7 Network Working Group K. Moore
8 Request for Comments: 1894 University of Tennessee
9 Category: Standards Track G. Vaudreuil
10 Octel Network Services
14 An Extensible Message Format for Delivery Status Notifications
18 This document specifies an Internet standards track protocol for the
19 Internet community, and requests discussion and suggestions for
20 improvements. Please refer to the current edition of the "Internet
21 Official Protocol Standards" (STD 1) for the standardization state
22 and status of this protocol. Distribution of this memo is unlimited.
26 This memo defines a MIME content-type that may be used by a message
27 transfer agent (MTA) or electronic mail gateway to report the result
28 of an attempt to deliver a message to one or more recipients. This
29 content-type is intended as a machine-processable replacement for the
30 various types of delivery status notifications currently used in
31 Internet electronic mail.
33 Because many messages are sent between the Internet and other
34 messaging systems (such as X.400 or the so-called "LAN-based"
35 systems), the DSN protocol is designed to be useful in a multi-
36 protocol messaging environment. To this end, the protocol described
37 in this memo provides for the carriage of "foreign" addresses and
38 error codes, in addition to those normally used in Internet mail.
39 Additional attributes may also be defined to support "tunneling" of
40 foreign notifications through Internet mail.
42 Any questions, comments, and reports of defects or ambiguities in
43 this specification may be sent to the mailing list for the NOTARY
44 working group of the IETF, using the address
45 <notifications@cs.utk.edu>. Requests to subscribe to the mailing
46 list should be addressed to <notifications-request@cs.utk.edu>.
47 Implementors of this specification are encouraged to subscribe to the
48 mailing list, so that they will quickly be informed of any problems
49 which might hinder interoperability.
51 NOTE: This document is a Proposed Standard. If and when this
52 protocol is submitted for Draft Standard status, any normative text
53 (phrases containing SHOULD, SHOULD NOT, MUST, MUST NOT, or MAY) in
54 this document will be re-evaluated in light of implementation
58 Moore & Vaudreuil Standards Track [Page 1]
60 RFC 1894 Delivery Status Notifications January 1996
63 experience, and are thus subject to change.
67 This memo defines a MIME [1] content-type for delivery status
68 notifications (DSNs). A DSN can be used to notify the sender of a
69 message of any of several conditions: failed delivery, delayed
70 delivery, successful delivery, or the gatewaying of a message into an
71 environment that may not support DSNs. The "message/delivery-status"
72 content-type defined herein is intended for use within the framework
73 of the "multipart/report" content type defined in [2].
75 This memo defines only the format of the notifications. An extension
76 to the Simple Message Transfer Protocol (SMTP) [3] to fully support
77 such notifications is the subject of a separate memo [4].
81 The DSNs defined in this memo are expected to serve several purposes:
83 (a) Inform human beings of the status of message delivery processing, as
84 well as the reasons for any delivery problems or outright failures,
85 in a manner which is largely independent of human language;
87 (b) Allow mail user agents to keep track of the delivery status of
88 messages sent, by associating returned DSNs with earlier message
91 (c) Allow mailing list exploders to automatically maintain their
92 subscriber lists when delivery attempts repeatedly fail;
94 (d) Convey delivery and non-delivery notifications resulting from
95 attempts to deliver messages to "foreign" mail systems via a
98 (e) Allow "foreign" notifications to be tunneled through a MIME-capable
99 message system and back into the original messaging system that
100 issued the original notification, or even to a third messaging
103 (f) Allow language-independent, yet reasonably precise, indications of
104 the reason for the failure of a message to be delivered (once status
105 codes of sufficient precision are defined); and
107 (g) Provide sufficient information to remote MTA maintainers (via
108 "trouble tickets") so that they can understand the nature of
109 reported errors. This feature is used in the case that failure to
110 deliver a message is due to the malfunction of a remote MTA and the
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116 RFC 1894 Delivery Status Notifications January 1996
119 sender wants to report the problem to the remote MTA administrator.
123 These purposes place the following constraints on the notification
126 (a) It must be readable by humans as well as being machine-parsable.
128 (b) It must provide enough information to allow message senders (or the
129 user agents) to unambiguously associate a DSN with the message that
130 was sent and the original recipient address for which the DSN is
131 issued (if such information is available), even if the message was
132 forwarded to another recipient address.
134 (c) It must be able to preserve the reason for the success or failure of
135 a delivery attempt in a remote messaging system, using the
136 "language" (mailbox addresses and status codes) of that remote
139 (d) It must also be able to describe the reason for the success or
140 failure of a delivery attempt, independent of any particular human
141 language or of the "language" of any particular mail system.
143 (e) It must preserve enough information to allow the maintainer of a
144 remote MTA to understand (and if possible, reproduce) the conditions
145 that caused a delivery failure at that MTA.
147 (f) For any notifications issued by foreign mail systems, which are
148 translated by a mail gateway to the DSN format, the DSN must
149 preserve the "type" of the foreign addresses and error codes, so
150 that these may be correctly interpreted by gateways.
152 A DSN contains a set of per-message fields which identify the message
153 and the transaction during which the message was submitted, along
154 with other fields that apply to all delivery attempts described by
155 the DSN. The DSN also includes a set of per-recipient fields to
156 convey the result of the attempt to deliver the message to each of
157 one or more recipients.
161 A message may be transmitted through several message transfer agents
162 (MTAs) on its way to a recipient. For a variety of reasons,
163 recipient addresses may be rewritten during this process, so each MTA
164 may potentially see a different recipient address. Depending on the
165 purpose for which a DSN is used, different formats of a particular
166 recipient address will be needed.
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172 RFC 1894 Delivery Status Notifications January 1996
175 Several DSN fields are defined in terms of the view from a particular
176 MTA in the transmission. The MTAs are assigned the following names:
180 The Original MTA is the one to which the message is submitted for
181 delivery by the sender of the message.
185 For any DSN, the Reporting MTA is the one which is reporting the
186 results of delivery attempts described in the DSN.
188 If the delivery attempts described occurred in a "foreign" (non-
189 Internet) mail system, and the DSN was produced by translating the
190 foreign notice into DSN format, the Reporting MTA will still identify
191 the "foreign" MTA where the delivery attempts occurred.
193 (c) Received-From MTA
195 The Received-From MTA is the MTA from which the Reporting MTA
196 received the message, and accepted responsibility for delivery of the
201 If an MTA determines that it must relay a message to one or more
202 recipients, but the message cannot be transferred to its "next hop"
203 MTA, or if the "next hop" MTA refuses to accept responsibility for
204 delivery of the message to one or more of its intended recipients,
205 the relaying MTA may need to issue a DSN on behalf of the recipients
206 for whom the message cannot be delivered. In this case the relaying
207 MTA is the Reporting MTA, and the "next hop" MTA is known as the
226 Moore & Vaudreuil Standards Track [Page 4]
228 RFC 1894 Delivery Status Notifications January 1996
231 Figure 1 illustrates the relationship between the various MTAs.
234 +-----+ +--------+ +---------+ +---------+ +------+
235 | | | | |Received-| | | | |
236 | | => |Original| => ... => | From | => |Reporting| ===> |Remote|
237 | user| | MTA | | MTA | | MTA | <No! | MTA |
238 |agent| +--------+ +---------+ +----v----+ +------+
240 | | <-------------------------------------------+
241 +-----+ (DSN returned to sender by Reporting MTA)
244 Figure 1. Original, Received-From, Reporting and Remote MTAs
247 Each of these MTAs may provide information which is useful in a DSN:
249 + Ideally, the DSN will contain the address of each recipient as
250 originally specified to the Original MTA by the sender of the message.
251 This version of the address is needed (rather than a forwarding
252 address or some modified version of the original address) so that the
253 sender may compare the recipient address in the DSN with the address
254 in the sender's records (e.g. an address book for an individual, the
255 list of subscribers for a mailing list) and take appropriate action.
