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rfc:rfc3798

Network Working Group T. Hansen, Ed. Request for Comments: 3798 AT&T Laboratories Obsoletes: 2298 G. Vaudreuil, Ed. Updates: 3461, 2046 Lucent Technologies Category: Standards Track May 2004

                 Message Disposition Notification

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

 This memo defines a MIME content-type that may be used by a mail user
 agent (MUA) or electronic mail gateway to report the disposition of a
 message after it has been successfully delivered to a recipient.
 This content-type is intended to be machine-processable.  Additional
 message headers are also defined to permit Message Disposition
 Notifications (MDNs) to be requested by the sender of a message.  The
 purpose is to extend Internet Mail to support functionality often
 found in other messaging systems, such as X.400 and the proprietary
 "LAN-based" systems, and often referred to as "read receipts,"
 "acknowledgements", or "receipt notifications."  The intention is to
 do this while respecting privacy concerns, which have often been
 expressed when such functions have been discussed in the past.
 Because many messages are sent between the Internet and other
 messaging systems (such as X.400 or the proprietary "LAN-based"
 systems), the MDN protocol is designed to be useful in a multi-
 protocol messaging environment.  To this end, the protocol described
 in this memo provides for the carriage of "foreign" addresses, in
 addition to those normally used in Internet Mail.  Additional
 attributes may also be defined to support "tunneling" of foreign
 notifications through Internet Mail.

Hansen & Vaudreuil Standards Track [Page 1] RFC 3798 Message Disposition Notification May 2004

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Purposes . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Requirements . . . . . . . . . . . . . . . . . . . . . .  3
     1.3.  Terminology. . . . . . . . . . . . . . . . . . . . . . .  4
 2.  Requesting Message Disposition Notifications . . . . . . . . .  4
     2.1.  The Disposition-Notification-To Header . . . . . . . . .  4
     2.2.  The Disposition-Notification-Options Header. . . . . . .  6
     2.3.  The Original-Recipient Header. . . . . . . . . . . . . .  7
     2.4.  Use with the Message/Partial Content Type. . . . . . . .  8
 3.  FORMAT OF A MESSAGE DISPOSITION NOTIFICATION . . . . . . . . .  8
     3.1.  The message/disposition-notification content-type. . . .  9
     3.2.  Message/disposition-notification Fields. . . . . . . . . 11
     3.3.  Extension-fields . . . . . . . . . . . . . . . . . . . . 16
 4.  Timeline of Events . . . . . . . . . . . . . . . . . . . . . . 17
 5.  Conformance and Usage Requirements . . . . . . . . . . . . . . 18
 6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 19
     6.1.  Forgery. . . . . . . . . . . . . . . . . . . . . . . . . 19
     6.2.  Privacy. . . . . . . . . . . . . . . . . . . . . . . . . 19
     6.3.  Non-Repudiation. . . . . . . . . . . . . . . . . . . . . 20
     6.4.  Mail Bombing . . . . . . . . . . . . . . . . . . . . . . 20
 7.  Collected Grammar. . . . . . . . . . . . . . . . . . . . . . . 20
 8.  Guidelines for Gatewaying MDNS . . . . . . . . . . . . . . . . 22
     8.1.  Gatewaying from other mail systems to MDNs . . . . . . . 23
     8.2.  Gatewaying from MDNs to other mail systems . . . . . . . 23
     8.3.  Gatewaying of MDN-requests to other mail systems . . . . 24
 9.  Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
 10. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 25
     10.1. Disposition-Notification-Options header parameter names. 26
     10.2. Disposition modifier names . . . . . . . . . . . . . . . 26
     10.3. MDN extension field names. . . . . . . . . . . . . . . . 26
 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     12.1. Normative References . . . . . . . . . . . . . . . . . . 27
     12.2. Informative References . . . . . . . . . . . . . . . . . 28
 Appendix A - Changes from RFC 2298 . . . . . . . . . . . . . . . . 29
 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 30

Hansen & Vaudreuil Standards Track [Page 2] RFC 3798 Message Disposition Notification May 2004

1. Introduction

 This memo defines a [RFC-MIME-MEDIA] content-type for message
 disposition notifications (MDNs).  An MDN can be used to notify the
 sender of a message of any of several conditions that may occur after
 successful delivery, such as display of the message contents,
 printing of the message, deletion (without display) of the message,
 or the recipient's refusal to provide MDNs.  The
 "message/disposition-notification" content-type defined herein is
 intended for use within the framework of the "multipart/report"
 content type defined in [RFC-REPORT].
 This memo defines the format of the notifications and the [RFC-
 MSGFMT] headers used to request them.

1.1. Purposes

 The MDNs defined in this memo are expected to serve several purposes:
 (a)  Inform human beings of the disposition of messages after
      successful delivery, in a manner that is largely independent of
      human language;
 (b)  Allow mail user agents to keep track of the disposition of
      messages sent, by associating returned MDNs with earlier message
      transmissions;
 (c)  Convey disposition notification requests and disposition
      notifications between Internet Mail and "foreign" mail systems
      via a gateway;
 (d)  Allow "foreign" notifications to be tunneled through a MIME-
      capable message system and back into the original messaging
      system that issued the original notification, or even to a third
      messaging system;
 (e)  Allow language-independent, yet reasonably precise, indications
      of the disposition of a message to be delivered.

1.2. Requirements

 These purposes place the following constraints on the notification
 protocol:
 (a)  It must be readable by humans, and must be machine-parsable.

Hansen & Vaudreuil Standards Track [Page 3] RFC 3798 Message Disposition Notification May 2004

 (b)  It must provide enough information to allow message senders (or
      their user agents) to unambiguously associate an MDN with the
      message that was sent and the original recipient address for
      which the MDN was issued (if such information is available),
      even if the message was forwarded to another recipient address.
 (c)  It must also be able to describe the disposition of a message
      independent of any particular human language or of the
      terminology of any particular mail system.
 (d)  The specification must be extensible in order to accommodate
      future requirements.

1.3. Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC-KEYWORDS].
 All syntax descriptions use the ABNF specified by [RFC-MSGFMT], in
 which the lexical tokens (used below) are defined: "atom", "CRLF",
 "mailbox", "msg-id", and "text".  The following lexical tokens are
 defined in the definition of the Content-Type header in [RFC-MIME-
 BODY]: "attribute" and "value".

