Registration of further IMAP/JMAP keywords and mailbox attribute names
draft-ietf-mailmaint-messageflag-mailboxattribute-00

MailMaint                                              N.M. Jenkins, Ed.
Internet-Draft                                                  Fastmail
Intended status: Informational                            D. Eggert, Ed.
Expires: 29 May 2025                                           Apple Inc
                                                        25 November 2024

 Registration of further IMAP/JMAP keywords and mailbox attribute names
          draft-ietf-mailmaint-messageflag-mailboxattribute-00

Abstract

   This document defines a number of keywords that have been in use by
   Fastmail and Apple respectively for some this.  It defines their
   intended use.  Additionally some mailbox names with special meaning
   have been in use by Fastmail, and this document defines their
   intended use.  This document registers all of these names with IANA
   to avoid name collisions.

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
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   This Internet-Draft will expire on 29 May 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  Flag Colors . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Definition of the MailFlagBit Message Keyword . . . . . .   4
     3.2.  Implementation Notes  . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  IMAP/JMAP Keyword Registrations . . . . . . . . . . . . .   5
       4.1.1.  $notify keyword registration  . . . . . . . . . . . .   5
       4.1.2.  $muted keyword registration . . . . . . . . . . . . .   6
       4.1.3.  $followed keyword registration  . . . . . . . . . . .   7
       4.1.4.  $memo keyword registration  . . . . . . . . . . . . .   7
       4.1.5.  $hasmemo keyword registration . . . . . . . . . . . .   8
       4.1.6.  $hasattachment keyword registration . . . . . . . . .   8
       4.1.7.  $autosent keyword registration  . . . . . . . . . . .   9
       4.1.8.  $unsubscribed keyword registration  . . . . . . . . .   9
       4.1.9.  $canunsubscribe keyword registration  . . . . . . . .  10
       4.1.10. $imported keyword registration  . . . . . . . . . . .  10
       4.1.11. $istrusted keyword registration . . . . . . . . . . .  10
       4.1.12. $maskedemail keyword registration . . . . . . . . . .  11
       4.1.13. $new keyword registration . . . . . . . . . . . . . .  12
       4.1.14. $MailFlagBit0 keyword registration  . . . . . . . . .  12
       4.1.15. $MailFlagBit1 keyword registration  . . . . . . . . .  12
       4.1.16. $MailFlagBit2 keyword registration  . . . . . . . . .  13
     4.2.  IMAP Mailbox Name Attributes Registrations  . . . . . . .  13
       4.2.1.  Snoozed mailbox name attribute registration . . . . .  13
       4.2.2.  Scheduled mailbox name attribute registration . . . .  13
       4.2.3.  Memos mailbox name attribute registration . . . . . .  14
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

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1.  Introduction

   The Internet Message Access Protocol (IMAP) specification [RFC9051]
   defines the use of message keywords, and an "IMAP Keywords" registry
   is created in [RFC5788].  Similarly [RFC8457] creates an "IMAP
   Mailbox Name Attributes Registry".

   This document does the following:

   *  Defines 16 message keywords

      -  $notify

      -  $muted

      -  $followed

      -  $memo

      -  $hasmemo

      -  $hasattachment

      -  $autosent

      -  $unsubscribed

      -  $canunsubscribe

      -  $imported

      -  $istrusted

      -  $maskedemail

      -  $new

      -  $MailFlagBit0

      -  $MailFlagBit1

      -  $MailFlagBit2

   *  Defines 3 mailbox name attributes

      -  Snoozed

      -  Scheduled

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      -  Memos

   *  Registers these in the "IMAP Keywords" registry and "IMAP Mailbox
      Name Attributes" registry respectively.

2.  Requirements Language

   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 in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Flag Colors

   The Internet Message Access Protocol (IMAP) specification [RFC9051]
   defines a \Flagged system flag to mark a message for urgent/special
   attention.  The new keywords defined in Sections 4.1.14, 4.1.15, and
   4.1.16 allow such a flagged message to have that flag be of one of 7
   colors.

3.1.  Definition of the MailFlagBit Message Keyword

   The 3 flag color keywords $MailFlagBit0, $MailFlagBit1, and
   $MailFlagBit2 make up a bit pattern that define the color of the flag
   as such:

                    +=======+=======+=======+========+
                    | Bit 0 | Bit 1 | Bit 2 | Color  |
                    +=======+=======+=======+========+
                    | 0     | 0     | 0     | red    |
                    +-------+-------+-------+--------+
                    | 1     | 0     | 0     | orange |
                    +-------+-------+-------+--------+
                    | 0     | 1     | 0     | yellow |
                    +-------+-------+-------+--------+
                    | 1     | 1     | 1     | green  |
                    +-------+-------+-------+--------+
                    | 0     | 0     | 1     | blue   |
                    +-------+-------+-------+--------+
                    | 1     | 0     | 1     | purple |
                    +-------+-------+-------+--------+
                    | 0     | 1     | 1     | gray   |
                    +-------+-------+-------+--------+

                           Table 1: Flag Colors

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   These flags SHOULD be ignored if the \Flagged system flag is not set.
   If the \Flagged system flag is set, the flagged status MAY be
   displayed to the user in the color corresponding to the combination
   of the 3 flag color keywords.

