Tech-invite3GPPspaceIETF RFCsSIP
93929190898887868584838281807978777675747372717069686766656463626160595857565554535251504948474645444342414039383736353433323130292827262524232221201918171615141312111009080706050403020100
in Index   Prev   Next

RFC 3503

Message Disposition Notification (MDN) profile for Internet Message Access Protocol (IMAP)

Pages: 9
Proposed Standard

Top   ToC   RFC3503 - Page 1
Network Working Group                                        A. Melnikov
Request for Comments: 3503                 ACI Worldwide/MessagingDirect
Category: Standards Track                                     March 2003


          Message Disposition Notification (MDN) profile for
                Internet Message Access Protocol (IMAP)

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 (2003).  All Rights Reserved.

Abstract

The Message Disposition Notification (MDN) facility defined in RFC 2298 provides a means by which a message can request that message processing by the recipient be acknowledged as well as a format to be used for such acknowledgements. However, it doesn't describe how multiple Mail User Agents (MUAs) should handle the generation of MDNs in an Internet Message Access Protocol (IMAP4) environment. This document describes how to handle MDNs in such an environment and provides guidelines for implementers of IMAP4 that want to add MDN support to their products.
Top   ToC   RFC3503 - Page 2

Table of Contents

1. Conventions Used in this Document............................. 2 2. Introduction and Overview..................................... 2 3. Client behavior............................................... 3 3.1. Client behavior when receiving a message................. 5 3.2. Client behavior when copying a message................... 5 3.3. Client behavior when sending a message................... 5 3.4. Client behavior when saving a temporary message.......... 5 4. Server behavior............................................... 5 4.1. Server that supports arbitrary keywords.................. 5 4.2. Server that supports only $MDNSent keyword............... 5 4.3. Interaction with IMAP ACL extension...................... 6 5. Examples...................................................... 6 6. Security Considerations....................................... 7 7. Formal Syntax................................................. 7 8. Acknowledgments............................................... 7 9. Normative References.......................................... 8 10. Author's Address.............................................. 8 11. Full Copyright Statement...................................... 9

1. Conventions Used in this Document

"C:" and "S:" in examples show lines sent by the client and server respectively. The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in this document when typed in uppercase are to be interpreted as defined in "Key words for use in RFCs to Indicate Requirement Levels" [KEYWORDS].

2. Introduction and Overview

This memo defines an additional [IMAP4] mailbox keyword that allows multiple Mail User Agents (MUAs) to know if a requested receipt notification was sent. Message Disposition Notification [MDN] does not require any special support of IMAP in the case where a user has access to the mailstore from only one computer and is using a single MUA. In this case, the MUA behaves as described in [MDN], i.e., the MUA performs automatic processing and generates corresponding MDNs, it performs requested action and, with the user's permission, sends appropriate MDNs. The MUA will not send MDN twice because the MUA keeps track of sent notifications in a local configuration. However, that does not work when IMAP is used to access the same mailstore from different locations or is using different MUAs.
Top   ToC   RFC3503 - Page 3
   This document defines a new special purpose mailbox keyword $MDNSent
   that must be used by MUAs.  It does not define any new command or
   response for IMAP, but describes a technique that MUAs should use to
   achieve interoperability.

   When a client opens a mailbox for the first time, it verifies that
   the server is capable of storing the $MDNSent keyword by examining
   the PERMANENTFLAGS response code.  In order to support MDN in IMAP, a
   server MUST support either the $MDNSent keyword, or arbitrary message
   keywords.