2. Requesting Message Disposition Notifications

 Message disposition notifications are requested by including a
 Disposition-Notification-To header in the message.  Further
 information to be used by the recipient's MUA in generating the MDN
 may be provided by also including Original-Recipient and/or
 Disposition-Notification-Options headers in the message.

2.1. The Disposition-Notification-To Header

 A request for the receiving user agent to issue message disposition
 notifications is made by placing a Disposition-Notification-To header
 into the message.  The syntax of the header is
 mdn-request-header = "Disposition-Notification-To" ":"
           mailbox *("," mailbox)
 The presence of a Disposition-Notification-To header in a message is
 merely a request for an MDN.  The recipients' user agents are always
 free to silently ignore such a request.  Alternatively, an explicit
 denial of the request for information about the disposition of the
 message may be sent using the "denied" disposition in an MDN.

Hansen & Vaudreuil Standards Track [Page 4] RFC 3798 Message Disposition Notification May 2004

 An MDN MUST NOT itself have a Disposition-Notification-To header.  An
 MDN MUST NOT be generated in response to an MDN.
 A user agent MUST NOT issue more than one MDN on behalf of each
 particular recipient.  That is, once an MDN has been issued on behalf
 of a recipient, no further MDNs may be issued on behalf of that
 recipient, even if another disposition is performed on the message.
 However, if a message is forwarded, an MDN may have been issued for
 the recipient doing the forwarding and the recipient of the forwarded
 message may also cause an MDN to be generated.
 While Internet standards normally do not specify the behavior of user
 interfaces, it is strongly recommended that the user agent obtain the
 user's consent before sending an MDN.  This consent could be obtained
 for each message through some sort of prompt or dialog box, or
 globally through the user's setting of a preference.  The user might
 also indicate globally that MDNs are to never be sent or that a
 "denied" MDN is always sent in response to a request for an MDN.
 MDNs SHOULD NOT be sent automatically if the address in the
 Disposition-Notification-To header differs from the address in the
 Return-Path header (see [RFC-MSGFMT]).  In this case, confirmation
 from the user SHOULD be obtained, if possible.  If obtaining consent
 is not possible (e.g., because the user is not online at the time),
 then an MDN SHOULD NOT be sent.
 Confirmation from the user SHOULD be obtained (or no MDN sent) if
 there is no Return-Path header in the message, or if there is more
 than one distinct address in the Disposition-Notification-To header.
 The comparison of the addresses should be done using only the addr-
 spec (local-part "@" domain) portion, excluding any phrase and route.
 The comparison MUST be case-sensitive for the local-part and case-
 insensitive for the domain part.
 If the message contains more than one Return-Path header, the
 implementation may pick one to use for the comparison, or treat the
 situation as a failure of the comparison.
 The reason for not automatically sending an MDN if the comparison
 fails or more than one address is specified is to reduce the
 possibility of mail loops and of MDNs being used for mail bombing.
 A message that contains a Disposition-Notification-To header SHOULD
 also contain a Message-ID header as specified in [RFC-MSGFMT].  This
 will permit automatic correlation of MDNs with their original
 messages by user agents.

Hansen & Vaudreuil Standards Track [Page 5] RFC 3798 Message Disposition Notification May 2004

 If the request for message disposition notifications for some
 recipients and not others is desired, two copies of the message
 should be sent, one with a Disposition-Notification-To header and one
 without.  Many of the other headers of the message (e.g., To, Cc)
 will be the same in both copies.  The recipients in the respective
 message envelopes determine for whom message disposition
 notifications are requested and for whom they are not.  If desired,
 the Message-ID header may be the same in both copies of the message.
 Note that there are other situations (e.g., Bcc) in which it is
 necessary to send multiple copies of a message with slightly
 different headers.  The combination of such situations and the need
 to request MDNs for a subset of all recipients may result in more
 than two copies of a message being sent, some with a Disposition-
 Notification-To header and some without.
 Messages posted to newsgroups SHOULD NOT have a Disposition-
 Notification-To header.

2.2. The Disposition-Notification-Options Header

 Future extensions to this specification may require that information
 be supplied to the recipient's MUA for additional control over how
 and what MDNs are generated.  The Disposition-Notification-Options
 header provides an extensible mechanism for such information.  The
 syntax of this header is as follows:
 Disposition-Notification-Options =
           "Disposition-Notification-Options" ":"
                          disposition-notification-parameters
 disposition-notification-parameters = parameter *(";" parameter)
 parameter = attribute "=" importance "," value *("," value)
 importance = "required" / "optional"
 An importance of "required" indicates that interpretation of the
 parameter is necessary for proper generation of an MDN in response to
 this request.  If an MUA does not understand the meaning of the
 parameter, it MUST NOT generate an MDN with any disposition type
 other than "failed" in response to the request.  An importance of
 "optional" indicates that an MUA that does not understand the meaning
 of this parameter MAY generate an MDN in response anyway, ignoring
 the value of the parameter.
 No parameters are defined in this specification.  Parameters may be
 defined in the future by later revisions or extensions to this
 specification.  Parameter attribute names beginning with "X-" will

Hansen & Vaudreuil Standards Track [Page 6] RFC 3798 Message Disposition Notification May 2004

 never be defined as standard names; such names are reserved for
 experimental use.  MDN parameter 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.)
 If a required parameter is not understood or contains some sort of
 error, the receiving MUA SHOULD issue an MDN with a disposition type
 of "failed" (see Section 3.2.6), and include a Failure field (see
 Section 3.2.7) that further describes the problem.  MDNs with the
 disposition type of "failed" and a "Failure" field MAY also be
 generated when other types of errors are detected in the parameters
 of the Disposition-Notification-Options header.
 However, an MDN with a disposition type of "failed" MUST NOT be
 generated if the user has indicated a preference that MDNs are not to
 be sent.  If user consent would be required for an MDN of some other
 disposition type to be sent, user consent SHOULD also be obtained
 before sending an MDN with a disposition type of "failed".