257 Similarly, the DSN might contain an "envelope identifier" that was
258 known to both the sender's user agent and the Original MTA at the time
259 of message submission, and which, if included in the DSN, can be used
260 by the sender to keep track of which messages were or were not
263 + If a message was (a) forwarded to a different address than that
264 specified by the sender, (b) gatewayed to a different mail system than
265 that used by the sender, or (c) subjected to address rewriting during
266 transmission, the "final" form of the recipient address (i.e. the one
267 seen by the Reporting MTA) will be different than the original
268 (sender-specified) recipient address. Just as the sender's user agent
269 (or the sender) prefers the original recipient address, so the "final"
270 address is needed when reporting a problem to the postmaster of the
271 site where message delivery failed, because only the final recipient
272 address will allow her to reproduce the conditions that caused the
275 + A "failed" DSN should contain the most accurate explanation for the
276 delivery failure that is available. For ease of interpretation, this
277 information should be a format which is independent of the mail
278 transport system that issued the DSN. However, if a foreign error
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284 RFC 1894 Delivery Status Notifications January 1996
287 code is translated into some transport-independent format, some
288 information may be lost. It is therefore desirable to provide both a
289 transport-independent status code and a mechanism for reporting
290 transport-specific codes. Depending on the circumstances that
291 produced delivery failure, the transport-specific code might be
292 obtained from either the Reporting MTA or the Remote MTA.
294 Since different values for "recipient address" and "delivery status
295 code" are needed according to the circumstance in which a DSN will be
296 used, and since the MTA that issues the DSN cannot anticipate those
297 circumstances, the DSN format described here may contain both the
298 original and final forms of a recipient address, and both a
299 transport-independent and a transport-specific indication of delivery
302 Extension fields may also be added by the Reporting MTA as needed to
303 provide additional information for use in a trouble ticket or to
304 preserve information for tunneling of foreign delivery reports
305 through Internet DSNs.
307 The Original, Reporting, and Remote MTAs may exist in very different
308 environments and use dissimilar transport protocols, MTA names,
309 address formats, and delivery status codes. DSNs therefore do not
310 assume any particular format for mailbox addresses, MTA names, or
311 transport-specific status codes. Instead, the various DSN fields
312 that carry such quantities consist of a "type" subfield followed by a
313 subfield whose contents are ordinary text characters, and the format
314 of which is indicated by the "type" subfield. This allows a DSN to
315 convey these quantities regardless of format.
317 2. Format of a Delivery Status Notification
319 A DSN is a MIME message with a top-level content-type of
320 multipart/report (defined in [2]). When a multipart/report content
321 is used to transmit a DSN:
323 (a) The report-type parameter of the multipart/report content is
326 (b) The first component of the multipart/report contains a human-
327 readable explanation of the DSN, as described in [2].
329 (c) The second component of the multipart/report is of content-type
330 message/delivery-status, described in section 2.1 of this document.
332 (d) If the original message or a portion of the message is to be
333 returned to the sender, it appears as the third component of the
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340 RFC 1894 Delivery Status Notifications January 1996
343 NOTE: For delivery status notifications gatewayed from foreign
344 systems, the headers of the original message may not be available.
345 In this case the third component of the DSN may be omitted, or it
346 may contain "simulated" RFC 822 headers which contain equivalent
347 information. In particular, it is very desirable to preserve the
348 subject, date, and message-id (or equivalent) fields from the
351 The DSN MUST be addressed (in both the message header and the
352 transport envelope) to the return address from the transport envelope
353 which accompanied the original message for which the DSN was
354 generated. (For a message that arrived via SMTP, the envelope return
355 address appears in the MAIL FROM command.)
357 The From field of the message header of the DSN SHOULD contain the
358 address of a human who is responsible for maintaining the mail system
359 at the Reporting MTA site (e.g. Postmaster), so that a reply to the
360 DSN will reach that person. Exception: if a DSN is translated from a
361 foreign delivery report, and the gateway performing the translation
362 cannot determine the appropriate address, the From field of the DSN
363 MAY be the address of a human who is responsible for maintaining the
366 The envelope sender address of the DSN SHOULD be chosen to ensure
367 that no delivery status reports will be issued in response to the DSN
368 itself, and MUST be chosen so that DSNs will not generate mail loops.
369 Whenever an SMTP transaction is used to send a DSN, the MAIL FROM
370 command MUST use a NULL return address, i.e. "MAIL FROM:<>".
372 A particular DSN describes the delivery status for exactly one
373 message. However, an MTA MAY report on the delivery status for
374 several recipients of the same message in a single DSN. Due to the
375 nature of the mail transport system (where responsibility for
376 delivery of a message to its recipients may be split among several
377 MTAs, and delivery to any particular recipient may be delayed),
378 multiple DSNs may be still be issued in response to a single message
394 Moore & Vaudreuil Standards Track [Page 7]
396 RFC 1894 Delivery Status Notifications January 1996
399 2.1 The message/delivery-status content-type
401 The message/delivery-status content-type is defined as follows:
403 MIME type name: message
404 MIME subtype name: delivery-status
405 Optional parameters: none
406 Encoding considerations: "7bit" encoding is sufficient and
407 MUST be used to maintain readability
408 when viewed by non-MIME mail
410 Security considerations: discussed in section 4 of this memo.
412 The message/delivery-status report type for use in the
413 multipart/report is "delivery-status".
415 The body of a message/delivery-status consists of one or more
416 "fields" formatted according to the ABNF of RFC 822 header "fields"
417 (see [6]). The per-message fields appear first, followed by a blank
418 line. Following the per-message fields are one or more groups of
419 per-recipient fields. Each group of per-recipient fields is preceded
420 by a blank line. Using the ABNF of RFC 822, the syntax of the
421 message/delivery-status content is as follows:
423 delivery-status-content =
424 per-message-fields 1*( CRLF per-recipient-fields )
426 The per-message fields are described in section 2.2. The per-
427 recipient fields are described in section 2.3.
430 2.1.1 General conventions for DSN fields
432 Since these fields are defined according to the rules of RFC 822, the
433 same conventions for continuation lines and comments apply.
434 Notification fields may be continued onto multiple lines by beginning
435 each additional line with a SPACE or HTAB. Text which appears in
436 parentheses is considered a comment and not part of the contents of
437 that notification field. Field names are case-insensitive, so the
438 names of notification fields may be spelled in any combination of
439 upper and lower case letters. Comments in DSN fields may use the
440 "encoded-word" construct defined in [7].
442 A number of DSN fields are defined to have a portion of a field body
443 of "xtext". "xtext" is used to allow encoding sequences of octets
444 which contain values outside the range [1-127 decimal] of traditional
445 ASCII characters, and also to allow comments to be inserted in the
446 data. Any octet may be encoded as "+" followed by two upper case
450 Moore & Vaudreuil Standards Track [Page 8]
452 RFC 1894 Delivery Status Notifications January 1996
455 hexadecimal digits. (The "+" character MUST be encoded as "+2B".)
456 With certain exceptions, octets that correspond to ASCII characters
457 may be represented as themselves. SPACE and HTAB characters are
458 ignored. Comments may be included by enclosing them in parenthesis.
459 Except within comments, encoded-words such as defined in [7] may NOT
462 "xtext" is formally defined as follows:
464 xtext = *( xchar / hexchar / linear-white-space / comment )
466 xchar = any ASCII CHAR between "!" (33) and "~" (126) inclusive,
467 except for "+", "\" and "(".
469 "hexchar"s are intended to encode octets that cannot be represented
470 as plain text, either because they are reserved, or because they are
471 non-printable. However, any octet value may be represented by a
474 hexchar = ASCII "+" immediately followed by two upper case
477 When encoding an octet sequence as xtext:
479 + Any ASCII CHAR between "!" and "~" inclusive, except for "+", "\",
480 and "(", MAY be encoded as itself. (Some CHARs in this range may
481 also be encoded as "hexchar"s, at the implementor's discretion.)
483 + ASCII CHARs that fall outside the range above must be encoded as
486 + Line breaks (CR LF SPACE) MAY be inserted as necessary to keep line
487 lengths from becoming excessive.
489 + Comments MAY be added to clarify the meaning for human readers.
491 2.1.2 "*-type" subfields
493 Several DSN fields consist of a "-type" subfield, followed by a
494 semicolon, followed by "*text". For these fields, the keyword used
495 in the address-type, diagnostic-type, or MTA-name-type subfield
496 indicates the expected format of the address, status-code, or MTA-
506 Moore & Vaudreuil Standards Track [Page 9]
508 RFC 1894 Delivery Status Notifications January 1996
511 The "-type" subfields are defined as follows:
513 (a) An "address-type" specifies the format of a mailbox address. For
514 example, Internet mail addresses use the "rfc822" address-type.
518 (b) A "diagnostic-type" specifies the format of a status code. For
519 example, when a DSN field contains a reply code reported via the
520 Simple Mail Transfer Protocol [3], the "smtp" diagnostic-type is
523 diagnostic-type = atom
525 (c) An "MTA-name-type" specifies the format of an MTA name. For
526 example, for an SMTP server on an Internet host, the MTA name is the
527 domain name of that host, and the "dns" MTA-name-type is used.
