IMAP "$Important" Keyword and "\Important" Special-Use Attribute
RFC 8457

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Internet Engineering Task Force (IETF)                     B. Leiba, Ed.
Request for Comments: 8457                           Huawei Technologies
Category: Standards Track                                 September 2018
ISSN: 2070-1721

    IMAP "$Important" Keyword and "\Important" Special-Use Attribute

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, which include the attributes defined in RFCs 5258, 3501,
   and 6154.  This document also defines a new IMAP keyword,
   "$Important", and registers it in the registry defined in RFC 5788.

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/rfc8457.

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
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   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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   1.1.  Conventions Used in This Document . . . . . . . . . . . . .   3
   2.  Definition of the "$Important" Message Keyword  . . . . . . .   3
   3.  Definition of the 'Important' Mailbox Attribute . . . . . . .   3
   3.1.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . .   4
   3.2.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.2.1.  Example of a LIST Response  . . . . . . . . . . . . . . .   4
   3.2.2.  Examples of Creating a New Mailbox Using "\Important" . .   4
   4.  Implementation Notes  . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.1.  Registration of the "$Important" Keyword  . . . . . . . . .   6
   6.2.  Creation of the IMAP Mailbox Name Attributes Registry . . .   7
   6.2.1.  Instructions to the Designated Expert . . . . . . . . . .   8
   6.3.  Initial Entries for the IMAP Mailbox Name Attributes
         Registry  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
   7.1.  Normative References  . . . . . . . . . . . . . . . . . . .  10
   7.2.  Informative References  . . . . . . . . . . . . . . . . . .  10
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The Internet Message Access Protocol (IMAP) specification [RFC3501]
   defines the use of message keywords, and an "IMAP Keywords" registry
   is created in [RFC5788].  [RFC6154] defines an extension to the IMAP
   LIST command 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.

   This document does the following:

   o  defines a new message keyword, "$Important", to apply to messages
      that are considered important for the user by some externally
      defined criteria;

   o  registers the "$Important" keyword in the "IMAP Keywords"
      registry;

   o  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; and

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   o  creates a registry for IMAP mailbox attributes and registers the
      new attribute and those defined in [RFC5258], [RFC3501], and
      [RFC6154].

1.1.  Conventions Used in This Document

   In the examples used in this document, "C:" indicates lines sent by a