2.3. The Original-Recipient Header

 Since electronic mail addresses may be rewritten while the message is
 in transit, it is useful for the original recipient address to be
 made available by the delivering MTA.  The delivering MTA may be able
 to obtain this information from the ORCPT parameter of the SMTP RCPT
 TO command, as defined in [RFC-SMTP] and [RFC-DSN-SMTP].
 [RFC-DSN-SMTP] is amended as follows: If the ORCPT information is
 available, the delivering MTA SHOULD insert an Original-Recipient
 header at the beginning of the message (along with the Return-Path
 header).  The delivering MTA MAY delete any other Original-Recipient
 headers that occur in the message.  The syntax of this header is as
 follows:
 original-recipient-header =
             "Original-Recipient" ":" address-type ";" generic-address
 The address-type and generic-address token are as specified in the
 description of the Original-Recipient field in section 3.2.3.
 The purpose of carrying the original recipient information and
 returning it in the MDN is to permit automatic correlation of MDNs
 with the original message on a per-recipient basis.

Hansen & Vaudreuil Standards Track [Page 7] RFC 3798 Message Disposition Notification May 2004

2.4. Use with the Message/Partial Content Type

 The use of the headers Disposition-Notification-To, Disposition-
 Notification-Options, and Original-Recipient with the MIME
 message/partial content type ([RFC-MIME-MEDIA]) requires further
 definition.
 When a message is segmented into two or more message/partial
 fragments, the three headers mentioned in the above paragraph SHOULD
 be placed in the "inner" or "enclosed" message (using the terms of
 [RFC-MIME-MEDIA]).  These headers SHOULD NOT be used in the headers
 of any of the fragments themselves.
 When the multiple message/partial fragments are reassembled, the
 following applies.  If these headers occur along with the other
 headers of a message/partial fragment message, they pertain to an MDN
 that will be generated for the fragment.  If these headers occur in
 the headers of the "inner" or "enclosed" message (using the terms of
 [RFC-MIME-MEDIA]), they pertain to an MDN that will be generated for
 the reassembled message.  Section 5.2.2.1 of [RFC-MIME-MEDIA]) is
 amended to specify that, in addition to the headers specified there,
 the three headers described in this specification are to be appended,
 in order, to the headers of the reassembled message.  Any occurrences
 of the three headers defined here in the headers of the initial
 enclosing message must not be copied to the reassembled message.

3. Format of a Message Disposition Notification

 A message disposition notification is a MIME message with a top-level
 content-type of multipart/report (defined in [RFC-REPORT]).  When
 multipart/report content is used to transmit an MDN:
 (a)  The report-type parameter of the multipart/report content is
      "disposition-notification".
 (b)  The first component of the multipart/report contains a human-
      readable explanation of the MDN, as described in [RFC-REPORT].
 (c)  The second component of the multipart/report is of content-type
      message/disposition-notification, described in section 3.1 of
      this document.
 (d)  If the original message or a portion of the message is to be
      returned to the sender, it appears as the third component of the
      multipart/report.  The decision of whether or not to return the
      message or part of the message is up to the MUA generating the

Hansen & Vaudreuil Standards Track [Page 8] RFC 3798 Message Disposition Notification May 2004

      MDN.  However, in the case of encrypted messages requesting
      MDNs, encrypted message text MUST be returned, if it is returned
      at all, only in its original encrypted form.
  NOTE:  For message disposition notifications gatewayed from foreign
  systems, the headers of the original message may not be available.
  In this case, the third component of the MDN may be omitted, or it
  may contain "simulated" [RFC-MSGFMT] headers that contain equivalent
  information.  In particular, it is very desirable to preserve the
  subject and date fields from the original message.
 The MDN MUST be addressed (in both the message header and the
 transport envelope) to the address(es) from the Disposition-
 Notification-To header from the original message for which the MDN is
 being generated.
 The From field of the message header of the MDN MUST contain the
 address of the person for whom the message disposition notification
 is being issued.
 The envelope sender address (i.e., SMTP MAIL FROM) of the MDN MUST be
 null (<>), specifying that no Delivery Status Notification messages
 or other messages indicating successful or unsuccessful delivery are
 to be sent in response to an MDN.
 A message disposition notification MUST NOT itself request an MDN.
 That is, it MUST NOT contain a Disposition-Notification-To header.
 The Message-ID header (if present) for an MDN MUST be different from
 the Message-ID of the message for which the MDN is being issued.
 A particular MDN describes the disposition of exactly one message for
 exactly one recipient.  Multiple MDNs may be generated as a result of
 one message submission, one per recipient.  However, due to the
 circumstances described in Section 2.1, MDNs may not be generated for
 some recipients for which MDNs were requested.

3.1. The message/disposition-notification content-type

 The message/disposition-notification content-type is defined as
 follows:
 MIME type name:      message
 MIME subtype name:   disposition-notification
 Optional parameters: none

Hansen & Vaudreuil Standards Track [Page 9] RFC 3798 Message Disposition Notification May 2004

 Encoding considerations:  "7bit" encoding is sufficient and
                           MUST be used to maintain readability
                           when viewed by non-MIME mail readers.
 Security considerations:  discussed in section 6 of this memo.
 The message/disposition-notification report type for use in the
 multipart/report is "disposition-notification".
 The body of a message/disposition-notification consists of one or
 more "fields" formatted according to the ABNF of [RFC-MSGFMT] header
 "fields".  The syntax of the message/disposition-notification content
 is as follows:
 disposition-notification-content = [ reporting-ua-field CRLF ]
    [ mdn-gateway-field CRLF ]
    [ original-recipient-field CRLF ]
    final-recipient-field CRLF
    [ original-message-id-field CRLF ]
    disposition-field CRLF
    *( failure-field CRLF )
    *( error-field CRLF )
    *( warning-field CRLF )
    *( extension-field CRLF )

3.1.1. General conventions for fields

 Since these fields are defined according to the rules of [RFC-
 MSGFMT], the same conventions for continuation lines and comments
 apply. Notification fields may be continued onto multiple lines by
 beginning each additional line with a SPACE or HTAB.  Text that
 appears in parentheses is considered a comment and not part of the
 contents of that notification field.  Field names are case-
 insensitive, so the names of notification fields may be spelled in
 any combination of upper and lower case letters.  Comments in
 notification fields may use the "encoded-word" construct defined in
 [RFC-MIME-HEADER].