531 Values for address-type, diagnostic-type, and MTA-name-type are
532 case-insensitive. Thus address-type values of "RFC822" and "rfc822"
535 The Internet Assigned Numbers Authority (IANA) will maintain a
536 registry of address-types, diagnostic-types, and MTA-name-types,
537 along with descriptions of the meanings and acceptable values of
538 each, or a reference to a one or more specifications that provide
539 such descriptions. (The "rfc822" address-type, "smtp" diagnostic-
540 type, and "dns" MTA-name-type are defined in [4].) Registration
541 forms for address-type, diagnostic-type, and MTA-name-type appear in
542 section 8 of this document.
544 IANA will not accept registrations for any address-type, diagnostic-
545 type, or MTA-name-type name that begins with "X-". These type names
546 are reserved for experimental use.
548 2.1.3 Lexical tokens imported from RFC 822
550 The following lexical tokens, defined in [6], are used in the ABNF
551 grammar for DSNs: atom, CHAR, comment, CR, CRLF, DIGIT, LF, linear-
552 white-space, SPACE, text. The date-time lexical token is defined in
562 Moore & Vaudreuil Standards Track [Page 10]
564 RFC 1894 Delivery Status Notifications January 1996
567 2.2 Per-Message DSN Fields
569 Some fields of a DSN apply to all of the delivery attempts described
570 by that DSN. These fields may appear at most once in any DSN. These
571 fields are used to correlate the DSN with the original message
572 transaction and to provide additional information which may be useful
576 [ original-envelope-id-field CRLF ]
577 reporting-mta-field CRLF
578 [ dsn-gateway-field CRLF ]
579 [ received-from-mta-field CRLF ]
580 [ arrival-date-field CRLF ]
581 *( extension-field CRLF )
583 2.2.1 The Original-Envelope-Id field
585 The optional Original-Envelope-Id field contains an "envelope
586 identifier" which uniquely identifies the transaction during which
587 the message was submitted, and was either (a) specified by the sender
588 and supplied to the sender's MTA, or (b) generated by the sender's
589 MTA and made available to the sender when the message was submitted.
590 Its purpose is to allow the sender (or her user agent) to associate
591 the returned DSN with the specific transaction in which the message
594 If such an envelope identifier was present in the envelope which
595 accompanied the message when it arrived at the Reporting MTA, it
596 SHOULD be supplied in the Original-Envelope-Id field of any DSNs
597 issued as a result of an attempt to deliver the message. Except when
598 a DSN is issued by the sender's MTA, an MTA MUST NOT supply this
599 field unless there is an envelope-identifier field in the envelope
600 which accompanied this message on its arrival at the Reporting MTA.
602 The Original-Envelope-Id field is defined as follows:
604 original-envelope-id-field =
605 "Original-Envelope-Id" ":" envelope-id
609 There may be at most one Original-Envelope-Id field per DSN.
611 The envelope-id is CASE-SENSITIVE. The DSN MUST preserve the
612 original case and spelling of the envelope-id.
618 Moore & Vaudreuil Standards Track [Page 11]
620 RFC 1894 Delivery Status Notifications January 1996
623 NOTE: The Original-Envelope-Id is NOT the same as the Message-Id from
624 the message header. The Message-Id identifies the content of the
625 message, while the Original-Envelope-Id identifies the transaction in
626 which the message is sent.
628 2.2.2 The Reporting-MTA DSN field
630 reporting-mta-field =
631 "Reporting-MTA" ":" mta-name-type ";" mta-name
635 The Reporting-MTA field is defined as follows:
637 A DSN describes the results of attempts to deliver, relay, or gateway
638 a message to one or more recipients. In all cases, the Reporting-MTA
639 is the MTA which attempted to perform the delivery, relay, or gateway
640 operation described in the DSN. This field is required.
642 Note that if an SMTP client attempts to relay a message to an SMTP
643 server and receives an error reply to a RCPT command, the client is
644 responsible for generating the DSN, and the client's domain name will
645 appear in the Reporting-MTA field. (The server's domain name will
646 appear in the Remote-MTA field.)
648 Note that the Reporting-MTA is not necessarily the MTA which actually
649 issued the DSN. For example, if an attempt to deliver a message
650 outside of the Internet resulted in a nondelivery notification which
651 was gatewayed back into Internet mail, the Reporting-MTA field of the
652 resulting DSN would be that of the MTA that originally reported the
653 delivery failure, not that of the gateway which converted the foreign
654 notification into a DSN. See Figure 2.
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676 RFC 1894 Delivery Status Notifications January 1996
679 sender's environment recipient's environment
680 ............................ ..........................................
683 +-----+ +--------+ +--------+ +---------+ +---------+ +------+
684 | | | | | | |Received-| | | | |
685 | |=>|Original|=>| |->| From |->|Reporting|-->|Remote|
686 | user| | MTA | | | | MTA | | MTA |<No| MTA |
687 |agent| +--------+ |Gateway | +---------+ +----v----+ +------+
689 | | <============| |<-------------------+
693 ...........................: :.........................................
695 Figure 2. DSNs in the presence of gateways
697 (1) message is gatewayed into recipient's environment
698 (2) attempt to relay message fails
699 (3) reporting-mta (in recipient's environment) returns nondelivery
701 (4) gateway translates foreign notification into a DSN
705 The mta-name portion of the Reporting-MTA field is formatted
706 according to the conventions indicated by the mta-name-type subfield.
707 If an MTA functions as a gateway between dissimilar mail environments
708 and thus is known by multiple names depending on the environment, the
709 mta-name subfield SHOULD contain the name used by the environment
710 from which the message was accepted by the Reporting-MTA.
712 Because the exact spelling of an MTA name may be significant in a
713 particular environment, MTA names are CASE-SENSITIVE.
715 2.2.3 The DSN-Gateway field
717 The DSN-Gateway field indicates the name of the gateway or MTA which
718 translated a foreign (non-Internet) delivery status notification into
719 this DSN. This field MUST appear in any DSN which was translated by
720 a gateway from a foreign system into DSN format, and MUST NOT appear
723 dsn-gateway-field = "DSN-Gateway" ":" mta-name-type ";" mta-name
730 Moore & Vaudreuil Standards Track [Page 13]
732 RFC 1894 Delivery Status Notifications January 1996
735 For gateways into Internet mail, the MTA-name-type will normally be
736 "smtp", and the mta-name will be the Internet domain name of the
739 2.2.4 The Received-From-MTA DSN field
741 The optional Received-From-MTA field indicates the name of the MTA
742 from which the message was received.
744 received-from-mta-field =
745 "Received-From-MTA" ":" mta-name-type ";" mta-name
747 If the message was received from an Internet host via SMTP, the
748 contents of the mta-name subfield SHOULD be the Internet domain name
749 supplied in the HELO or EHLO command, and the network address used by
750 the SMTP client SHOULD be included as a comment enclosed in
751 parentheses. (In this case, the MTA-name-type will be "smtp".)
753 The mta-name portion of the Received-From-MTA field is formatted
754 according to the conventions indicated by the MTA-name-type subfield.
756 Since case is significant in some mail systems, the exact spelling,
757 including case, of the MTA name SHOULD be preserved.
759 2.2.5 The Arrival-Date DSN field
761 The optional Arrival-Date field indicates the date and time at which
762 the message arrived at the Reporting MTA. If the Last-Attempt-Date
763 field is also provided in a per-recipient field, this can be used to
764 determine the interval between when the message arrived at the
765 Reporting MTA and when the report was issued for that recipient.
767 arrival-date-field = "Arrival-Date" ":" date-time
769 The date and time are expressed in RFC 822 'date-time' format, as
770 modified by [8]. Numeric timezones ([+/-]HHMM format) MUST be used.
772 2.3 Per-Recipient DSN fields
774 A DSN contains information about attempts to deliver a message to one
775 or more recipients. The delivery information for any particular
776 recipient is contained in a group of contiguous per-recipient fields.
777 Each group of per-recipient fields is preceded by a blank line.
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788 RFC 1894 Delivery Status Notifications January 1996
791 The syntax for the group of per-recipient fields is as follows:
794 per-recipient-fields =
795 [ original-recipient-field CRLF ]
796 final-recipient-field CRLF
799 [ remote-mta-field CRLF ]
800 [ diagnostic-code-field CRLF ]
801 [ last-attempt-date-field CRLF ]
802 [ will-retry-until-field CRLF ]
803 *( extension-field CRLF )
805 2.3.1 Original-Recipient field
807 The Original-Recipient field indicates the original recipient address
808 as specified by the sender of the message for which the DSN is being
811 original-recipient-field =
812 "Original-Recipient" ":" address-type ";" generic-address
814 generic-address = *text
816 The address-type field indicates the type of the original recipient
817 address. If the message originated within the Internet, the
818 address-type field field will normally be "rfc822", and the address
819 will be according to the syntax specified in [6]. The value
820 "unknown" should be used if the Reporting MTA cannot determine the
821 type of the original recipient address from the message envelope.
