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Internet Engineering Task Force (IETF)                          S. BoschRequest for Comments: 8514                               Open Xchange OyCategory: Standards Track                                   January 2019ISSN: 2070-1721Internet Message Access Protocol (IMAP) - SAVEDATE ExtensionAbstract   This document adds a new capability called "SAVEDATE" to the Internet   Message Access Protocol (IMAP).  It defines a new IMAP message   attribute called "save date" that, unlike the existing "internal   date" attribute, always indicates the moment at which the message was   saved in its current mailbox.  The SAVEDATE capability extends the   FETCH command with the means to retrieve the save date attribute and   extends the SEARCH command to allow using the save date attribute in   searching criteria.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttps://www.rfc-editor.org/info/rfc8514.Copyright Notice   Copyright (c) 2019 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (https://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Bosch                        Standards Track                    [Page 1]

RFC 8514                IMAP - SAVEDATE Extension           January 2019Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions Used in This Document . . . . . . . . . . . . . .33.  Save Date Message Attribute . . . . . . . . . . . . . . . . .34.  IMAP Protocol Changes . . . . . . . . . . . . . . . . . . . .44.1.  CAPABILITY Identification . . . . . . . . . . . . . . . .44.2.  FETCH Command and Response Extensions . . . . . . . . . .44.3.  SEARCH Command Extension  . . . . . . . . . . . . . . . .45.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . .56.  Security Considerations . . . . . . . . . . . . . . . . . . .57.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .68.  Normative References  . . . . . . . . . . . . . . . . . . . .6   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .7   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .71.  Introduction   This document extends the Internet Message Access Protocol (IMAP)   [IMAP4rev1] with a new capability called "SAVEDATE".  This capability   adds a new IMAP message attribute called "save date".  The save date   is the date and time at which a message was saved in the mailbox in   which it currently resides.  The save date is similar to the existing   "internal date" attribute in that it is set at the time of delivery.   However, the internal date attribute can be set to an arbitrary value   for messages delivered to the mailbox using the APPEND command and is   usually copied from the source message for messages delivered using   the COPY command.  In contrast, the save date attribute is always set   to the current date and time at the moment the message is saved in   the mailbox, irrespective of how the message is delivered and from   where it originates.   The save date attribute is useful for implementing automated removal   of messages from a mailbox after a configured amount of time.  For   that application, it is necessary to know when the message was saved   in the mailbox, which cannot be reliably determined using the   internal date attribute.   For example, a common client usage pattern is to move deleted   messages to a Trash mailbox.  These messages are considered "deleted"   at the time they are moved to the Trash mailbox.  In an effort to   limit the size of the Trash mailbox, a client may subsequently desire   to permanently remove (expunge) all messages in that Trash mailbox   deleted before a certain time (e.g., a configurable expiration   interval).  In that case, the internal date attribute cannot be used   since it likely refers to the time at which the message was   originally received.  The proper time comparison attribute shouldBosch                        Standards Track                    [Page 2]

RFC 8514                IMAP - SAVEDATE Extension           January 2019   instead be the time at which the message was saved to the Trash   mailbox.  Similar usage patterns can be observed for archiving   solutions.   The SAVEDATE capability extends the FETCH command and response to   allow retrieving the date and time at which a message was saved.   Also, the SAVEDATE capability extends the SEARCH command to allow   searching messages with criteria based on when they were saved in the   mailbox.2.  Conventions Used in This Document   In examples, "C:" indicates lines sent by a client that is connected   to a server.  "S:" indicates lines sent by the server to the client.   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described inBCP 14 [KEYWORDS] [KEYWORDS-UPD] when, and only when, they appear in   all capitals, as shown here.3.  Save Date Message Attribute   The save date message attribute is the date and time at which the   message was saved in the mailbox it is now located in.  Unlike the   internal date message attribute defined by [IMAP4rev1], this date and   time value cannot be set arbitrarily when a message is delivered by   the IMAP APPEND command.  Also, when a message is delivered to the   mailbox by the IMAP COPY command [IMAP4rev1] or the IMAP MOVE command   [IMAP-MOVE], the save date attribute is not copied from the source   message.  Instead, the current date and time at which the message is   delivered to a mailbox MUST be used to set the save date attribute.   Once calculated, the save date attribute MUST NOT change as long as   the message is contained within the same mailbox.   This means that when the message is copied to another mailbox, the   save date of the message in the source mailbox remains unaffected;   only the new copy of the message gets a new save date.  Consequently,   when the message is moved to another mailbox, either using the MOVE   command or a command sequence involving the COPY command [IMAP-MOVE],   the message always gets a new save date in the destination mailbox.   For some specific mailboxes, the underlying storage may not support   the save date attribute.  The handling of this situation is described   in detail in the next section for each involved IMAP command.Bosch                        Standards Track                    [Page 3]