3.1.2. "*-type" subfields

 Several fields consist of a "-type" subfield, followed by a semi-
 colon, followed by "*text".  For these fields, the keyword used in
 the address-type or MTA-type subfield indicates the expected format
 of the address or MTA-name that follows.

Hansen & Vaudreuil Standards Track [Page 10] RFC 3798 Message Disposition Notification May 2004

 The "-type" subfields are defined as follows:
 (a)  An "address-type" specifies the format of a mailbox address.
      For example, Internet Mail addresses use the "rfc822" address-
      type.
      address-type = atom
 (b)  An "MTA-name-type" specifies the format of a mail transfer agent
      name.  For example, for an SMTP server on an Internet host, the
      MTA name is the domain name of that host, and the "dns" MTA-
      name-type is used.
      mta-name-type = atom
 Values for address-type and mta-name-type are case-insensitive.
 Thus, address-type values of "RFC822" and "rfc822" are equivalent.
 The Internet Assigned Numbers Authority (IANA) maintains a registry
 of address-type and mta-name-type values, along with descriptions of
 the meanings of each, or a reference to one or more specifications
 that provide such descriptions.  (The "rfc822" address-type is
 defined in [RFC-DSN-SMTP].)  Registration forms for address-type and
 mta-name-type appear in [RFC-DSN-FORMAT].

3.2. Message/disposition-notification Fields

3.2.1. The Reporting-UA field

  reporting-ua-field = "Reporting-UA" ":" ua-name
            [ ";" ua-product ]
  ua-name = *text
  ua-product = *text
 The Reporting-UA field is defined as follows:
 An MDN describes the disposition of a message after it has been
 delivered to a recipient.  In all cases, the Reporting-UA is the MUA
 that performed the disposition described in the MDN.  This field is
 optional, but recommended.  For Internet Mail user agents, it is
 recommended that this field contain both: the DNS name of the
 particular instance of the MUA that generated the MDN, and the name
 of the product.  For example,
  Reporting-UA:  pc.example.com; Foomail 97.1

Hansen & Vaudreuil Standards Track [Page 11] RFC 3798 Message Disposition Notification May 2004

 If the reporting MUA consists of more than one component (e.g., a
 base program and plug-ins), this may be indicated by including a list
 of product names.

3.2.2. The MDN-Gateway field

 The MDN-Gateway field indicates the name of the gateway or MTA that
 translated a foreign (non-Internet) message disposition notification
 into this MDN.  This field MUST appear in any MDN that was translated
 by a gateway from a foreign system into MDN format, and MUST NOT
 appear otherwise.
  mdn-gateway-field = "MDN-Gateway" ":" mta-name-type ";" mta-name
  mta-name = *text
 For gateways into Internet Mail, the MTA-name-type will normally be
 "smtp", and the mta-name will be the Internet domain name of the
 gateway.

3.2.3. Original-Recipient field

 The Original-Recipient field indicates the original recipient address
 as specified by the sender of the message for which the MDN is being
 issued.  For Internet Mail messages, the value of the Original-
 Recipient field is obtained from the Original-Recipient header from
 the message for which the MDN is being generated.  If there is no
 Original-Recipient header in the message, then the Original-Recipient
 field MUST be omitted, unless the same information is reliably
 available some other way.  If there is an Original-Recipient header
 in the original message (or original recipient information is
 reliably available some other way), then the Original-Recipient field
 must be supplied.  If there is more than one Original-Recipient
 header in the message, the MUA may choose the one to use, or act as
 if no Original-Recipient header is present.
  original-recipient-field =
            "Original-Recipient" ":" address-type ";"
            generic-address
  generic-address = *text
 The address-type field indicates the type of the original recipient
 address.  If the message originated within the Internet, the
 address-type field will normally be "rfc822", and the address will be
 according to the syntax specified in [RFC-MSGFMT].  The value
 "unknown" should be used if the Reporting MUA cannot determine the
 type of the original recipient address from the message envelope.

Hansen & Vaudreuil Standards Track [Page 12] RFC 3798 Message Disposition Notification May 2004

 This address is the same as that provided by the sender and can be
 used to automatically correlate MDN reports with original messages on
 a per recipient basis.

3.2.4. Final-Recipient field

 The Final-Recipient field indicates the recipient for which the MDN
 is being issued.  This field MUST be present.
 The syntax of the field is as follows:
  final-recipient-field =
            "Final-Recipient" ":" address-type ";" generic-address
 The generic-address subfield of the Final-Recipient field MUST
 contain the mailbox address of the recipient (from the From header of
 the MDN) as it was when the MDN was generated by the MUA.
 The Final-Recipient address may differ from the address originally
 provided by the sender, because it may have been transformed during
 forwarding and gatewaying into a totally unrecognizable mess.
 However, in the absence of the optional Original-Recipient field, the
 Final-Recipient field and any returned content may be the only
 information available with which to correlate the MDN with a
 particular message recipient.
 The address-type subfield indicates the type of address expected by
 the reporting MTA in that context.  Recipient addresses obtained via
 SMTP will normally be of address-type "rfc822".
 Since mailbox addresses (including those used in the Internet) may be
 case sensitive, the case of alphabetic characters in the address MUST
 be preserved.

3.2.5. Original-Message-ID field

 The Original-Message-ID field indicates the message-ID of the message
 for which the MDN is being issued.  It is obtained from the Message-
 ID header of the message for which the MDN is issued.  This field
 MUST be present if the original message contained a Message-ID
 header.  The syntax of the field is as follows:
  original-message-id-field =
     "Original-Message-ID" ":" msg-id
 The msg-id token is as specified in [RFC-MSGFMT].

Hansen & Vaudreuil Standards Track [Page 13] RFC 3798 Message Disposition Notification May 2004

3.2.6. Disposition field

 The Disposition field indicates the action performed by the
 Reporting-MUA on behalf of the user.  This field MUST be present.
 The syntax for the Disposition field is:
  disposition-field =
            "Disposition" ":" disposition-mode ";"
            disposition-type
            [ "/" disposition-modifier
            *( "," disposition-modifier ) ]
  disposition-mode = action-mode "/" sending-mode
  action-mode = "manual-action" / "automatic-action"
  sending-mode = "MDN-sent-manually" / "MDN-sent-automatically"
  disposition-type = "displayed"
             / "deleted"
  disposition-modifier = "error"
            / disposition-modifier-extension
  disposition-modifier-extension = atom
 The disposition-mode, disposition-type, and disposition-modifier may
 be spelled in any combination of upper and lower case characters.