823 This field is optional. It should be included only if the sender-
824 specified recipient address was present in the message envelope, such
825 as by the SMTP extensions defined in [4]. This address is the same
826 as that provided by the sender and can be used to automatically
827 correlate DSN reports and message transactions.
829 2.3.2 Final-Recipient field
831 The Final-Recipient field indicates the recipient for which this set
832 of per-recipient fields applies. This field MUST be present in each
833 set of per-recipient data.
842 Moore & Vaudreuil Standards Track [Page 15]
844 RFC 1894 Delivery Status Notifications January 1996
847 The syntax of the field is as follows:
849 final-recipient-field =
850 "Final-Recipient" ":" address-type ";" generic-address
852 The generic-address subfield of the Final-Recipient field MUST
853 contain the mailbox address of the recipient (from the transport
854 envelope) as it was when the message was accepted for delivery by the
857 The Final-Recipient address may differ from the address originally
858 provided by the sender, because it may have been transformed during
859 forwarding and gatewaying into an totally unrecognizable mess.
860 However, in the absence of the optional Original-Recipient field, the
861 Final-Recipient field and any returned content may be the only
862 information available with which to correlate the DSN with a
863 particular message submission.
865 The address-type subfield indicates the type of address expected by
866 the reporting MTA in that context. Recipient addresses obtained via
867 SMTP will normally be of address-type "rfc822".
869 NOTE: The Reporting MTA is not expected to ensure that the address
870 actually conforms to the syntax conventions of the address-type.
871 Instead, it MUST report exactly the address received in the envelope,
872 unless that address contains characters such as CR or LF which may
873 not appear in a DSN field.
875 Since mailbox addresses (including those used in the Internet) may be
876 case sensitive, the case of alphabetic characters in the address MUST
881 The Action field indicates the action performed by the Reporting-MTA
882 as a result of its attempt to deliver the message to this recipient
883 address. This field MUST be present for each recipient named in the
886 The syntax for the action-field is:
888 action-field = "Action" ":" action-value
891 "failed" / "delayed" / "delivered" / "relayed" / "expanded"
898 Moore & Vaudreuil Standards Track [Page 16]
900 RFC 1894 Delivery Status Notifications January 1996
903 The action-value may be spelled in any combination of upper and lower
906 "failed" indicates that the message could not be delivered to the
907 recipient. The Reporting MTA has abandoned any attempts to
908 deliver the message to this recipient. No further
909 notifications should be expected.
911 "delayed" indicates that the Reporting MTA has so far been unable to
912 deliver or relay the message, but it will continue to
913 attempt to do so. Additional notification messages may be
914 issued as the message is further delayed or successfully
915 delivered, or if delivery attempts are later abandoned.
917 "delivered" indicates that the message was successfully delivered to
918 the recipient address specified by the sender, which
919 includes "delivery" to a mailing list exploder. It does
920 not indicate that the message has been read. This is a
921 terminal state and no further DSN for this recipient should
924 "relayed" indicates that the message has been relayed or gatewayed
925 into an environment that does not accept responsibility for
926 generating DSNs upon successful delivery. This action-
927 value SHOULD NOT be used unless the sender has requested
928 notification of successful delivery for this recipient.
930 "expanded" indicates that the message has been successfully delivered
931 to the recipient address as specified by the sender, and
932 forwarded by the Reporting-MTA beyond that destination to
933 multiple additional recipient addresses. An action-value
934 of "expanded" differs from "delivered" in that "expanded"
935 is not a terminal state. Further "failed" and/or "delayed"
936 notifications may be provided.
938 Using the terms "mailing list" and "alias" as defined in
939 [4], section 7.2.7: An action-value of "expanded" is only
940 to be used when the message is delivered to a multiple-
941 recipient "alias". An action-value of "expanded" SHOULD
942 NOT be used with a DSN issued on delivery of a message to a
945 NOTE ON ACTION VS. STATUS CODES: Although the 'action' field might
946 seem to be redundant with the 'status' field, this is not the case.
947 In particular, a "temporary failure" ("4") status code could be used
948 with an action-value of either "delayed" or "failed". For example,
949 assume that an SMTP client repeatedly tries to relay a message to the
950 mail exchanger for a recipient, but fails because a query to a domain
954 Moore & Vaudreuil Standards Track [Page 17]
956 RFC 1894 Delivery Status Notifications January 1996
959 name server timed out. After a few hours, it might issue a "delayed"
960 DSN to inform the sender that the message had not yet been delivered.
961 After a few days, the MTA might abandon its attempt to deliver the
962 message and return a "failed" DSN. The status code (which would
963 begin with a "4" to indicate "temporary failure") would be the same
966 Another example for which the action and status codes may appear
967 contradictory: If an MTA or mail gateway cannot deliver a message
968 because doing so would entail conversions resulting in an
969 unacceptable loss of information, it would issue a DSN with the
970 'action' field of "failure" and a status code of 'XXX'. If the
971 message had instead been relayed, but with some loss of information,
972 it might generate a DSN with the same XXX status-code, but with an
973 action field of "relayed".
977 The per-recipient Status field contains a transport-independent
978 status code which indicates the delivery status of the message to
979 that recipient. This field MUST be present for each delivery attempt
980 which is described by a DSN.
982 The syntax of the status field is:
984 status-field = "Status" ":" status-code
986 status-code = DIGIT "." 1*3DIGIT "." 1*3DIGIT
988 ; White-space characters and comments are NOT allowed within a
989 ; status-code, though a comment enclosed in parentheses MAY follow
990 ; the last numeric subfield of the status-code. Each numeric
991 ; subfield within the status-code MUST be expressed without
992 ; leading zero digits.
994 Status codes thus consist of three numerical fields separated by ".".
995 The first sub-field indicates whether the delivery attempt was
996 successful (2 = success, 4 = persistent temporary failure, 5 =
997 permanent failure). The second sub-field indicates the probable
998 source of any delivery anomalies, and the third sub-field denotes a
999 precise error condition, if known.
1001 The initial set of status-codes is defined in [5].
1010 Moore & Vaudreuil Standards Track [Page 18]
1012 RFC 1894 Delivery Status Notifications January 1996
1015 2.3.5 Remote-MTA field
1017 The value associated with the Remote-MTA DSN field is a printable
1018 ASCII representation of the name of the "remote" MTA that reported
1019 delivery status to the "reporting" MTA.
1021 remote-mta-field = "Remote-MTA" ":" mta-name-type ";" mta-name
1023 NOTE: The Remote-MTA field preserves the "while talking to"
1024 information that was provided in some pre-existing nondelivery
1027 This field is optional. It MUST NOT be included if no remote MTA was
1028 involved in the attempted delivery of the message to that recipient.
1030 2.3.6 Diagnostic-Code field
1032 For a "failed" or "delayed" recipient, the Diagnostic-Code DSN field
1033 contains the actual diagnostic code issued by the mail transport.
1034 Since such codes vary from one mail transport to another, the
1035 diagnostic-type subfield is needed to specify which type of
1036 diagnostic code is represented.
1038 diagnostic-code-field =
1039 "Diagnostic-Code" ":" diagnostic-type ";" *text
1041 NOTE: The information in the Diagnostic-Code field may be somewhat
1042 redundant with that from the Status field. The Status field is
1043 needed so that any DSN, regardless of origin, may be understood by
1044 any user agent or gateway that parses DSNs. Since the Status code
1045 will sometimes be less precise than the actual transport diagnostic
1046 code, the Diagnostic-Code field is provided to retain the latter
1047 information. Such information may be useful in a trouble ticket sent
1048 to the administrator of the Reporting MTA, or when tunneling foreign
1049 nondelivery reports through DSNs.
1051 If the Diagnostic Code was obtained from a Remote MTA during an
1052 attempt to relay the message to that MTA, the Remote-MTA field should
1053 be present. When interpreting a DSN, the presence of a Remote-MTA
1054 field indicates that the Diagnostic Code was issued by the Remote
1055 MTA. The absence of a Remote-MTA indicates that the Diagnostic Code
1056 was issued by the Reporting MTA.