3.2.  Implementation Notes

   A mail client that is aware of these flag color keywords SHOULD clear
   all 3 flag color keywords when the user unflags the message, i.e.
   when unsetting the \Flagged system flag, all 3 flag color keywords
   SHOULD also be unset.

   A mail client SHOULD NOT set any of these flags unless the \Flagged
   system flag is already set or is being set.

   Servers MAY unset these flag color keywords when a client unsets the
   \Flagged system flag.

4.  IANA Considerations

   3 IMAP/JMAP keywords are registered in the IMAP/JMAP keywords
   registry, as established in RFC5788.

4.1.  IMAP/JMAP Keyword Registrations

4.1.1.  $notify keyword registration

   IMAP/JMAP keyword name:  $notify
   Purpose:  Indicate to the client that a notification should be shown
      for this message.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword can cause automatic action.  On supporting clients, when a
      new message is added to the mailstore with this keyword, the
      client should show the user a notification.
      Mail clients commonly show notifications for new mail, but often
      the only option is to show a notification for every message that
      arrvies in the inbox.  This keyword allows the user to create
      rules (or the server to automatically determine) specific messages
      that should show a notification.
      Notifications for these messages may be in addition to
      notifications for messages matching other criteria, according to
      user preference set on the client.
   When/by whom the keyword is set/cleared:  This keyword is set by an

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      IMAP or JMAP server on delivery when a message meets criteria such
      that the user should be shown a notification.  It may be cleared
      by a client when the user opens, archives, or otherwise interacts
      with th message.  Other clients connected to the same account may
      choose to automatically close the notification if the flag is
      cleared.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.2.  $muted keyword registration

   IMAP/JMAP keyword name:  $muted
   Purpose:  Indicate to the server that the user is not interested in
      future replies to a particular thread.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword can cause automatic action.  On supporting servers, when a
      new message arrives that is in the same thread as a message with
      this keyword the server may automatically process it in some way
      to deprioritise it for the user, for example by moving it to the
      archive or trash, or marking it read.  The exact action, whether
      this is customisable by the user, and interaction with user rules
      is vendor specific.
      A message is defined to be in the same thread as another if the
      server assigns them both the same thread id, as defined in
      [RFC8474] Section 5.2 for IMAP or [RFC8621], Section 3 for JMAP.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client when the user indicates they wish to mute or
      unmute a thread.  When unmuting a thread, the client must remove
      the keyword from every message in the thread that has it.
   Related keywords:  Mutually exclusive with $followed.  If both are
      specified on a thread, servers MUST behave as though only
      $followed were set.
   Related IMAP capabilities:  None
   Security considerations:  Muting a thread can mean a user won't see a
      reply.  If someone compromises a user's account, they may mute
      threads where they don't want the user to see the reply, for
      example when sending phishing to the user's contacts.  There are
      many other ways an attacker with access to the user's mailbox can
      also achieve this however, so this is not greatly increasing the
      attack surface.
   Published specification:  This document
   Intended usage:  COMMON

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   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.3.  $followed keyword registration

   IMAP/JMAP keyword name:  $followed
   Purpose:  Indicate to the server that the user is particularly
      interested in future replies to a particular thread.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword can cause automatic action.  On supporting servers, when a
      new message arrives that is in the same thread as a message with
      this keyword the server may automatically process it in some way
      to prioritise it for the user, for example by ignoring rules that
      would make it skip the inbox, or automatically adding the $notify
      keyword.  The exact action, whether this is customisable by the
      user, and interaction with user rules is vendor specific.
      A message is defined to be in the same thread as another if the
      server assigns them both the same thread id, as defined in
      [RFC8474] Section 5.2 for IMAP or [RFC8621], Section 3 for JMAP.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client when the user indicates they wish to follow or
      unfollow a thread.  When unfollowing a thread, the client must
      remove the keyword from every message in the thread that has it.
   Related keywords:  Mutually exclusive with $muted.  If both are
      specified on a thread, servers MUST behave as though only
      $followed were set.
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.4.  $memo keyword registration