3.2.6.1. Disposition modes

 The following disposition modes are defined:
  "manual-action"        The disposition described by the disposition
                         type was a result of an explicit instruction
                         by the user rather than some sort of
                         automatically performed action.
  "automatic-action"     The disposition described by the disposition
                         type was a result of an automatic action,
                         rather than an explicit instruction by the
                         user for this message.
 "Manual-action" and "automatic-action" are mutually exclusive.  One
 or the other MUST be specified.

Hansen & Vaudreuil Standards Track [Page 14] RFC 3798 Message Disposition Notification May 2004

  "MDN-sent-manually"    The user explicitly gave permission for this
                         particular MDN to be sent.
  "MDN-sent-automatically"
                         The MDN was sent because the MUA had
                         previously been configured to do so
                         automatically.
 "MDN-sent-manually" and "MDN-sent-automatically" are mutually
 exclusive.  One or the other MUST be specified.

3.2.6.2. Disposition types

 The following disposition-types are defined:
  "displayed"            The message has been displayed by the MUA
                         to someone reading the recipient's mailbox.
                         There is no guarantee that the content has
                         been read or understood.
  "deleted"              The message has been deleted.  The
                         recipient may or may not have seen the
                         message.  The recipient might "undelete"
                         the message at a later time and read the
                         message.

3.2.6.3. Disposition modifiers

 Only the extension disposition modifiers is defined:
  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

Hansen & Vaudreuil Standards Track [Page 15] RFC 3798 Message Disposition Notification May 2004

                         user's mailbox without special
                         interpretation.  They MUST not cause any
                         error message to be sent to the sender of
                         the MDN.
 If an MUA developer does not wish to register the meanings of such
 disposition modifier extensions, "X-" modifiers may be used for this
 purpose.  To avoid name collisions, the name of the MUA
 implementation should follow the "X-", (e.g., "X-Foomail-").
 It is not required that an MUA be able to generate all of the
 possible values of the Disposition field.
 A user agent MUST NOT issue more than one MDN on behalf of each
 particular recipient.  That is, once an MDN has been issued on behalf
 of a recipient, no further MDNs may be issued on behalf of that
 recipient, even if another disposition is performed on the message.
 However, if a message is forwarded, a "dispatched" MDN may be issued
 for the recipient doing the forwarding and the recipient of the
 forwarded message may also cause an MDN to be generated.

3.2.7. Failure, Error, and Warning fields

 The Failure, Error, and Warning fields are used to supply additional
 information in the form of text messages when the "failure"
 disposition type, "error" disposition modifier, and/or the "warning"
 disposition modifier appear.  The syntax is as follows:
    failure-field = "Failure" ":" *text
    error-field = "Error" ":" *text
    warning-field = "Warning" ":" *text

3.3. Extension-fields

 Additional MDN fields may be defined in the future by later revisions
 or extensions to this specification.  Extension-field names beginning
 with "X-" will never be defined as standard fields; such names are
 reserved for experimental use.  MDN field 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.)

Hansen & Vaudreuil Standards Track [Page 16] RFC 3798 Message Disposition Notification May 2004

 MDN Extension-fields may be defined for the following reasons:
 (a)  To allow additional information from foreign disposition reports
      to be tunneled through Internet MDNs.  The names of such MDN
      fields should begin with an indication of the foreign
      environment name (e.g., X400-Physical-Forwarding-Address).
 (b)  To allow transmission of diagnostic information that is specific
      to a particular mail user agent (MUA).  The names of such MDN
      fields should begin with an indication of the MUA implementation
      that produced the MDN (e.g., Foomail-information).
 If an application developer does not wish to register the meanings of
 such extension fields, "X-" fields may be used for this purpose.  To
 avoid name collisions, the name of the application implementation
 should follow the "X-", (e.g., "X-Foomail-Log-ID" or "X-Foomail-EDI-
 info").

4. Timeline of events

 The following timeline shows when various events in the processing of
 a message and generation of MDNs take place:
  1. - User composes message
  1. - User tells MUA to send message
  1. - MUA passes message to MTA (original recipient information passed

along)

  1. - MTA sends message to next MTA
  1. - Final MTA receives message
  1. - Final MTA delivers message to MUA (possibly generating a DSN)
  1. - MUA performs automatic processing and generates corresponding MDNs

("dispatched", "processed", "deleted", "denied", or "failed"

    disposition type with "automatic-action" and "MDN-sent-
    automatically" disposition modes)
  1. - MUA displays list of messages to user
  1. - User selects a message and requests that some action be performed

on it.

Hansen & Vaudreuil Standards Track [Page 17] RFC 3798 Message Disposition Notification May 2004

  1. - MUA performs requested action and, with user's permission, sends

an appropriate MDN ("displayed", "dispatched", "processed",

    "deleted", "denied", or "failed" disposition type, with "manual-
    action" and "MDN-sent-manually" or "MDN-sent-automatically"
    disposition mode).
  1. - User possibly performs other actions on message, but no further

MDNs are generated.

