenever possible, foreign protocol 1090 elements should be encoded as meaningful printable ASCII strings. 1092 For MDNs produced from foreign disposition notifications, the name of 1093 the gateway MUST appear in the MDN-Gateway field of the MDN. 1095 8.2. Gatewaying from MDNs to other mail systems 1097 It may be possible to gateway MDNs from the Internet into a foreign 1098 mail system. The primary purpose of such gatewaying is to convey 1099 disposition information in a form that is usable by the destination 1100 system. A secondary purpose is to allow "tunneling" of MDNs through 1101 foreign mail systems in case the MDN may be gatewayed back into the 1102 Internet. 1104 In general, the recipient of the MDN (i.e., the sender of the 1105 original message) will want to know, for each recipient: the closest 1106 available approximation to the original recipient address, and the 1107 disposition (displayed, printed, etc.). 1109 If possible, the gateway should attempt to preserve the Original- 1110 Recipient address and Original-Message-ID (if present) in the 1111 resulting foreign disposition report. 1113 If it is possible to tunnel an MDN through the destination 1114 environment, the gateway specification may define a means of 1115 preserving the MDN information in the disposition reports used by 1116 that environment. 1118 8.3. Gatewaying of MDN-requests to other mail systems 1120 By use of the separate disposition-notification-to request header 1121 field, this specification offers a richer functionality than most, if 1122 not all, other email systems. In most other email systems, the 1123 notification recipient is identical to the message sender as 1124 indicated in the "from" address. There are two interesting cases 1125 when gatewaying into such systems: 1127 1. If the address in the disposition-notification-to header field is 1128 identical to the address in the SMTP "MAIL FROM", the expected 1129 behavior will result, even if the disposition-notification-to 1130 information is lost. Systems should propagate the MDN request. 1132 2. If the address in the disposition-notification-to header field is 1133 different from the address in the SMTP "MAIL FROM", gatewaying 1134 into a foreign system without a separate notification address 1135 will result in unintended behavior. This is especially important 1136 when the message arrives via a mailing list expansion software 1137 that may specifically replace the SMTP "MAIL FROM" address with 1138 an alternate address. In such cases, the MDN request should not 1139 be gatewayed and should be silently dropped. This is consistent 1140 with other forms of non-support for MDN. 1142 9. Example 1144 NOTE: This example is provided as illustration only, and is not 1145 considered part of the MDN protocol specification. If the example 1146 conflicts with the protocol definition above, the example is wrong. 1148 Likewise, the use of *-type subfield names or extension fields in 1149 this example is not to be construed as a definition for those type 1150 names or extension fields. 1152 This is an MDN issued after a message has been displayed to the user 1153 of an Internet Mail user agent. 1155 Date: Wed, 20 Sep 1995 00:19:00 (EDT) -0400 1156 From: Joe Recipient 1157 Message-Id: <199509200019.12345@example.com> 1158 Subject: Disposition notification 1159 To: Jane Sender 1160 MIME-Version: 1.0 1161 Content-Type: multipart/report; report-type=disposition-notification; 1162 boundary="RAA14128.773615765/example.com" 1164 --RAA14128.773615765/example.com 1166 The message sent on 1995 Sep 19 at 13:30:00 (EDT) -0400 to Joe 1167 Recipient with subject "First draft of 1168 report" has been displayed. 1169 This is no guarantee that the message has been read or understood. 1171 --RAA14128.773615765/example.com 1172 content-type: message/disposition-notification 1174 Reporting-UA: joes-pc.cs.example.com; Foomail 97.1 1175 Original-Recipient: rfc822;Joe_Recipient@example.com 1176 Final-Recipient: rfc822;Joe_Recipient@example.com 1177 Original-Message-ID: <199509192301.23456@example.org> 1178 Disposition: manual-action/MDN-sent-manually; displayed 1180 --RAA14128.773615765/example.com 1181 content-type: message/rfc822 1183 [original message optionally goes here] 1185 --RAA14128.773615765/example.com-- 1187 10. IANA Considerations 1189 This document specifies three types of parameters that must be 1190 registered with the Internet Assigned Numbers Authority (IANA). 