   IMAP/JMAP keyword name:  $memo
   Purpose:  Indicate to the client that a message is a note-to-self
      from the user regarding another message in the same thread.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client when creating such a message.  The message
      should otherwise be contructed like a reply to the message to
      which this memo is attached (i.e. appropriate Subject and Reply-To
      headers set).  In supporting clients, messages with this flag may
      be presented differently to the user, attached to the message the

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      memo is commenting on, and may offer the user the ability to edit
      or delete the memo.  (As messages are immutable, editing requires
      replacing the message.)
   Related keywords:  The $hasmemo keyword should be set/cleared at the
      same time.
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.5.  $hasmemo keyword registration

   IMAP/JMAP keyword name:  $hasmemo
   Purpose:  Indicate to the client that a message has an associated
      memo with the $memo keyword.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client when creating a memo.  The memo gets the $memo
      keyword, the message it is a note for gets the $hasmemo keyword.
      This keyword can help in searching for messages with memos, or
      deciding whether to fetch the whole thread to look for memos when
      loading a mailbox.
   Related keywords:  A message with the $memo keyword should be
      created/destroyed at the same time.
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.6.  $hasattachment keyword registration

   IMAP/JMAP keyword name:  $hasattachment
   Purpose:  Indicate to the client that a message has an attachment.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on messages it determines have an attachment.
      This can help mailbox clients indicate this to the user without
      having to fetch the full message body structure.  Over JMAP, the
      "hasAttachment" Email property should indicate the same value.
   Related keywords:  None

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   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.7.  $autosent keyword registration

   IMAP/JMAP keyword name:  $autosent
   Purpose:  Indicate to the client that a message was sent
      automatically as a response due to a user rule or setting.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on the user's copy of their vacation response
      and other automated messages sent on behalf of the user.  Clients
      may use this to indicate to the user that this message was sent
      automatically, as if they have forgotten the rule or vacation
      response is set up they may be surprised to see it among their
      sent items.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.8.  $unsubscribed keyword registration

   IMAP/JMAP keyword name:  $unsubscribed
   Purpose:  Indicate to the client that it has unsubscribed from the
      thread this message is on.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client on a message after attempting to unsubscribe
      from the mailing list this message came from (e.g., after
      attempting RFC8058 one-click List-Unsubscribe).  It allows clients
      to remind the user that they have unsubscribed if they open the
      message again.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document

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   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.9.  $canunsubscribe keyword registration

   IMAP/JMAP keyword name:  $canunsubscribe
   Purpose:  Indicate to the client that this message has an
      RFC8058-compliant List-Unsubscribe header.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on messages with an RFC8058-compliant List-
      Unsubscribe header.  It may only do so if the message passes
      vendor-specific reputation checks.  It is intended to indicate to
      clients that they may be able to do a one-click unsubscribe,
      without them having to fetch the List-Unsubscribe header to
      determint themself.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.10.  $imported keyword registration

   IMAP/JMAP keyword name:  $imported
   Purpose:  Indicate to the client that this message was imported from
      another mailbox.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on messages in imports from another mailbox.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.11.  $istrusted keyword registration

   IMAP/JMAP keyword name:  $istrusted

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   Purpose:  Indicate to the client that the authenticity of the from
      name and email address have been verified with complete confidence
      by the server.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.  Clients may show a verification mark (often
      a tick icon) on messages with this keyword to indicate their
      trusted status to the user.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on messages it delivers where it wishes to
      confirm to the user that this is a legitimate email they can
      trust.  It is usually only used for the mailbox provider's own
      messages to the customer, where they can know with absolute
      certainty that the friendly from name and email address are
      legitimate.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  Servers should make sure this keyword is
      only set for messages that really are trusted!
   Published specification:  This document
   Intended usage:  COMMON
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.12.  $maskedemail keyword registration

   IMAP/JMAP keyword name:  $maskedemail
   Purpose:  Indicate to the client that the message was received via an
      alias created for an individual sender.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.  Clients may show an icon to indicate to the
      user this was received via a masked email address - an alias
      created for a specific sender to hide the user's real email
      address.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on messages it delivers that arrived via such
      an alias.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  LIMITED
   Scope:  BOTH
   Owner/Change controller:  IESG

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4.1.13.  $new keyword registration

   IMAP/JMAP keyword name:  $new
   Purpose:  Indicate to the client that a message should be made more
      prominent to the user due to a recent action.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  This 
      keyword is advisory.  Clients may show the status of the message.
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP server on messages after awakening them from snooze.
      Clients should clear the keyword when the message is opened.
   Related keywords:  None
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  LIMITED
   Scope:  BOTH
   Owner/Change controller:  IESG

4.1.14.  $MailFlagBit0 keyword registration

   IMAP/JMAP keyword name:  $MailFlagBit0
   Purpose:  0 bit part of a 3-bit bitmask that defines the color of the
      flag when the has the system flag \Flagged set.  See Section 3 for
      details.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  No
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client as the result of a user action to "flag" a
      message for urgent/special attention.
   Related keywords:  $MailFlagBit1, $MailFlagBit2
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Owner/Change controller:  IESG

4.1.15.  $MailFlagBit1 keyword registration

   IMAP/JMAP keyword name:  $MailFlagBit1
   Purpose:  0 bit part of a 3-bit bitmask that defines the color of the
      flag when the has the system flag \Flagged set.  See Section 3 for
      details.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  No
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client as the result of a user action to "flag" a
      message for urgent/special attention.