5. Conformance and Usage Requirements

 An MUA or gateway conforms to this specification if it generates MDNs
 according to the protocol defined in this memo.  It is not necessary
 to be able to generate all of the possible values of the Disposition
 field.
 MUAs and gateways MUST NOT generate the Original-Recipient field of
 an MDN unless the mail protocols provide the address originally
 specified by the sender at the time of submission.  Ordinary SMTP
 does not make that guarantee, but the SMTP extension defined in
 [RFC-DSN-SMTP] permits such information to be carried in the envelope
 if it is available.  The Original-Recipient header defined in this
 document provides a way for the MTA to pass the original recipient
 address to the MUA.
 Each sender-specified recipient address may result in more than one
 MDN.  If an MDN is requested for a recipient that is forwarded to
 multiple recipients of an "alias" (as defined in [RFC-DSN-SMTP],
 section 6.2.7.3), each of the recipients may issue an MDN.
 Successful distribution of a message to a mailing list exploder
 SHOULD be considered the final disposition of the message.  A mailing
 list exploder MAY issue an MDN with a disposition type of "processed"
 and disposition modes of "automatic-action" and "MDN-sent-
 automatically" indicating that the message has been forwarded to the
 list.  In this case, the request for MDNs is not propagated to the
 members of the list.
 Alternatively, the mailing list exploder MAY issue no MDN and
 propagate the request for MDNs to all members of the list.  The
 latter behavior is not recommended for any but small, closely knit
 lists, as it might cause large numbers of MDNs to be generated and
 may cause confidential subscribers to the list to be revealed.  The
 mailing list exploder MAY also direct MDNs to itself, correlate them,
 and produce a report to the original sender of the message.
 This specification places no restrictions on the processing of MDNs
 received by user agents or mailing lists.

Hansen & Vaudreuil Standards Track [Page 18] RFC 3798 Message Disposition Notification May 2004

6. Security Considerations

 The following security considerations apply when using MDNs:

6.1. Forgery

 MDNs may be forged as easily as ordinary Internet electronic mail.
 User agents and automatic mail handling facilities (such as mail
 distribution list exploders) that wish to make automatic use of MDNs
 should take appropriate precautions to minimize the potential damage
 from denial-of-service attacks.
 Security threats related to forged MDNs include the sending of:
 (a)  A falsified disposition notification when the indicated
      disposition of the message has not actually occurred,
 (b)  Unsolicited MDNs

6.2. Privacy

 Another dimension of security is privacy.  There may be cases in
 which a message recipient does not wish the disposition of messages
 addressed to him to be known, or is concerned that the sending of
 MDNs may reveal other sensitive information (e.g., when the message
 was read).  In this situation, it is acceptable for the MUA to issue
 "denied" MDNs or to silently ignore requests for MDNs.
 If the Disposition-Notification-To header is passed on unmodified
 when a message is distributed to the subscribers of a mailing list,
 the subscribers to the list may be revealed to the sender of the
 original message by the generation of MDNs.
 Headers of the original message returned in part 3 of the
 multipart/report could reveal confidential information about host
 names and/or network topology inside a firewall.
 An unencrypted MDN could reveal confidential information about an
 encrypted message, especially if all or part of the original message
 is returned in part 3 of the multipart/report.  Encrypted MDNs are
 not defined in this specification.
 In general, any optional MDN field may be omitted if the Reporting
 MUA site or user determines that inclusion of the field would impose
 too great a compromise of site confidentiality.  The need for such
 confidentiality must be balanced against the utility of the omitted
 information in MDNs.

Hansen & Vaudreuil Standards Track [Page 19] RFC 3798 Message Disposition Notification May 2004

 In some cases, someone with access to the message stream may use the
 MDN request mechanism to monitor the mail reading habits of a target.
 If the target is known to generate MDN reports, they could add a
 disposition-notification-to field containing the envelope from
 address along with a source route.  The source route is ignored in
 the comparison so the addresses will always match.  But if the source
 route is honored when the notification is sent, it could direct the
 message to some other destination.  This risk can be minimized by not
 sending MDN's automatically.

6.3. Non-Repudiation

 MDNs do not provide non-repudiation with proof of delivery.  Within
 the framework of today's Internet Mail, the MDNs defined in this
 document provide valuable information to the mail user; however, MDNs
 cannot be relied upon as a guarantee that a message was or was not
 seen by the recipient.  Even if MDNs are not actively forged, they
 may be lost in transit.  The recipient may bypass the MDN issuing
 mechanism in some manner.
 One possible solution for this purpose can be found in RFC 2634
 [SEC-SERVICES].

6.4. Mail Bombing

 The MDN request mechanism introduces an additional way of mailbombing
 a mailbox.  The MDN request notification provides an address to which
 MDN's should be sent.  It is possible for an attacking agent to send
 a potentially large set of messages to otherwise unsuspecting third
 party recipients with a false "disposition-notification-to:" address.
 Automatic, or simplistic processing of such requests would result in
 a flood of MDN notifications to the target of the attack.  Such an
 attack could overrun the capacity of the targeted mailbox and deny
 service.
 For that reason, MDN's SHOULD NOT be sent automatically where the
 "disposition-notification-to:" address is different from the envelope
 MAIL FROM address.  See section 2.1 for further discussion.

7. Collected Grammar

 NOTE:  The following lexical tokens are defined in [RFC-MSGFMT]:
 atom, CRLF, mailbox, msg-id, text.  The definitions of attribute and
 value are as in the definition of the Content-Type header in [RFC-
 MIME-BODY].

Hansen & Vaudreuil Standards Track [Page 20] RFC 3798 Message Disposition Notification May 2004

Message headers:

mdn-request-header =
   "Disposition-Notification-To" ":"
          mailbox *("," mailbox)
Disposition-Notification-Options =
          "Disposition-Notification-Options" ":"
          disposition-notification-parameters
disposition-notification-parameters =
          parameter *(";" parameter)
parameter = attribute "=" importance "," value *("," value)
importance = "required" / "optional"
original-recipient-header =
          "Original-Recipient" ":" address-type ";" generic-address

Report content:

disposition-notification-content =
          [ reporting-ua-field CRLF ]
          [ mdn-gateway-field CRLF ]
          [ original-recipient-field CRLF ]
          final-recipient-field CRLF
          [ original-message-id-field CRLF ]
          disposition-field CRLF
          *( failure-field CRLF )
          *( error-field CRLF )
          *( warning-field CRLF )
          *( extension-field CRLF )
address-type = atom
mta-name-type = atom
reporting-ua-field = "Reporting-UA" ":" ua-name [ ";" ua-product ]
ua-name = *text
ua-product = *text
mdn-gateway-field = "MDN-Gateway" ":" mta-name-type ";" mta-name
mta-name = *text