1058 In addition to the Diagnostic-Code itself, additional textual
1059 description of the diagnostic, MAY appear in a comment enclosed in
1066 Moore & Vaudreuil Standards Track [Page 19]
1068 RFC 1894 Delivery Status Notifications January 1996
1071 This field is optional, because some mail systems supply no
1072 additional information beyond that which is returned in the 'action'
1073 and 'status' fields. However, this field SHOULD be included if
1074 transport-specific diagnostic information is available.
1076 2.3.7 Last-Attempt-Date field
1078 The Last-Attempt-Date field gives the date and time of the last
1079 attempt to relay, gateway, or deliver the message (whether successful
1080 or unsuccessful) by the Reporting MTA. This is not necessarily the
1081 same as the value of the Date field from the header of the message
1082 used to transmit this delivery status notification: In cases where
1083 the DSN was generated by a gateway, the Date field in the message
1084 header contains the time the DSN was sent by the gateway and the DSN
1085 Last-Attempt-Date field contains the time the last delivery attempt
1088 last-attempt-date-field = "Last-Attempt-Date" ":" date-time
1090 This field is optional. It MUST NOT be included if the actual date
1091 and time of the last delivery attempt are not available (which might
1092 be the case if the DSN were being issued by a gateway).
1094 The date and time are expressed in RFC 822 'date-time' format, as
1095 modified by [8]. Numeric timezones ([+/-]HHMM format) MUST be used.
1097 3.2.1.5 final-log-id field
1099 The "final-log-id" field gives the final-log-id of the message that
1100 was used by the final-mta. This can be useful as an index to the
1101 final-mta's log entry for that delivery attempt.
1103 final-log-id-field = "Final-Log-ID" ":" *text
1105 This field is optional.
1107 2.3.8 Will-Retry-Until field
1109 For DSNs of type "delayed", the Will-Retry-Until field gives the date
1110 after which the Reporting MTA expects to abandon all attempts to
1111 deliver the message to that recipient. The Will-Retry-Until field is
1112 optional for "delay" DSNs, and MUST NOT appear in other DSNs.
1114 will-retry-until-field = "Will-Retry-Until" ":" date-time
1116 The date and time are expressed in RFC 822 'date-time' format, as
1117 modified by [8]. Numeric timezones ([+/-]HHMM format) MUST be used.
1122 Moore & Vaudreuil Standards Track [Page 20]
1124 RFC 1894 Delivery Status Notifications January 1996
1127 2.4 Extension fields
1129 Additional per-message or per-recipient DSN fields may be defined in
1130 the future by later revisions or extensions to this specification.
1131 Extension-field names beginning with "X-" will never be defined as
1132 standard fields; such names are reserved for experimental use. DSN
1133 field names NOT beginning with "X-" MUST be registered with the
1134 Internet Assigned Numbers Authority (IANA) and published in an RFC.
1136 Extension DSN fields may be defined for the following reasons:
1138 (a) To allow additional information from foreign delivery status
1139 reports to be tunneled through Internet DSNs. The names of such
1140 DSN fields should begin with an indication of the foreign
1141 environment name (e.g. X400-Physical-Forwarding-Address).
1143 (b) To allow the transmission of diagnostic information which is
1144 specific to a particular mail transport protocol. The names of
1145 such DSN fields should begin with an indication of the mail
1146 transport being used (e.g. SMTP-Remote-Recipient-Address). Such
1147 fields should be used for diagnostic purposes only and not by
1148 user agents or mail gateways.
1150 (c) To allow transmission of diagnostic information which is specific
1151 to a particular message transfer agent (MTA). The names of such
1152 DSN fields should begin with an indication of the MTA
1153 implementation which produced the DSN. (e.g. Foomail-Queue-ID).
1155 MTA implementors are encouraged to provide adequate information, via
1156 extension fields if necessary, to allow an MTA maintainer to
1157 understand the nature of correctable delivery failures and how to fix
1158 them. For example, if message delivery attempts are logged, the DSN
1159 might include information which allows the MTA maintainer to easily
1160 find the log entry for a failed delivery attempt.
1162 If an MTA developer does not wish to register the meanings of such
1163 extension fields, "X-" fields may be used for this purpose. To avoid
1164 name collisions, the name of the MTA implementation should follow the
1165 "X-", (e.g. "X-Foomail-Log-ID").
1167 3. Conformance and Usage Requirements
1169 An MTA or gateway conforms to this specification if it generates DSNs
1170 according to the protocol defined in this memo. For MTAs and
1171 gateways that do not support requests for positive delivery
1172 notification (such as in [4]), it is sufficient that delivery failure
1173 reports use this protocol.
1178 Moore & Vaudreuil Standards Track [Page 21]
1180 RFC 1894 Delivery Status Notifications January 1996
1183 A minimal implementation of this specification need generate only the
1184 Reporting-MTA per-message field, and the Final-Recipient, Action, and
1185 Status fields for each attempt to deliver a message to a recipient
1186 described by the DSN. Generation of the other fields, when
1187 appropriate, is strongly recommended.
1189 MTAs and gateways MUST NOT generate the Original-Recipient field of a
1190 DSN unless the mail transfer protocol provides the address originally
1191 specified by the sender at the time of submission. (Ordinary SMTP
1192 does not make that guarantee, but the SMTP extension defined in [4]
1193 permits such information to be carried in the envelope if it is
1196 Each sender-specified recipient address SHOULD result in at most one
1197 "delivered" or "failed" DSN for that recipient. If a positive DSN is
1198 requested (e.g. one using NOTIFY=SUCCESS in SMTP) for a recipient
1199 that is forwarded to multiple recipients of an "alias" (as defined in
1200 [4], section 7.2.7), the forwarding MTA SHOULD normally issue a
1201 "expanded" DSN for the originally-specified recipient and not
1202 propagate the request for a DSN to the forwarding addresses.
1203 Alternatively, the forwarding MTA MAY relay the request for a DSN to
1204 exactly one of the forwarding addresses and not propagate the request
1207 By contrast, successful submission of a message to a mailing list
1208 exploder is considered final delivery of the message. Upon delivery
1209 of a message to a recipient address corresponding to a mailing list
1210 exploder, the Reporting MTA SHOULD issue an appropriate DSN exactly
1211 as if the recipient address were that of an ordinary mailbox.
1213 NOTE: This is actually intended to make DSNs usable by mailing lists
1214 themselves. Any message sent to a mailing list subscriber should
1215 have its envelope return address pointing to the list maintainer [see
1216 RFC 1123, section 5.3.7(E)]. Since DSNs are sent to the envelope
1217 return address, all DSNs resulting from delivery to the recipients of
1218 a mailing list will be sent to the list maintainer. The list
1219 maintainer may elect to mechanically process DSNs upon receipt, and
1220 thus automatically delete invalid addresses from the list. (See
1221 section 7 of this memo.)
1223 This specification places no restrictions on the processing of DSNs
1224 received by user agents or distribution lists.
1226 4. Security Considerations
1228 The following security considerations apply when using DSNs:
1234 Moore & Vaudreuil Standards Track [Page 22]
1236 RFC 1894 Delivery Status Notifications January 1996
1241 DSNs may be forged as easily as ordinary Internet electronic mail.
1242 User agents and automatic mail handling facilities (such as mail
1243 distribution list exploders) that wish to make automatic use of DSNs
1244 should take appropriate precautions to minimize the potential damage
1245 from denial-of-service attacks.
1247 Security threats related to forged DSNs include the sending of:
1249 (a) A falsified delivery notification when the message is not delivered
1250 to the indicated recipient,
1251 (b) A falsified non-delivery notification when the message was in fact
1252 delivered to the indicated recipient,
1253 (c) A falsified Final-Recipient address,
1254 (d) A falsified Remote-MTA identification,
1255 (e) A falsified relay notification when the message is "dead ended".
1256 (f) Unsolicited DSNs
1260 Another dimension of security is confidentiality. There may be cases
1261 in which a message recipient is autoforwarding messages but does not
1262 wish to divulge the address to which the messages are autoforwarded.
1263 The desire for such confidentiality will probably be heightened as
1264 "wireless mailboxes", such as pagers, become more widely used as
1265 autoforward addresses.
1267 MTA authors are encouraged to provide a mechanism which enables the
1268 end user to preserve the confidentiality of a forwarding address.