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   Related keywords:  $MailFlagBit0, $MailFlagBit2
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Owner/Change controller:  IESG

4.1.16.  $MailFlagBit2 keyword registration

   IMAP/JMAP keyword name:  $MailFlagBit2
   Purpose:  0 bit part of a 3-bit bitmask that defines the color of the
      flag when the has the system flag \Flagged set.  See Section 3 for
      details.
   Private or Shared on a server:  SHARED
   Is it an advisory keyword or may it cause an automatic action:  No
   When/by whom the keyword is set/cleared:  This keyword is set by an
      IMAP or JMAP client as the result of a user action to "flag" a
      message for urgent/special attention.
   Related keywords:  $MailFlagBit0, $MailFlagBit1
   Related IMAP capabilities:  None
   Security considerations:  None
   Published specification:  This document
   Intended usage:  COMMON
   Owner/Change controller:  IESG

4.2.  IMAP Mailbox Name Attributes Registrations

4.2.1.  Snoozed mailbox name attribute registration

   Attribute Name:  Snoozed
   Description:  Messages that have been snoozed are moved to this
      mailbox until the "awaken" time, when they are moved out of it
      again automatically by the server.
   Reference:  This document.
   Usage Notes:  Snooze functionality is common among services but not
      yet standardised.  This attribute marks the mailbox where snoozed
      messages may be found, but does not on its own provide a way for
      clients to snooze messages.

4.2.2.  Scheduled mailbox name attribute registration

   Attribute Name:  Scheduled
   Description:  Messages that have been scheduled to send at a later
      time.  Once the server has sent them at the scheduled time, they
      will automatically be deleted or moved from this mailbox by the
      server (probably to the \Sent mailbox).
   Reference:  This document.
   Usage Notes:  Scheduled sending functionality is common among

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      services but not yet standardised.  This attribute marks the
      mailbox where scheduled messages may be found, but does not on its
      own provide a way for clients to schedule messages for sending.

4.2.3.  Memos mailbox name attribute registration

   Attribute Name:  Memos
   Description:  Messages that have the $memo keyword.  Clients creating
      memos are recommended to store them in this mailbox.  This allows
      them to more easily be hidden from the user as "messages", and
      presented only as memos instead.
   Reference:  This document.
   Usage Notes:  None.

5.  Security Considerations

   This document should not affect the security of the Internet.

6.  References

6.1.  Normative References

   [RFC2119]  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/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8457]  Leiba, B., Ed., "IMAP "$Important" Keyword and
              "\Important" Special-Use Attribute", RFC 8457,
              DOI 10.17487/RFC8457, September 2018,
              <https://www.rfc-editor.org/info/rfc8457>.

   [RFC8474]  Gondwana, B., Ed., "IMAP Extension for Object
              Identifiers", RFC 8474, DOI 10.17487/RFC8474, September
              2018, <https://www.rfc-editor.org/info/rfc8474>.

   [RFC8621]  Jenkins, N. and C. Newman, "The JSON Meta Application
              Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621,
              August 2019, <https://www.rfc-editor.org/info/rfc8621>.

   [RFC9051]  Melnikov, A., Ed. and B. Leiba, Ed., "Internet Message
              Access Protocol (IMAP) - Version 4rev2", RFC 9051,
              DOI 10.17487/RFC9051, August 2021,
              <https://www.rfc-editor.org/info/rfc9051>.

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   [RFC5788]  Melnikov, A. and D. Cridland, "IMAP4 Keyword Registry",
              RFC 5788, DOI 10.17487/RFC5788, March 2010,
              <https://www.rfc-editor.org/info/rfc5788>.

Authors' Addresses

   Neil Jenkins (editor)
   Fastmail
   PO Box 234, Collins St West
   Melbourne  VIC 8007
   Australia
   Email: neilj@fastmailteam.com
   URI:   https://www.fastmail.com

   Daniel Eggert (editor)
   Apple Inc
   One Apple Park Way
   Cupertino,  CA 95014
   United States of America
   Email: deggert@apple.com
   URI:   https://www.apple.com

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