RFC 8514                IMAP - SAVEDATE Extension           January 20194.  IMAP Protocol Changes4.1.  CAPABILITY Identification   IMAP servers that support this extension MUST include "SAVEDATE" in   the response list to the CAPABILITY command.4.2.  FETCH Command and Response Extensions   This extension defines one new data item for the FETCH command:   SAVEDATE      The save date of the message.   This extension defines one new data item for the FETCH response:   SAVEDATE      A string representing the save date of the message.  However, if      the underlying mailbox storage does not support the save date      message attribute, the value returned for the SAVEDATE item is      always NIL, rather than a string.   Example:         C: A101 FETCH 998 (SAVEDATE)         S: * 998 FETCH (SAVEDATE "01-Jan-2015 18:50:53 +0100")         S: A101 OK Fetch completed.4.3.  SEARCH Command Extension   This extension defines four new search keys for the SEARCH command:   SAVEDBEFORE <date>      Messages whose save date (disregarding time and timezone) is      earlier than the specified date.   SAVEDON <date>      Messages whose save date (disregarding time and timezone) is      within the specified date.   SAVEDSINCE <date>      Messages whose save date (disregarding time and timezone) is      within or later than the specified date.Bosch                        Standards Track                    [Page 4]

RFC 8514                IMAP - SAVEDATE Extension           January 2019   SAVEDATESUPPORTED      Matches all messages in the mailbox when the underlying storage of      that mailbox supports the save date attribute.  Conversely, it      matches no messages in the mailbox when the save date attribute is      not supported.   When the underlying storage of a mailbox does not support the save   date attribute, the SAVEDBEFORE, SAVEDON, and SAVEDSINCE search keys   MUST use the internal date attribute instead.  In the context of the   IMAP Multimailbox SEARCH Extension [MULTISEARCH], this fallback   behavior MUST apply to each mailbox individually, meaning that only   the mailboxes that lack support for the save date attribute use the   internal date attribute instead.   Example:         C: A102 SEARCH SAVEDON 28-Dec-2014         S: * SEARCH 993 994         S: A102 OK Search completed.         C: A103 SEARCH SAVEDSINCE 28-Dec-2014         S: * SEARCH 993 994 995 996 997 998 999 1000 1001         S: A103 OK Search completed.5.  Formal Syntax   The following syntax specification augments the grammar specified in   [IMAP4rev1].  It uses the Augmented Backus-Naur Form (ABNF) notation   as specified in [ABNF].  Elements not defined here are taken from   [IMAP4rev1].   capability     =/ "SAVEDATE"   fetch-att      =/ "SAVEDATE"   msg-att-static =/ "SAVEDATE" SP (date-time / nil)   search-key     =/ "SAVEDBEFORE" SP date /                     "SAVEDON" SP date /                     "SAVEDSINCE" SP date /                     "SAVEDATESUPPORTED"6.  Security Considerations   There are no known additional security issues with this extension   beyond those described in the base protocol described in [IMAP4rev1].Bosch                        Standards Track                    [Page 5]

RFC 8514                IMAP - SAVEDATE Extension           January 20197.  IANA Considerations   IANA has added "SAVEDATE" to the "IMAP Capabilities" registry located   at <https://www.iana.org/assignments/imap-capabilities>.8.  Normative References   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax              Specifications: ABNF", STD 68,RFC 5234,              DOI 10.17487/RFC5234, January 2008,              <https://www.rfc-editor.org/rfc/rfc5234>.   [IMAP-MOVE]              Gulbrandsen, A. and N. Freed, "Internet Message Access              Protocol (IMAP) - MOVE Extension",RFC 6851,              DOI 10.17487/RFC6851, January 2013,              <https://www.rfc-editor.org/rfc/rfc6851>.   [IMAP4rev1]              Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION              4rev1",RFC 3501, DOI 10.17487/RFC3501, March 2003,              <https://www.rfc-editor.org/rfc/rfc3501>.   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <https://www.rfc-editor.org/rfc/rfc2119>.   [KEYWORDS-UPD]              Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.   [MULTISEARCH]              Leiba, B. and A. Melnikov, "IMAP4 Multimailbox SEARCH              Extension",RFC 7377, DOI 10.17487/RFC7377, October 2014,              <https://www.rfc-editor.org/info/rfc7377>.Bosch                        Standards Track                    [Page 6]

RFC 8514                IMAP - SAVEDATE Extension           January 2019Acknowledgements   Thanks to Bron Gondwana, Alexey Melnikov, Timo Sirainen, and Michael   Slusarz for reviews and suggestions.Author's Address   Stephan Bosch   Open Xchange Oy   Lars Sonckin kaari 12   Espoo  02600   Finland   Email: stephan.bosch@open-xchange.comBosch                        Standards Track                    [Page 7]