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Versions: 00 01 02

Network Working Group                                           B. Leiba
Internet-Draft                                       Huawei Technologies
Updates: 3348,3501,6154                                        E. Iceman
(if approved)                                               Google, Inc.
Intended status: Standards Track                        January 17, 2013
Expires: July 21, 2013


              IMAP LIST Special-Use Attribute: \Important
               draft-iceman-imap-specialuse-important-01

Abstract

   RFC 6154 created an IMAP Special-Use LIST extension and defined an
   initial set of attributes.  This document defines a new attribute,
   "\Important", and establishes a new IANA registry for IMAP folder
   attributes, updating RFCs 3348, 3501, and 6154.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 21, 2013.

Copyright Notice

   Copyright (c) 2013 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
   (http://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



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   described in the Simplified BSD License.


Table of Contents

   1.    Introduction  . . . . . . . . . . . . . . . . . . . . . . . . 3
   1.1.  Conventions used in this document . . . . . . . . . . . . . . 3

   2.    Definition of the 'Important' Attribute . . . . . . . . . . . 3
   2.1.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.2.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

   3.    Security Considerations . . . . . . . . . . . . . . . . . . . 4

   4.    IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
   4.1.  Creation of the IMAP LIST Special-Use Attributes Registry . . 4
   4.2.  Initial entries for the registry  . . . . . . . . . . . . . . 5
   4.3.  Instructions to the Designated Expert . . . . . . . . . . . . 6

   5.    Changes During Document Development . . . . . . . . . . . . . 7

   6.    References  . . . . . . . . . . . . . . . . . . . . . . . . . 7
   6.1.  Normative References  . . . . . . . . . . . . . . . . . . . . 7
   6.2.  Informative References  . . . . . . . . . . . . . . . . . . . 7

         Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . 7

























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1.  Introduction

   [RFC6154] defines an extension to the Internet Message Access
   Protocol (IMAP) LIST command [RFC3501] for special-use mailboxes.
   The extension allows servers to provide extra information
   (attributes) about the purpose of a mailbox and defines an initial
   set of special-use attributes.  There are now three RFCs that define
   mailbox attributes, and no registry for those attributes.

   This document defines a new special-use attribute, "\Important", to
   designate a mailbox that will hold messages that are considered
   important for the user, by some externally defined criteria.  This
   document also creates a registry for IMAP mailbox attributes and
   registers both the new attribute and those defined earlier, updating
   [RFC3348], [RFC3501], and [RFC6154].

1.1.  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.


2.  Definition of the 'Important' Attribute

   The "\Important" mailbox attribute is a signal that the mailbox
   contains messages that are likely important to the user.  For
   example, the system might automatically put messages there based on
   available signals (such as who the message is from, who else the
   message is addressed to, evaluation of the subject or content).  Or
   it might be a way for users to train the system as to what messages
   are important (the system can learn patterns from the messages the
   user copies to that mailbox).

   [[anchor4: Possible change here: Cyrus has suggested (1) removal of
   the last sentence above, about learning, and (2) definition of an
   $Important message keyword, and reference to \Important as a virtual
   mailbox to collect all such messages (as \Flagged does).]]

   This is distinct from the "\Flagged" attribute in that evaluation of
   importance here is based on heuristics, whereas "\Flagged" is
   typically based on the setting of the IMAP flag of the same name.

2.1.  Formal Syntax

   The following syntax specification updates the one in [RFC6154],
   Section 6, using Augmented Backus-Naur Form (ABNF) as described in
   [RFC5234].




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       use-attr      =/  "\Important"

2.2.  Example

   In the following example, the mailbox called "Important Messages" is
   the one designated with the "\Important" attribute.

       C: t1 list "" "Imp*"
       S: * LIST (\HasNoChildren \Important) "/" "Important Messages"
       S: * LIST (\HasNoChildren) "/" "Imported Wine"
       S: t1 OK Success


3.  Security Considerations

   The security considerations in [RFC6154], Section 7, apply equally to
   this extension.  In particular, "Conveying special-use information to
   a client exposes a small bit of extra information that could be of
   value to an attacker."  Moreover, identifying a place where
   "important" messages are kept could give an attacker a strategic
   starting point.  If the algorithm by which messages are determined to
   be important is well known, still more information is exposed --
   perhaps, for example, there is an implication that the senders of
   these messages are particularly significant to the mailbox owner, and
   perhaps that is information that should not be made public.