1269 Depending on the degree of confidentiality required, and the nature
1270 of the environment to which a message were being forwarded, this
1271 might be accomplished by one or more of:
1273 (a) issuing a "relayed" DSN (if a positive DSN was requested) when a
1274 message is forwarded to a confidential forwarding address, and
1275 disabling requests for positive DSNs for the forwarded message,
1277 (b) declaring the message to be delivered, issuing a "delivered" DSN,
1278 re-sending the message to the confidential forwarding address, and
1279 arranging for no DSNs to be issued for the re-sent message,
1281 (c) omitting "Remote-*" or extension fields of a DSN whenever they would
1282 otherwise contain confidential information (such as a confidential
1283 forwarding address),
1285 (d) for messages forwarded to a confidential address, setting the
1286 envelope return address (e.g. SMTP MAIL FROM address) to the NULL
1290 Moore & Vaudreuil Standards Track [Page 23]
1292 RFC 1894 Delivery Status Notifications January 1996
1295 reverse-path ("<>") (so that no DSNs would be sent from a downstream
1296 MTA to the original sender),
1298 (e) for messages forwarded to a confidential address, disabling delivery
1299 notifications for the forwarded message (e.g. if the "next-hop" MTA
1300 uses ESMTP and supports the DSN extension, by using the NOTIFY=NEVER
1301 parameter to the RCPT command), or
1303 (f) when forwarding mail to a confidential address, having the
1304 forwarding MTA rewrite the envelope return address for the forwarded
1305 message and attempt delivery of that message as if the forwarding
1306 MTA were the originator. On its receipt of final delivery status,
1307 the forwarding MTA would issue a DSN to the original sender.
1309 In general, any optional DSN field may be omitted if the Reporting
1310 MTA site determines that inclusion of the field would impose too
1311 great a compromise of site confidentiality. The need for such
1312 confidentiality must be balanced against the utility of the omitted
1313 information in trouble reports and DSNs gatewayed to foreign
1316 Implementors are cautioned that many existing MTAs will send
1317 nondelivery notifications to a return address in the message header
1318 (rather than to the one in the envelope), in violation of SMTP and
1319 other protocols. If a message is forwarded through such an MTA, no
1320 reasonable action on the part of the forwarding MTA will prevent the
1321 downstream MTA from compromising the forwarding address. Likewise,
1322 if the recipient's MTA automatically responds to messages based on a
1323 request in the message header (such as the nonstandard, but widely
1324 used, Return-Receipt-To extension header), it will also compromise
1325 the forwarding address.
1329 Within the framework of today's internet mail, the DSNs defined in
1330 this memo provide valuable information to the mail user; however,
1331 even a "failed" DSN can not be relied upon as a guarantee that a
1332 message was not received by the recipient. Even if DSNs are not
1333 actively forged, conditions exist under which a message can be
1334 delivered despite the fact that a failure DSN was issued.
1346 Moore & Vaudreuil Standards Track [Page 24]
1348 RFC 1894 Delivery Status Notifications January 1996
1351 For example, a race condition in the SMTP protocol allows for the
1352 duplication of messages if the connection is dropped following a
1353 completed DATA command, but before a response is seen by the SMTP
1354 client. This will cause the SMTP client to retransmit the message,
1355 even though the SMTP server has already accepted it.[9] If one of
1356 those delivery attempts succeeds and the other one fails, a "failed"
1357 DSN could be issued even though the message actually reached the
1402 Moore & Vaudreuil Standards Track [Page 25]
1404 RFC 1894 Delivery Status Notifications January 1996
1407 5. Appendix - collected grammar
1409 NOTE: The following lexical tokens are defined in RFC 822: atom,
1410 CHAR, comment, CR, CRLF, DIGIT, LF, linear-white-space, SPACE, text.
1411 The date-time lexical token is defined in [8].
1413 action-field = "Action" ":" action-value
1416 "failed" / "delayed" / "delivered" / "relayed" / "expanded"
1420 arrival-date-field = "Arrival-Date" ":" date-time
1422 delivery-status-content =
1423 per-message-fields 1*( CRLF per-recipient-fields )
1425 diagnostic-code-field =
1426 "Diagnostic-Code" ":" diagnostic-type ";" *text
1428 diagnostic-type = atom
1430 dsn-gateway-field = "DSN-Gateway" ":" mta-name-type ";" mta-name
1434 extension-field = extension-field-name ":" *text
1436 extension-field-name = atom
1438 final-recipient-field =
1439 "Final-Recipient" ":" address-type ";" generic-address
1441 generic-address = *text
1443 last-attempt-date-field = "Last-Attempt-Date" ":" date-time
1447 mta-name-type = atom
1449 original-envelope-id-field =
1450 "Original-Envelope-Id" ":" envelope-id
1452 original-recipient-field =
1453 "Original-Recipient" ":" address-type ";" generic-address
1458 Moore & Vaudreuil Standards Track [Page 26]
1460 RFC 1894 Delivery Status Notifications January 1996
1463 per-message-fields =
1464 [ original-envelope-id-field CRLF ]
1465 reporting-mta-field CRLF
1466 [ dsn-gateway-field CRLF ]
1467 [ received-from-mta-field CRLF ]
1468 [ arrival-date-field CRLF ]
1469 *( extension-field CRLF )
1471 per-recipient-fields =
1472 [ original-recipient-field CRLF ]
1473 final-recipient-field CRLF
1476 [ remote-mta-field CRLF ]
1477 [ diagnostic-code-field CRLF ]
1478 [ last-attempt-date-field CRLF ]
1479 [ will-retry-until-field CRLF ]
1480 *( extension-field CRLF )
1482 received-from-mta-field =
1483 "Received-From-MTA" ":" mta-name-type ";" mta-name
1485 remote-mta-field = "Remote-MTA" ":" mta-name-type ";" mta-name
1487 reporting-mta-field =
1488 "Reporting-MTA" ":" mta-name-type ";" mta-name
1490 status-code = DIGIT "." 1*3DIGIT "." 1*3DIGIT
1492 ; White-space characters and comments are NOT allowed within a
1493 ; status-code, though a comment enclosed in parentheses MAY follow
1494 ; the last numeric subfield of the status-code. Each numeric
1495 ; subfield within the status-code MUST be expressed without
1496 ; leading zero digits.
1498 status-field = "Status" ":" status-code
1500 will-retry-until-field = "Will-Retry-Until" ":" date-time
1514 Moore & Vaudreuil Standards Track [Page 27]
1516 RFC 1894 Delivery Status Notifications January 1996
1519 6. Appendix - Guidelines for gatewaying DSNs
1521 NOTE: This section provides non-binding recommendations for the
1522 construction of mail gateways that wish to provide semi-transparent
1523 delivery reports between the Internet and another electronic mail
1524 system. Specific DSN gateway requirements for a particular pair of
1525 mail systems may be defined by other documents.
1527 6.1 Gatewaying from other mail systems to DSNs
1529 A mail gateway may issue a DSN to convey the contents of a "foreign"
1530 delivery or non-delivery notification over Internet mail. When there
1531 are appropriate mappings from the foreign notification elements to
1532 DSN fields, the information may be transmitted in those DSN fields.
1533 Additional information (such as might be useful in a trouble ticket
1534 or needed to tunnel the foreign notification through the Internet)
1535 may be defined in extension DSN fields. (Such fields should be given
1536 names that identify the foreign mail protocol, e.g. X400-* for X.400
1537 NDN or DN protocol elements)
1539 The gateway must attempt to supply reasonable values for the
1540 Reporting-MTA, Final-Recipient, Action, and Status fields. These
1541 will normally be obtained by translating the values from the remote
1542 delivery or non-delivery notification into their Internet-style
1543 equivalents. However, some loss of information is to be expected.
1544 For example, the set of status-codes defined for DSNs may not be
1545 adequate to fully convey the delivery diagnostic code from the
1546 foreign system. The gateway should assign the most precise code
1547 which describes the failure condition, falling back on "generic"
1548 codes such as 2.0.0 (success), 4.0.0 (temporary failure), and 5.0.0
1549 (permanent failure) when necessary. The actual foreign diagnostic
1550 code should be retained in the Diagnostic-Code field (with an
1551 appropriate diagnostic-type value) for use in trouble tickets or
1554 The sender-specified recipient address, and the original envelope-id,
1555 if present in the foreign transport envelope, should be preserved in
1556 the Original-Recipient and Original-Envelope-ID fields.
