IMAP Extension for Object Identifiers
RFC 8474

Document Type RFC - Proposed Standard (September 2018; No errata)
Updates RFC 3501
Last updated 2018-09-25
Replaces draft-ietf-extra-imap-uniqueid
Stream IETF
Formats plain text pdf html bibtex
Reviews SECDIR will not review this version
Stream WG state Submitted to IESG for Publication
Document shepherd Jiankang Yao
Shepherd write-up Show (last changed 2018-06-21)
IESG IESG state RFC 8474 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Alexey Melnikov
Send notices to Jiankang Yao <yaojk@cnnic.cn>;aamelnikov@fastmail.fm
IANA IANA review state IANA OK - Actions Needed
IANA action state RFC-Ed-Ack
Internet Engineering Task Force (IETF)                  B. Gondwana, Ed.
Request for Comments: 8474                                      FastMail
Updates: 3501                                             September 2018
Category: Standards Track
ISSN: 2070-1721

                 IMAP Extension for Object Identifiers

Abstract

   This document updates RFC 3501 (IMAP4rev1) with persistent
   identifiers on mailboxes and messages to allow clients to more
   efficiently reuse cached data when resources have changed location on
   the server.

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 in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8474.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 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.

Gondwana                     Standards Track                    [Page 1]
RFC 8474                      IMAP ObjectID               September 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
   3.  CAPABILITY Identification . . . . . . . . . . . . . . . . . .   3
   4.  MAILBOXID Object Identifier . . . . . . . . . . . . . . . . .   3
     4.1.  New Response Code for CREATE  . . . . . . . . . . . . . .   4
     4.2.  New OK Untagged Response for SELECT and EXAMINE . . . . .   4
     4.3.  New Attribute for STATUS  . . . . . . . . . . . . . . . .   5
   5.  EMAILID Object Identifier and THREADID Correlator . . . . . .   6
     5.1.  EMAILID Identifier for Identical Messages . . . . . . . .   6
     5.2.  THREADID Identifier for Related Messages  . . . . . . . .   6
     5.3.  New Message Data Items in FETCH and UID FETCH Commands  .   7
   6.  New Filters on SEARCH Command . . . . . . . . . . . . . . . .   9
   7.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Implementation Considerations . . . . . . . . . . . . . . . .  10
     8.1.  Assigning Object Identifiers  . . . . . . . . . . . . . .  10
     8.2.  Interaction with Special Cases  . . . . . . . . . . . . .  11
     8.3.  Client Usage  . . . . . . . . . . . . . . . . . . . . . .  11
     8.4.  Advice to Client Implementers . . . . . . . . . . . . . .  12
   9.  Future Considerations . . . . . . . . . . . . . . . . . . . .  12
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     12.2.  Informative References . . . . . . . . . . . . . . . . .  14
   Appendix A.  Ideas for Implementing Object Identifiers  . . . . .  15
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   IMAP stores are often used by many clients.  Each client may cache
   data from the server so that it doesn't need to redownload
   information.  [RFC3501] states that a mailbox can be uniquely
   referenced by its name and UIDVALIDITY, and a message within that
   mailbox can be uniquely referenced by its mailbox (name +
   UIDVALIDITY) and unique identifier (UID).  The triple of mailbox
   name, UIDVALIDITY, and UID is guaranteed to be immutable.

   [RFC4315] defines a COPYUID response that allows a client that copies
   messages to know the mapping between the UIDs in the source and
   destination mailboxes and, hence, update its local cache.

   If a mailbox is successfully renamed by a client, that client will
   know that the same messages exist in the destination mailbox name as
   previously existed in the source mailbox name.

Gondwana                     Standards Track                    [Page 2]
RFC 8474                      IMAP ObjectID               September 2018

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