   As noted in RFC 6154, it is wise to protect the IMAP channel from
   passive eavesdropping, and to defend against unauthorized discernment
   of the identity of a user's "\Important" mailbox.


4.  IANA Considerations

   [[RFC Editor: Please replace "THIS RFC" throughout this section with
   the identification given to this document, and remove this
   paragraph.]]

4.1.  Creation of the IMAP LIST Special-Use Attributes Registry

   IANA is asked to create a new registry in the group "Internet Message
   Access Protocol (IMAP) 4 Registries".  The new registry will be
   called "IMAP Mailbox Name Attributes", and will have two references:
   RFC 3501, Section 7.2.2, and THIS RFC, Section 4.

   The registry entries will contain three fields:






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   1.  Attribute Name
   2.  Description
   3.  Reference

   IANA will keep this list in alphabetical order by Attribute Name,
   which is registered without the initial backslash ("\").

   New registrations will be accepted through the Expert Review policy
   [RFC5226] (and see Section 4.3).  New registrations are requested
   through the IANA Considerations section in an RFC, or, for requests
   that do not come from an RFC, by sending email to IANA asking for a
   new IMAP Mailbox Name Attribute and giving the requested values for
   each of the three fields.

4.2.  Initial entries for the registry

   The registry will initially contain these entries:


































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   +===============+===================================+===========+
   | Attribute     | Description                       | Reference |
   | Name          |                                   |           |
   +===============+===================================+===========+
   | All           | All messages                      | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | Archive       | Archived messages                 | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | Drafts        | Messages that are working drafts  | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | Flagged       | Messages with the \Flagged flag   | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | HasChildren   | Has accessible child mailboxes    | [RFC3348] |
   +---------------+-----------------------------------+-----------+
   | HasNoChildren | Has no accessible child mailboxes | [RFC3348] |
   +---------------+-----------------------------------+-----------+
   | Important     | Messages deemed important to user | THIS RFC  |
   +---------------+-----------------------------------+-----------+
   | Junk          | Messages identified as Spam/Junk  | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | Marked        | Server has marked the mailbox as  | [RFC3501] |
   |               | "interesting"                     |           |
   +---------------+-----------------------------------+-----------+
   | NoInferiors   | No hierarchy under this name      | [RFC3501] |
   +---------------+-----------------------------------+-----------+
   | Noselect      | The mailbox is not selectable     | [RFC3501] |
   +---------------+-----------------------------------+-----------+
   | Sent          | Sent mail                         | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | Trash         | Messages the user has discarded   | [RFC6154] |
   +---------------+-----------------------------------+-----------+
   | Unmarked      | No new messages since last select | [RFC3501] |
   +===============+===================================+===========+

4.3.  Instructions to the Designated Expert

   The expert reviewer, who will be designated by the IESG, is expected
   to provide only a general review of the requested registration,
   checking that the reference and description are adequate for
   understanding the intent of the registered attribute.  Efforts should
   also be made to generalize the intent of an attribute so that
   multiple implementations with the same requirements may reuse
   existing attributes.  Except for this check, this is intended to be
   very close to a first come first served policy, and the expert should
   not block serious registration requests with a reasonable reference.
   The reference may be to any form of documentation, including a web
   page, but consideration should be given to providing one that is
   expected to be long-lived and stable.



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5.  Changes During Document Development

   [[anchor11: RFC Editor: Please remove this section prior to
   publication.]]

   Changes in -01
   o  Expanded the new registry to all mailbox name attributes, and
      added the attributes from 3501 and 3348 (suggested by Alexey).
      This also adds those two documents to the "updates" list.
   o  Recorded Cyrus's suggestion to define $Important.


6.  References

6.1.  Normative References

   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
              4rev1", RFC 3501, March 2003.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC6154]  Leiba, B. and J. Nicolson, "IMAP LIST Extension for
              Special-Use Mailboxes", RFC 6154, March 2011.

6.2.  Informative References

   [RFC3348]  Gahrns, M. and R. Cheng, "The Internet Message Action
              Protocol (IMAP4) Child Mailbox Extension", RFC 3348,
              July 2002.


Authors' Addresses

   Barry Leiba
   Huawei Technologies

   Phone: +1 646 827 0648
   Email: barryleiba@computer.org
   URI:   http://internetmessagingtechnology.org/







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   Eric Iceman
   Google, Inc.

   Email: iceman@google.com















































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