Hansen & Vaudreuil Standards Track [Page 21] RFC 3798 Message Disposition Notification May 2004

original-recipient-field
          = "Original-Recipient" ":" address-type ";"
          generic-address
generic-address = *text
final-recipient-field =
          "Final-Recipient" ":" address-type ";" generic-address
disposition-field =
          "Disposition" ":" disposition-mode ";"
          disposition-type
          [ "/" disposition-modifier
          *( "," disposition-modifier ) ]
disposition-mode = action-mode "/" sending-mode
action-mode = "manual-action" / "automatic-action"
sending-mode = "MDN-sent-manually" / "MDN-sent-automatically"
disposition-type = "displayed"
          / "deleted"
disposition-modifier =  "error" / disposition-modifier-extension
disposition-modifier-extension = atom
original-message-id-field = "Original-Message-ID" ":" msg-id
failure-field = "Failure" ":" *text
error-field = "Error" ":" *text
warning-field = "Warning" ":" *text
extension-field = extension-field-name ":" *text
extension-field-name = atom

8. Guidelines for Gatewaying MDNs

 NOTE:  This section provides non-binding recommendations for the
 construction of mail gateways that wish to provide semi-transparent
 disposition notifications between the Internet and another electronic
 mail system.  Specific MDN gateway requirements for a particular pair
 of mail systems may be defined by other documents.

Hansen & Vaudreuil Standards Track [Page 22] RFC 3798 Message Disposition Notification May 2004

8.1. Gatewaying from other mail systems to MDNs

 A mail gateway may issue an MDN to convey the contents of a "foreign"
 disposition notification over Internet Mail.  When there are
 appropriate mappings from the foreign notification elements to MDN
 fields, the information may be transmitted in those MDN fields.
 Additional information (such as might be needed to tunnel the foreign
 notification through the Internet) may be defined in extension MDN
 fields.  (Such fields should be given names that identify the foreign
 mail protocol, e.g., X400-* for X.400 protocol elements).
 The gateway must attempt to supply reasonable values for the
 Reporting-UA, Final-Recipient, and Disposition fields.  These will
 normally be obtained by translating the values from the foreign
 notification into their Internet-style equivalents.  However, some
 loss of information is to be expected.
 The sender-specified recipient address and the original message-id,
 if present in the foreign notification, should be preserved in the
 Original-Recipient and Original-Message-ID fields.
 The gateway should also attempt to preserve the "final" recipient
 address from the foreign system.  Whenever possible, foreign protocol
 elements should be encoded as meaningful printable ASCII strings.
 For MDNs produced from foreign disposition notifications, the name of
 the gateway MUST appear in the MDN-Gateway field of the MDN.

8.2. Gatewaying from MDNs to other mail systems

 It may be possible to gateway MDNs from the Internet into a foreign
 mail system.  The primary purpose of such gatewaying is to convey
 disposition information in a form that is usable by the destination
 system.  A secondary purpose is to allow "tunneling" of MDNs through
 foreign mail systems in case the MDN may be gatewayed back into the
 Internet.
 In general, the recipient of the MDN (i.e., the sender of the
 original message) will want to know, for each recipient:  the closest
 available approximation to the original recipient address, and the
 disposition (displayed, printed, etc.).
 If possible, the gateway should attempt to preserve the Original-
 Recipient address and Original-Message-ID (if present) in the
 resulting foreign disposition report.

Hansen & Vaudreuil Standards Track [Page 23] RFC 3798 Message Disposition Notification May 2004

 If it is possible to tunnel an MDN through the destination
 environment, the gateway specification may define a means of
 preserving the MDN information in the disposition reports used by
 that environment.

8.3. Gatewaying of MDN-requests to other mail systems

 By use of the separate disposition-notification-to request header,
 this specification offers a richer functionality than most, if not
 all, other email systems.  In most other email systems, the
 notification recipient is identical to the message sender as
 indicated in the "from" address.  There are two interesting cases
 when gatewaying into such systems:
 1) If the address in the disposition-notification-to header is
    identical to the address in the SMTP "MAIL FROM", the expected
    behavior will result, even if the disposition-notification-to
    information is lost.  Systems should propagate the MDN request.
 2) If the address in the disposition-notification-to header is
    different from the address in the SMTP "MAIL FROM", gatewaying
    into a foreign system without a separate notification address will
    result in unintended behavior.  This is especially important when
    the message arrives via a mailing list expansion software that may
    specifically replace the SMTP "MAIL FROM" address with an
    alternate address.  In such cases, the MDN request should not be
    gatewayed and should be silently dropped.  This is consistent with
    other forms of non-support for MDN.

9. Example

 NOTE:  This example is provided as illustration only, and is not
 considered part of the MDN protocol specification.  If the example
 conflicts with the protocol definition above, the example is wrong.
 Likewise, the use of *-type subfield names or extension fields in
 this example is not to be construed as a definition for those type
 names or extension fields.
 This is an MDN issued after a message has been displayed to the user
 of an Internet Mail user agent.
 Date: Wed, 20 Sep 1995 00:19:00 (EDT) -0400
 From: Joe Recipient <Joe_Recipient@example.com>
 Message-Id: <199509200019.12345@example.com>
 Subject: Disposition notification
 To: Jane Sender <Jane_Sender@example.org>
 MIME-Version: 1.0

Hansen & Vaudreuil Standards Track [Page 24] RFC 3798 Message Disposition Notification May 2004

 Content-Type: multipart/report; report-type=disposition-notification;
    boundary="RAA14128.773615765/example.com"
  1. -RAA14128.773615765/example.com
 The message sent on 1995 Sep 19 at 13:30:00 (EDT) -0400 to Joe
 Recipient <Joe_Recipient@example.com> with subject "First draft of
 report" has been displayed.  This is no guarantee that the message
 has been read or understood.
  1. -RAA14128.773615765/example.com

content-type: message/disposition-notification

 Reporting-UA: joes-pc.cs.example.com; Foomail 97.1
 Original-Recipient: rfc822;Joe_Recipient@example.com
 Final-Recipient: rfc822;Joe_Recipient@example.com
 Original-Message-ID: <199509192301.23456@example.org>
 Disposition: manual-action/MDN-sent-manually; displayed
  1. -RAA14128.773615765/example.com

content-type: message/rfc822

 [original message optionally goes here]
  1. -RAA14128.773615765/example.com–

10. IANA Considerations

 This document specifies three types of parameters that must be
 registered with the Internet Assigned Numbers Authority (IANA).
 The forms below are for use when registering a new parameter name for
 the Disposition-Notification-Options header, a new disposition
 modifier name, or a new MDN extension field.  Each piece of
 information required by a registration form may be satisfied either
 by providing the information on the form itself, or by including a
 reference to a published, publicly available specification that
 includes the necessary information.  IANA MAY reject registrations
 because of incomplete registration forms or incomplete
 specifications.
 To register, complete the following applicable form and send it via
 electronic mail to <IANA@IANA.ORG>.