1192 The forms below are for use when registering a new disposition- 1193 notification-parameter name for the Disposition-Notification-Options 1194 header field, a new disposition modifier name, or a new MDN extension 1195 field. Each piece of information required by a registration form may 1196 be satisfied either by providing the information on the form itself, 1197 or by including a reference to a published, publicly available 1198 specification that includes the necessary information. IANA MAY 1199 reject registrations because of incomplete registration forms or 1200 incomplete specifications. 1202 To register, complete the following applicable form and send it via 1203 electronic mail to . 1205 10.1. Disposition-Notification-Options header field disposition- 1206 notification-parameter names 1208 A registration for a Disposition-Notification-Options header field 1209 disposition-notification-parameter name MUST include the following 1210 information: 1212 a. The proposed disposition-notification-parameter name. 1214 b. The syntax for disposition-notification-parameter values, 1215 specified using BNF, ABNF, regular expressions, or other non- 1216 ambiguous language. 1218 c. If disposition-notification-parameter values are not composed 1219 entirely of graphic characters from the US-ASCII repertoire, a 1220 specification for how they are to be encoded as graphic US-ASCII 1221 characters in a Disposition-Notification-Options header field. 1223 d. A reference to a standards track RFC or experimental RFC approved 1224 by the IESG that describes the semantics of the disposition- 1225 notification-parameter values. 1227 10.2. Disposition modifier names 1229 A registration for a disposition-modifier name (used in the 1230 Disposition field of a message/disposition-notification) MUST include 1231 the following information: 1233 a. The proposed disposition-modifier name. 1235 b. A reference to a standards track RFC or experimental RFC approved 1236 by the IESG that describes the semantics of the disposition 1237 modifier. 1239 10.3. MDN extension field names 1241 A registration for an MDN extension-field name MUST include the 1242 following information: 1244 a. The proposed extension field name. 1246 b. The syntax for extension values, specified using BNF, ABNF, 1247 regular expressions, or other non-ambiguous language. 1249 c. If extension-field values are not composed entirely of graphic 1250 characters from the US-ASCII repertoire, a specification for how 1251 they are to be encoded as graphic US-ASCII characters in a 1252 Disposition-Notification-Options header field. 1254 d. A reference to a standards track RFC or experimental RFC approved 1255 by the IESG that describes the semantics of the extension field. 1257 11. Acknowledgements 1259 The contributions of Bruce Lilly, Alfred Hoenes and Pete Resnick are 1260 gratefully acknowledged for this revision. 1262 The contributions of Roger Fajman and Greg Vaudreuil to earlier 1263 versions of this document are also gratefully acknowledged. 1265 12. References 1267 12.1. Normative References 1269 [1] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, 1270 DOI 10.17487/RFC5321, October 2008, 1271 . 1273 [2] Resnick, P., Ed., "Internet Message Format", RFC 5322, 1274 DOI 10.17487/RFC5322, October 2008, 1275 . 1277 [3] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1278 Extensions (MIME) Part One: Format of Internet Message 1279 Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996, 1280 . 1282 [4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1283 Extensions (MIME) Part Two: Media Types", RFC 2046, 1284 DOI 10.17487/RFC2046, November 1996, 1285 . 1287 [5] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 1288 Part Three: Message Header Extensions for Non-ASCII Text", 1289 RFC 2047, DOI 10.17487/RFC2047, November 1996, 1290 . 1292 [6] Vaudreuil, G., "The Multipart/Report Content Type for the 1293 Reporting of Mail System Administrative Messages", 1294 RFC 3462, DOI 10.17487/RFC3462, January 2003, 1295 . 1297 [7] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service 1298 Extension for Delivery Status Notifications (DSNs)", 1299 RFC 3461, DOI 10.17487/RFC3461, January 2003, 1300 . 1302 [8] Moore, K. and G. Vaudreuil, "An Extensible Message Format 1303 for Delivery Status Notifications", RFC 3464, 1304 DOI 10.17487/RFC3464, January 2003, 1305 . 