1558 The gateway should also attempt to preserve the "final" recipient
1559 addresses and MTA names from the foreign system. Whenever possible,
1560 foreign protocol elements should be encoded as meaningful printable
1563 For DSNs produced from foreign delivery or nondelivery notifications,
1564 the name of the gateway MUST appear in the DSN-Gateway field of the
1570 Moore & Vaudreuil Standards Track [Page 28]
1572 RFC 1894 Delivery Status Notifications January 1996
1575 6.2 Gatewaying from DSNs to other mail systems
1577 It may be possible to gateway DSNs from the Internet into a foreign
1578 mail system. The primary purpose of such gatewaying is to convey
1579 delivery status information in a form that is usable by the
1580 destination system. A secondary purpose is to allow "tunneling" of
1581 DSNs through foreign mail systems, in case the DSN may be gatewayed
1582 back into the Internet.
1584 In general, the recipient of the DSN (i.e., the sender of the
1585 original message) will want to know, for each recipient: the closest
1586 available approximation to the original recipient address, the
1587 delivery status (success, failure, or temporary failure), and for
1588 failed deliveries, a diagnostic code that describes the reason for
1591 If possible, the gateway should attempt to preserve the Original-
1592 Recipient address and Original-Envelope-ID (if present), in the
1593 resulting foreign delivery status report.
1595 When reporting delivery failures, if the diagnostic-type subfield of
1596 the Diagnostic-Code field indicates that the original diagnostic code
1597 is understood by the destination environment, the information from
1598 the Diagnostic-Code field should be used. Failing that, the
1599 information in the Status field should be mapped into the closest
1600 available diagnostic code used in the destination environment.
1602 If it is possible to tunnel a DSN through the destination
1603 environment, the gateway specification may define a means of
1604 preserving the DSN information in the delivery status reports used by
1626 Moore & Vaudreuil Standards Track [Page 29]
1628 RFC 1894 Delivery Status Notifications January 1996
1631 7. Appendix - Guidelines for use of DSNs by mailing list exploders
1633 NOTE: This section pertains only to the use of DSNs by "mailing
1634 lists" as defined in [4], section 7.2.7.
1636 DSNs are designed to be used by mailing list exploders to allow them
1637 to detect and automatically delete recipients for whom mail delivery
1640 When forwarding a message to list subscribers, the mailing list
1641 exploder should always set the envelope return address (e.g. SMTP
1642 MAIL FROM address) to point to a special address which is set up to
1643 received nondelivery reports. A "smart" mailing list exploder can
1644 therefore intercept such nondelivery reports, and if they are in the
1645 DSN format, automatically examine them to determine for which
1646 recipients a message delivery failed or was delayed.
1648 The Original-Recipient field should be used if available, since it
1649 should exactly match the subscriber address known to the list. If
1650 the Original-Recipient field is not available, the recipient field
1651 may resemble the list subscriber address. Often, however, the list
1652 subscriber will have forwarded his mail to a different address, or
1653 the address may be subject to some re-writing, so heuristics may be
1654 required to successfully match an address from the recipient field.
1655 Care is needed in this case to minimize the possibility of false
1658 The reason for delivery failure can be obtained from the Status and
1659 Action fields, and from the Diagnostic-Code field (if the status-type
1660 is recognized). Reports for recipients with action values other than
1661 "failed" can generally be ignored; in particular, subscribers should
1662 not be removed from a list due to "delayed" reports.
1664 In general, almost any failure status code (even a "permanent" one)
1665 can result from a temporary condition. It is therefore recommended
1666 that a list exploder not delete a subscriber based on any single
1667 failure DSN (regardless of the status code), but only on the
1668 persistence of delivery failure over a period of time.
1670 However, some kinds of failures are less likely than others to have
1671 been caused by temporary conditions, and some kinds of failures are
1672 more likely to be noticed and corrected quickly than others. Once
1673 more precise status codes are defined, it may be useful to
1674 differentiate between the status codes when deciding whether to
1675 delete a subscriber. For example, on a list with a high message
1676 volume, it might be desirable to temporarily suspend delivery to a
1677 recipient address which causes repeated "temporary" failures, rather
1678 than simply deleting the recipient. The duration of the suspension
1682 Moore & Vaudreuil Standards Track [Page 30]
1684 RFC 1894 Delivery Status Notifications January 1996
1687 might depend on the type of error. On the other hand, a "user
1688 unknown" error which persisted for several days could be considered a
1689 reliable indication that address were no longer valid.
1691 8. Appendix - IANA registration forms for DSN types
1693 The forms below are for use when registering a new address-type,
1694 diagnostic-type, or MTA-name-type with the Internet Assigned Numbers
1695 Authority (IANA). Each piece of information requested by a
1696 registration form may be satisfied either by providing the
1697 information on the form itself, or by including a reference to a
1698 published, publicly available specification which includes the
1699 necessary information. IANA MAY reject DSN type registrations
1700 because of incomplete registration forms, imprecise specifications,
1701 or inappropriate type names.
1703 To register a DSN type, complete the applicable form below and send
1704 it via Internet electronic mail to <IANA@IANA.ORG>.
1706 8.1 IANA registration form for address-type
1708 A registration for a DSN address-type MUST include the following
1711 (a) The proposed address-type name.
1713 (b) The syntax for mailbox addresses of this type, specified using BNF,
1714 regular expressions, ASN.1, or other non-ambiguous language.
1716 (c) If addresses of this type are not composed entirely of graphic
1717 characters from the US-ASCII repertoire, a specification for how
1718 they are to be encoded as graphic US-ASCII characters in a DSN
1719 Original-Recipient or Final-Recipient DSN field.
1721 (d) [optional] A specification for how addresses of this type are to be
1722 translated to and from Internet electronic mail addresses.
1724 8.2 IANA registration form for diagnostic-type
1726 A registration for a DSN address-type MUST include the following
1729 (a) The proposed diagnostic-type name.
1731 (b) A description of the syntax to be used for expressing diagnostic
1732 codes of this type as graphic characters from the US-ASCII
1738 Moore & Vaudreuil Standards Track [Page 31]
1740 RFC 1894 Delivery Status Notifications January 1996
1743 (c) A list of valid diagnostic codes of this type and the meaning of
1746 (d) [optional] A specification for mapping from diagnostic codes of this
1747 type to DSN status codes (as defined in [5]).
1749 8.3 IANA registration form for MTA-name-type
1751 A registration for a DSN MTA-name-type must include the following
1754 (a) The proposed MTA-name-type name.
1756 (b) A description of the syntax of MTA names of this type, using BNF,
1757 regular expressions, ASN.1, or other non-ambiguous language.
1759 (c) If MTA names of this type do not consist entirely of graphic
1760 characters from the US-ASCII repertoire, a specification for how an
1761 MTA name of this type should be expressed as a sequence of graphic
1762 US-ASCII characters.
1794 Moore & Vaudreuil Standards Track [Page 32]
1796 RFC 1894 Delivery Status Notifications January 1996
1799 9. Appendix - Examples
1801 NOTE: These examples are provided as illustration only, and are not
1802 considered part of the DSN protocol specification. If an example
1803 conflicts with the protocol definition above, the example is wrong.
1805 Likewise, the use of *-type subfield names or extension fields in
1806 these examples is not to be construed as a definition for those type
1807 names or extension fields.
1809 These examples were manually translated from bounced messages using
1810 whatever information was available.
1850 Moore & Vaudreuil Standards Track [Page 33]
1852 RFC 1894 Delivery Status Notifications January 1996
1855 9.1 This is a simple DSN issued after repeated attempts
1856 to deliver a message failed. In this case, the DSN is
1857 issued by the same MTA from which the message was originated.
1860 Date: Thu, 7 Jul 1994 17:16:05 -0400
1861 From: Mail Delivery Subsystem <MAILER-DAEMON@CS.UTK.EDU>
1862 Message-Id: <199407072116.RAA14128@CS.UTK.EDU>
1863 Subject: Returned mail: Cannot send message for 5 days
1864 To: <owner-info-mime@cs.utk.edu>
1866 Content-Type: multipart/report; report-type=delivery-status;
1867 boundary="RAA14128.773615765/CS.UTK.EDU"
1869 --RAA14128.773615765/CS.UTK.EDU
1871 The original message was received at Sat, 2 Jul 1994 17:10:28 -0400
1874 ----- The following addresses had delivery problems -----
1875 <louisl@larry.slip.umd.edu> (unrecoverable error)
1877 ----- Transcript of session follows -----
1878 <louisl@larry.slip.umd.edu>... Deferred: Connection timed out
1879 with larry.slip.umd.edu.