3. Client behavior

The use of IMAP requires few additional steps in mail processing on the client side. The following timeline modifies the timeline found in Section 4 of [MDN]. -- User composes message. -- User tells MUA to send message. -- MUA passes message to MSA (original recipient information passed along). MUA [optionally] saves message to a folder for sent mail with $MDNSent flag set. -- MSA sends message to MTA. -- Final MTA receives message. -- Final MTA delivers message to MUA (possibly generating DSN). -- MUA logs into IMAP server, opens mailbox, verifies if mailbox can store $MDNSent keyword by examining PERMANENTFLAGS response. -- 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) for messages that do not have $MDNSent keyword, or \Draft flag set. (*) -- MUA sets the $MDNSent keyword for every message that required an automatic MDN to be sent, whether or not the MDN was sent. -- MUA displays a list of messages to user. -- User selects a message and requests that some action be performed on it.
Top   ToC   RFC3503 - Page 4
   -- MUA performs requested action and, with user's permission, sends
      appropriate MDN ("displayed", "dispatched", "processed",
      "deleted", "denied" or "failed" disposition type with "manual-
      action" and "MDN-sent-manually" or "MDN-sent-automatically"
      disposition mode).  If the generated MDN is saved to a mailbox
      with the APPEND command, the client MUST specify the $MDNSent
      keyword in the APPEND.

   -- MUA sets the $MDNSent keyword for all messages for which the user
      confirmed the dispatching of disposition (or was explicitly
      prohibited to do so).

   -- User possibly performs other actions on message, but no further
      MDNs are generated.

   (*) Note: MUA MUST NOT use \Recent flag as an indicator that it
       should send MDN, because according to [IMAP4], "If multiple
       connections have the same mailbox selected simultaneously, it is
       undefined which of these connections will see newly-arrived
       messages with \Recent set and which will see it without \Recent
       set".  Thus, using \Recent as an indicator will cause
       unpredictable client behavior with different IMAP4 servers.
       However, the client MAY use \Seen flag as one of the indicators
       that MDN must not be sent.  The client MUST NOT use any other
       standard flags, like \Draft or \Answered, to indicate that MDN
       was previously sent, because they have different well known
       meaning.  In any case, in the presence of the $MDNSent keyword,
       the client MUST ignore all other flags or keywords for the
       purpose of generating an MDN and MUST NOT send the MDN.

   When the client opens a mailbox for the first time, it must verify
   that the server supports the $MDNSent keyword, or arbitrary message
   keywords by examining PERMANENTFLAGS response code.

   The client MUST NOT try to set the $MDNSent keyword if the server is
   incapable of storing it permanently.

   The client MUST be prepared to receive NO from the server as the
   result of STORE $MDNSent when the server advertises the support of
   storing arbitrary keywords, because the server may limit the number
   of message keywords it can store in a particular mailbox.  A client
   SHOULD NOT send MDN if it fails to store the $MDNSent keyword.

   Once the $MDNSent keyword is set, it MUST NOT be unset by a client.
   The client MAY set the $MDNSent keyword when a user denies sending
   the notification.  This prohibits all other MUAs from sending MDN for
   this message.
Top   ToC   RFC3503 - Page 5

3.1. Client behavior when receiving a message

The client MUST NOT send MDN if a message has the $MDNSent keyword set. It also MUST NOT send MDN if a message has \Draft flag, because some clients use this flag to mark a message as incomplete. See the timeline in section 3 for details on client behavior when receiving a message.

3.2. Client behavior when copying a message

The client SHOULD verify that $MDNSent is preserved on a COPY operation. Furthermore, when a message is copied between servers with the APPEND command, the client MUST set the $MDNSent keyword correctly.

3.3. Client behavior when sending a message

When saving a sent message to any folder, the client MUST set the $MDNSent keyword to prevent another client from sending MDN for the message.

3.4. Client behavior when saving a temporary message

When saving an unfinished message to any folder client MUST set $MDNSent keyword to prevent another client from sending MDN for the message.

4. Server behavior

Server implementors that want to follow this specification must insure that their server complies with either section 4.1 or section 4.2. If the server also supports the IMAP [ACL] extension, it MUST also comply with the section 4.3.

4.1. Server that supports arbitrary keywords

No changes are required from the server to make it compatible with the extension described in this document if it supports arbitrary keywords.

4.2. Server that supports only $MDNSent keyword

Servers that support only the $MDNSent keyword MUST preserve it on the COPY operation. It is also expected that a server that supports SEARCH <flag> will also support the SEARCH KEYWORD $MDNSent.
Top   ToC   RFC3503 - Page 6

4.3. Interaction with IMAP ACL extension

Any server that conforms to either 4.1 or 4.2 and also supports the IMAP [ACL] extension, SHOULD preserve the $MDNSent keyword on COPY even if the client does not have 'w' right. This will prevent the generation of a duplicated MDN for the same message. Note that the server MUST still check if the client has rights to perform the COPY operation on a message according to [ACL].