1307 [9] Bradner, S., "Key words for use in RFCs to Indicate 1308 Requirement Levels", BCP 14, RFC 2119, 1309 DOI 10.17487/RFC2119, March 1997, 1310 . 1312 [10] Melnikov, A., "Message Disposition Notification (MDN) 1313 profile for Internet Message Access Protocol (IMAP)", 1314 RFC 3503, DOI 10.17487/RFC3503, March 2003, 1315 . 1317 12.2. Informative References 1319 [11] Hoffman, P., Ed., "Enhanced Security Services for S/MIME", 1320 RFC 2634, DOI 10.17487/RFC2634, June 1999, 1321 . 1323 [12] Murchison, K., "Sieve Email Filtering: Subaddress 1324 Extension", RFC 5233, DOI 10.17487/RFC5233, January 2008, 1325 . 1327 [13] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 1328 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 1329 . 1331 Appendix A. Changes from RFC 3798 1333 The values of "dispatched" and "processed" were lost from the ABNF 1334 for "disposition-type". 1336 Because the warning disposition modifier was previously removed, 1337 warning-field has also been removed. 1339 The ABNF for ua-name and ua-product included semi-colon, which could 1340 not be distinguished from *text in the production. The ua-name was 1341 restricted to not include semi-colon. Semi-colon can still appear in 1342 the ua-product. 1344 The ABNF did not indicate all places that whitespace was allowable, 1345 in particular folding whitespace, although all implementations allow 1346 whitespace and folding in the header fields just like any other 1347 RFC5322 [2]-formatted header field. There were also a number of 1348 places in the ABNF that inconsistently permitted comments and 1349 whitespace in one leg of the production and not another. The ABNF 1350 now specifies FWS and CFWS in several places that should have already 1351 been specified by the grammar. 1353 Extension-field was defined in the collected grammar but not in the 1354 main text. 1356 The comparison of mailboxes in Disposition-Notification-To to the 1357 Return-Path addr-spec was clarified. 1359 The use of the grammar production "parameter" was confusing with the 1360 RFC2045 [3] production of the same name, as well as other uses of the 1361 same term. These have been clarified. 1362 [[CREF1: Not sure what to do with this one: (From Bruce) In the case 1363 of the message header fields, RFC 2822 also specifies minimum and 1364 maximum counts for each header field, and similar guidance would 1365 clarify 3798 (e.g. are multiple Disposition-Notification-Options 1366 fields permitted in a single message header, and if so, what 1367 semantics apply?). ]] 1369 A clarification was added on the extent of the 7bit nature of MDNs. 1371 Uses of the terms "may" and "might" were clarified. 1373 A clarification was added on the order of the fields in the message/ 1374 disposition-notification content. 1375 [[CREF2: Not sure what to do with this one: (From Bruce) 3.1.1 1376 explicitly mentions use of RFC 2047 encoded-words in comments 1377 (however, as noted above there is no explicit provision for 1378 comments), but fails to mention the other contexts in which encoded- 1379 words may be used, viz. in an RFC [2]822 "phrase" (e.g. in the 1380 display name of a name-addr mailbox in Disposition-Notification-To 1381 (therefore, the discussion of encoded-words should probably be moved 1382 earlier in the document, prior to the specification of Disposition- 1383 Notification-To]), and in unstructured text (i.e. every instance of 1384 *text in the ABNF). In particular, use of encoded-words might be 1385 highly desirable in the following places: *) the ua-product portion 1386 of the Reporting-UA field; *) the generic-address part of the 1387 Original-Recipient and Final-Recipient fields; *) the (unstructured) 1388 field bodies of Error, Failure, and Warning fields; in structured 1389 extension fields where the context (per RFC 2047) is appropriate in 1390 unstructured extension fields; *) in X- extension fields (see RFC 1391 2047 for related X- message header fields). In cases where the field 1392 syntax is shared with DSN fields, some coordination with the RFC 346x 1393 authors might be desirable. ]] 1395 Authors' Addresses 1397 Tony Hansen (editor) 1398 AT&T Laboratories 1399 200 Laurel Ave. South 1400 Middletown, NJ 07748 1401 USA 1403 Email: tony+rfc3798@maillennium.att.com 1405 Alexey Melnikov (editor) 1406 Isode Ltd 1407 14 Castle Mews 1408 Hampton, Middlesex TW12 2NP 1409 UK 1411 Email: Alexey.Melnikov@isode.com