1880 Message could not be delivered for 5 days
1881 Message will be deleted from queue
1883 --RAA14128.773615765/CS.UTK.EDU
1884 content-type: message/delivery-status
1886 Reporting-MTA: dns; cs.utk.edu
1888 Original-Recipient: rfc822;louisl@larry.slip.umd.edu
1889 Final-Recipient: rfc822;louisl@larry.slip.umd.edu
1892 Diagnostic-Code: smtp; 426 connection timed out
1893 Last-Attempt-Date: Thu, 7 Jul 1994 17:15:49 -0400
1895 --RAA14128.773615765/CS.UTK.EDU
1896 content-type: message/rfc822
1898 [original message goes here]
1899 --RAA14128.773615765/CS.UTK.EDU--
1906 Moore & Vaudreuil Standards Track [Page 34]
1908 RFC 1894 Delivery Status Notifications January 1996
1911 9.2 This is another DSN issued by the sender's MTA, which
1912 contains details of multiple delivery attempts. Some of
1913 these were detected locally, and others by a remote MTA.
1916 Date: Fri, 8 Jul 1994 09:21:47 -0400
1917 From: Mail Delivery Subsystem <MAILER-DAEMON@CS.UTK.EDU>
1918 Subject: Returned mail: User unknown
1919 To: <owner-ups-mib@CS.UTK.EDU>
1921 Content-Type: multipart/report; report-type=delivery-status;
1922 boundary="JAA13167.773673707/CS.UTK.EDU"
1924 --JAA13167.773673707/CS.UTK.EDU
1925 content-type: text/plain; charset=us-ascii
1927 ----- The following addresses had delivery problems -----
1928 <arathib@vnet.ibm.com> (unrecoverable error)
1929 <wsnell@sdcc13.ucsd.edu> (unrecoverable error)
1931 --JAA13167.773673707/CS.UTK.EDU
1932 content-type: message/delivery-status
1934 Reporting-MTA: dns; cs.utk.edu
1936 Original-Recipient: rfc822;arathib@vnet.ibm.com
1937 Final-Recipient: rfc822;arathib@vnet.ibm.com
1939 Status: 5.0.0 (permanent failure)
1940 Diagnostic-Code: smtp;
1941 550 'arathib@vnet.IBM.COM' is not a registered gateway user
1942 Remote-MTA: dns; vnet.ibm.com
1944 Original-Recipient: rfc822;johnh@hpnjld.njd.hp.com
1945 Final-Recipient: rfc822;johnh@hpnjld.njd.hp.com
1947 Status: 4.0.0 (hpnjld.njd.jp.com: host name lookup failure)
1949 Original-Recipient: rfc822;wsnell@sdcc13.ucsd.edu
1950 Final-Recipient: rfc822;wsnell@sdcc13.ucsd.edu
1953 Diagnostic-Code: smtp; 550 user unknown
1954 Remote-MTA: dns; sdcc13.ucsd.edu
1956 --JAA13167.773673707/CS.UTK.EDU
1957 content-type: message/rfc822
1962 Moore & Vaudreuil Standards Track [Page 35]
1964 RFC 1894 Delivery Status Notifications January 1996
1967 [original message goes here]
1968 --JAA13167.773673707/CS.UTK.EDU--
1971 9.3 A delivery report generated by Message Router (MAILBUS) and
1972 gatewayed by PMDF_MR to a DSN. In this case the gateway did not
1973 have sufficient information to supply an original-recipient address.
1977 Disclose-recipients: prohibited
1978 Date: Fri, 08 Jul 1994 09:21:25 -0400 (EDT)
1979 From: Message Router Submission Agent <AMMGR@corp.timeplex.com>
1980 Subject: Status of : Re: Battery current sense
1981 To: owner-ups-mib@CS.UTK.EDU
1982 Message-id: <01HEGJ0WNBY28Y95LN@mr.timeplex.com>
1984 content-type: multipart/report; report-type=delivery-status;
1985 boundary="84229080704991.122306.SYS30"
1987 --84229080704991.122306.SYS30
1988 content-type: text/plain
1990 Invalid address - nair_s
1991 %DIR-E-NODIRMTCH, No matching Directory Entry found
1993 --84229080704991.122306.SYS30
1994 content-type: message/delivery-status
1996 Reporting-MTA: mailbus; SYS30
1998 Final-Recipient: unknown; nair_s
1999 Status: 5.0.0 (unknown permanent failure)
2002 --84229080704991.122306.SYS30--
2018 Moore & Vaudreuil Standards Track [Page 36]
2020 RFC 1894 Delivery Status Notifications January 1996
2023 9.4 A delay report from a multiprotocol MTA. Note that there is no
2024 returned content, so no third body part appears in the DSN.
2026 From: <postmaster@nsfnet-relay.ac.uk>
2027 Message-Id: <199407092338.TAA23293@CS.UTK.EDU>
2028 Received: from nsfnet-relay.ac.uk by sun2.nsfnet-relay.ac.uk
2029 id <g.12954-0@sun2.nsfnet-relay.ac.uk>;
2030 Sun, 10 Jul 1994 00:36:51 +0100
2031 To: owner-info-mime@cs.utk.edu
2032 Date: Sun, 10 Jul 1994 00:36:51 +0100
2033 Subject: WARNING: message delayed at "nsfnet-relay.ac.uk"
2034 content-type: multipart/report; report-type=delivery-status;
2038 content-type: text/plain
2040 The following message:
2042 UA-ID: Reliable PC (...
2043 Q-ID: sun2.nsf:77/msg.11820-0
2045 has not been delivered to the intended recipient:
2047 thomas@de-montfort.ac.uk
2049 despite repeated delivery attempts over the past 24 hours.
2051 The usual cause of this problem is that the remote system is
2052 temporarily unavailable.
2054 Delivery will continue to be attempted up to a total elapsed
2055 time of 168 hours, ie 7 days.
2057 You will be informed if delivery proves to be impossible
2060 Please quote the Q-ID in any queries regarding this mail.
2063 content-type: message/delivery-status
2065 Reporting-MTA: dns; sun2.nsfnet-relay.ac.uk
2067 Final-Recipient: rfc822;thomas@de-montfort.ac.uk
2068 Status: 4.0.0 (unknown temporary failure)
2074 Moore & Vaudreuil Standards Track [Page 37]
2076 RFC 1894 Delivery Status Notifications January 1996
2083 The authors wish to thank the following people for their reviews of
2084 earlier drafts of this document and their suggestions for
2085 improvement: Eric Allman, Harald Alvestrand, Allan Cargille, Jim
2086 Conklin, Peter Cowen, Dave Crocker, Roger Fajman, Ned Freed, Marko
2087 Kaittola, Steve Kille, John Klensin, John Gardiner Myers, Mark
2088 Nahabedian, Julian Onions, Jacob Palme, Jean Charles Roy, and Gregory
2093 [1] Borenstein, N., Freed, N. "Multipurpose Internet Mail Extensions",
2094 RFC 1521, Bellcore, Innosoft, September 1993.
2096 [2] Vaudreuil, G., "The Multipart/Report Content Type for the Reporting
2097 of Mail System Administrative Messages", RFC 1892, Octal Network
2098 Services, January 1996.
2100 [3] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
2101 USC/Information Sciences Institute, August 1982.
2103 [4] Moore, K., "SMTP Service Extension for Delivery Status
2104 Notifications", RFC 1891, University of Tennessee, January 1996.
2106 [5] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC 1893, Octal
2107 Network Services, January 1996.
2109 [6] Crocker, D., "Standard for the Format of ARPA Internet Text
2110 Messages", STD 11, RFC 822, UDEL, August 1982.
2112 [7] Moore, K. "MIME (Multipurpose Internet Mail Extensions) Part Two:
2113 Message Header Extensions for Non-Ascii Text", RFC 1522, University
2114 of Tennessee, September 1993.
2116 [8] Braden, R. (ed.) "Requirements for Internet Hosts - Application and
2117 Support", STD 3, RFC 1123, USC/Information Sciences Institute,
2120 [9] Partridge, C., "Duplicate Messages and SMTP", RFC 1047, BBN,
2130 Moore & Vaudreuil Standards Track [Page 38]
2132 RFC 1894 Delivery Status Notifications January 1996
2135 11. Authors' Addresses
2138 University of Tennessee
2140 Knoxville, TN 37996-1301
2143 EMail: moore@cs.utk.edu
2144 Phone: +1 615 974 3126
2145 Fax: +1 615 974 8296
2148 Gregory M. Vaudreuil
2149 Octel Network Services
2150 17080 Dallas Parkway
2151 Dallas, TX 75248-1905
2154 EMail: Greg.Vaudreuil@Octel.Com
2186 Moore & Vaudreuil Standards Track [Page 39]