5. Examples

1) MUA opens mailbox for the first time. a) The server supports storing of arbitrary keywords C: a100 select INBOX S: * FLAGS (\Flagged \Draft \Deleted \Seen) S: * OK [PERMANENTFLAGS (\Flagged \Draft \Deleted \Seen \*)] S: * 5 EXISTS S: * 3 RECENT S: * OK [UIDVALIDITY 894294713] S: a100 OK [READ-WRITE] Completed b) The server supports storing of the $MDNSent keyword C: a100 select INBOX S: * FLAGS (\Flagged \Draft \Deleted \Seen $MDNSent) S: * OK [PERMANENTFLAGS (\Flagged \Draft \Deleted \Seen $MDNSent)] S: * 5 EXISTS S: * 3 RECENT S: * OK [UIDVALIDITY 894294713] S: a100 OK [READ-WRITE] Completed 2) The MUA successfully sets the $MDNSent keyword C: a200 STORE 4 +FLAGS ($MDNSent) S: * 4 FETCH (FLAGS (\Flagged \Seen $MDNSent)) S: * FLAGS ($MDNSent \Flagged \Deleted \Draft \Seen) S: * OK [PERMANENTFLAGS ($MDNSent \Flagged \Deleted \Draft \Seen \*)] S: a200 OK STORE completed 3) The server refuses to store the $MDNSent keyword C: a200 STORE 4 +FLAGS ($MDNSent) S: a200 NO STORE failed : no space left to store $MDNSent keyword
Top   ToC   RFC3503 - Page 7
   4) All clients and servers MUST treat the $MDNSent keyword as case
   insensitive in all operations, as stated in [IMAP].

   C: a300 FETCH 1:* FLAGS
   S: * 1 FETCH (FLAGS (\Seen))
   S: * 2 FETCH (FLAGS (\Answered \Seen $MdnSENt))
   S: * 3 FETCH (FLAGS ())
   S: * 4 FETCH (FLAGS (\Flagged \Seen $MdnSENT))
   S: * 5 FETCH (FLAGS ($MDNSent))
   S: * 6 FETCH (FLAGS (\Recent))
   S: a300 OK FETCH completed
   C: a400 SEARCH KEYWORDS $mdnsent
   S: * SEARCH 2 4 5
   S: a400 OK SEARCH completed

6. Security Considerations

There are no known security issues with this extension, not found in [MDN] and/or [IMAP4]. Section 4.3 changes ACL checking requirements on an IMAP server that implements IMAP [ACL] extension.

7. Formal Syntax

The following syntax specification uses the augmented Backus-Naur Form (BNF) notation as specified in [RFC-822], as modified by [IMAP4]. Non-terminals referenced, but not defined below, are as defined by [IMAP4]. Except as noted otherwise, all alphabetic characters are case- insensitive. The use of upper or lower case characters to define token strings is for editorial clarity only. Implementations MUST accept these strings in a case-insensitive fashion. flag_keyword ::= "$MDNSent" / other_keywords other_keywords ::= atom

8. Acknowledgments

This document is the product of discussions that took place on the IMAP mailing list. Special gratitude to Cyrus Daboo and Randall Gellens for reviewing the document. Thank you to my father who as he has helped to make me what I am. I miss you terribly.
Top   ToC   RFC3503 - Page 8

9. Normative References

[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [MDN] Fajman, R., "An Extensible Message Format for Message Disposition Notifications", RFC 2298, March 1998. [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4rev1", RFC 3501, March 2003. [ACL] Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997.

10. Author's Address

Alexey Melnikov ACI Worldwide/MessagingDirect 59 Clarendon Road Watford, Hertfordshire United Kingdom, WD17 1FQ Phone: +44 1923 81 2877 EMail: mel@messagingdirect.com
Top   ToC   RFC3503 - Page 9

11. Full Copyright Statement

Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.