Hansen & Vaudreuil Standards Track [Page 25] RFC 3798 Message Disposition Notification May 2004

10.1. Disposition-Notification-Options header parameter names

 A registration for a Disposition-Notification-Options header
 parameter name MUST include the following information:
 (a)  The proposed parameter name.
 (b)  The syntax for parameter values, specified using BNF, ABNF,
      regular expressions, or other non-ambiguous language.
 (c)  If parameter values are not composed entirely of graphic
      characters from the US-ASCII repertoire, a specification for how
      they are to be encoded as graphic US-ASCII characters in a
      Disposition-Notification-Options header.
 (d)  A reference to a standards track RFC or experimental RFC
      approved by the IESG that describes the semantics of the
      parameter values.

10.2. Disposition modifier names

 A registration for a disposition-modifier name (used in the
 Disposition field of a message/disposition-notification) MUST include
 the following information:
 (a)  The proposed disposition-modifier name.
 (b)  A reference to a standards track RFC or experimental RFC
      approved by the IESG that describes the semantics of the
      disposition modifier.

10.3. MDN extension field names

 A registration for an MDN extension-field name MUST include the
 following information:
 (a)  The proposed extension field name.
 (b)  The syntax for extension values, specified using BNF, ABNF,
      regular expressions, or other non-ambiguous language.
 (c)  If extension-field values are not composed entirely of graphic
      characters from the US-ASCII repertoire, a specification for how
      they are to be encoded as graphic US-ASCII characters in a
      Disposition-Notification-Options header.

Hansen & Vaudreuil Standards Track [Page 26] RFC 3798 Message Disposition Notification May 2004

 (d)  A reference to a standards track RFC or experimental RFC
      approved by the IESG that describes the semantics of the
      extension field.

11. Acknowledgments

 This document is an updated version of the original document written
 by Roger Fajman.  His contributions to the definition of Message
 Disposition Notifications are greatly appreciated.
 RFC 2298 was based on the Delivery Status Notifications document
 [RFC-DSN-FORMAT] by Keith Moore and Greg Vaudreuil.  Contributions
 were made by members of the IETF Receipt Working Group, including
 Harald Alvestrand, Ian Bell, Urs Eppenberger, Claus Andri Faerber,
 Ned Freed, Jim Galvin, Carl Hage, Mike Lake, Keith Moore, Paul
 Overell, Pete Resnick, and Chuck Shih.

12. References

12.1. Normative References

 [RFC-SMTP]        Klensin, J., Ed., "Simple Mail Transfer Protocol",
                   RFC 2821, April 2001.
 [RFC-MSGFMT]      Resnick, P., Ed., "Internet Message Format", RFC
                   2822, April 2001.
 [RFC-MIME-BODY]   Freed, N. and N. Borenstein, "Multipurpose Internet
                   Mail Extensions (MIME) Part One: Format of Internet
                   Message Bodies", RFC 2045, November 1996.
 [RFC-MIME-MEDIA]  Freed, N. and N. Borenstein, "Multipurpose Internet
                   Mail Extensions (MIME) Part Two: Media Types", RFC
                   2046, November 1996.
 [RFC-MIME-HEADER] Moore, K., "MIME (Multipurpose Internet Mail
                   Extensions) Part Three: Message Header Extensions
                   for Non-ASCII Text", RFC 2047, November 1996.
 [RFC-REPORT]      Vaudreuil, G., "The Multipart/Report Content Type
                   for the Reporting of Mail System Administrative
                   Messages", RFC 3462, January 2003.
 [RFC-DSN-SMTP]    Moore, K., "Simple Mail Transfer Protocol (SMTP)
                   Service Extension for Delivery Status
                   Notifications", RFC 3461, January 2003.

Hansen & Vaudreuil Standards Track [Page 27] RFC 3798 Message Disposition Notification May 2004

 [RFC-DSN-FORMAT]  Moore, K., and G. Vaudreuil, "An Extensible Format
                   for Delivery Status Notifications (DSNs)", RFC
                   3464, January 2003.
 [RFC-KEYWORDS]    Bradner, S., "Key Words for Use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.

12.2. Informative References

 [SEC-SERVICES]    Hoffman, P., Ed., "Enhanced Security Services for
                   S/MIME", RFC 2634, June 1999.

Hansen & Vaudreuil Standards Track [Page 28] RFC 3798 Message Disposition Notification May 2004

Appendix A - Changes from RFC 2298

 The document has new editors.
 The dispositions "denied", and "failed" were removed from the
 document reflecting the lack of implementation or usage at this time.
 The disposition modifiers "warning", "superseded", "expired",
 "mailbox-terminated" have not seen actual implementation.  They have
 been deleted from this document.  The extension modifier, as of yet
 unused, has been retained for future extension.
 General editorial cleanups include spelling, grammar, and consistency
 in usage of terms.
 The document has modified BNF for disposition notification options to
 eliminate the need for dummy values where not otherwise needed.

Authors' Addresses

 Tony Hansen
 AT&T Laboratories
 Middletown, NJ 07748
 USA
 Voice: +1-732-420-8934
 EMail: tony+rfc3798@maillennium.att.com
 Gregory M. Vaudreuil
 Lucent Technologies
 7291 Williamson Rd
 Dallas, TX 75214
 USA
 Voice: +1 214 823 9325
 EMail: GregV@ieee.org

Hansen & Vaudreuil Standards Track [Page 29] RFC 3798 Message Disposition Notification May 2004

Full Copyright Statement

 Copyright (C) The Internet Society (2004).  This document is subject
 to the rights, licenses and restrictions contained in BCP 78, and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Hansen & Vaudreuil Standards Track [Page 30]

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