Network Working Group

Internet Engineering Task Force (IETF)                       A. Melnikov
Internet-Draft
Request for Comments: 9122                                     Isode Ltd
Intended status:
Category: Standards Track                                   K. Murchison
Expires: 28 September 2023
ISSN: 2070-1721                                                 Fastmail
                                                           27 March
                                                               June 2023

                    IANA registry Registry for Sieve actions
               draft-ietf-extra-sieve-action-registry-06 Actions

Abstract

   The Sieve Email Filtering Language (RFC 5228) is a popular email
   filtering language used upon final mail delivery.  This document
   creates a registry of for Sieve (RFC 5228) actions in order to help developers and Sieve
   extension writers track interactions between different extensions.

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 an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list  It represents the consensus of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid the IETF community.  It has
   received public review and has been approved for a maximum publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of six months RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 28 September 2023.
   https://www.rfc-editor.org/info/rfc9122.

Copyright Notice

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   document authors.  All rights reserved.

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   in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Sieve Actions Registration Template and Procedure . . . .   2
     2.2.  Initial Sieve Action Registry . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Sieve Email Filtering Language [RFC5228] is a popular email
   filtering language used upon final mail delivery.  Popularity  The popularity of
   Sieve resulted in a myriad of Sieve extensions that can interact with
   each other in wonderful and complex ways.  There  Currently, there is currently no
   easy way to find out all actions defined by Sieve extensions
   published in RFCs, which
   make makes it quite difficult for Sieve extension
   writers and Sieve implementation developers to forsee foresee interactions
   between Sieve actions.

   This document creates a registry of for Sieve [RFC5228] actions in order
   to help developers and Sieve extension writers track interactions
   between different extensions.

2.  IANA Considerations

2.1.  Sieve Actions Registration Template and Procedure

   IANA is requested to create a new has created the "Sieve Actions" registry for Sieve actions (see Section 2.9 of
   [RFC5228] for details on Sieve actions).  Registration of both actions
   specified in IETF Stream both RFCs and vendor specific
   actions vendor-specific documentation is allowed
   and encouraged.  The registration template
   contains:

   1.  name contains the following:

   Name:  Name of the action;

   2.  short description;

   3.  references: one action
   Description:  Short description
   References:  One or more documents describing the action and any
      significant updates to its definition (this field is required for
      actions described in RFCs and is optional otherwise);

   4.  name(s) otherwise)
   Capabilities:  Name of one or more Sieve capabilit(ies) capabilities associated with
      the Sieve action being registered;
   5.  interactions registered
   Action Interactions:  Interactions with other Sieve actions (as
      described in Section 2.10.1 of [RFC5228]), if any;

   6.  flag any
   Cancels Implicit Keep?  Flag specifying whether the action cancels
      the implicit keep (see Section 2.10.2 of [RFC5228]);

   7.  whether [RFC5228])
   Can Use With IMAP Events?  Whether or not this action can be used
      with IMAP events in Sieve
       ([RFC6785]);

   8.  optional comment.

   Registration [RFC6785]
   Comments:  Optional comment or comments

   The registration procedure for this registry is Expert Review. Review [RFC8126].  The
   Designated Expert
   designated expert only checks that the name of the action being
   registered matches documentation, that the description field is accurate, that
   the correct documents are referenced referenced, and that the list of relevant
   documents is as complete as possible.  The Designated
   Expert can’t designated expert can't
   reject a registration based on because of a personal dislike of for the document
   defining an action and should always err on the side of
   registering, approving the
   registration, even if documentation is not complete.

   Addition of

   The same registration procedure is used to add a new reference to an existing registration or change to
   change the description field goes through the same registration procedure as
   a new of an existing registration.

2.2.  Initial Sieve Action Registry

   The following table is registrations are used to initialize the actions "Sieve
   Actions" registry.  Note that when the relevant "Action Interactions" cell
   entry is empty marked "N/A", it means that there is no restriction on use
   of the corresponding action with any other
   action, however action; however,
   implementors still need to read the one or more corresponding
   specification(s)
   specifications to see determine if there is are any surprising behaviour. behaviors.
   Also note that the "Comments" field of the IANA registration template
   is omitted from this table, these registrations, as no registration none of them currently have
   any
   comment.

   +============+=============+==========+==============+============+========+=======+
   |Name        |Description  |References|Capabilities  |Action      |Cancels |Can use|
   |            |             |          |              |Interactions|Implicit|with   |
   |            |             |          |              |            |Keep?   |IMAP   |
   |            |             |          |              |            |        |Events?|
   +============+=============+==========+==============+============+========+=======+
   |addheader   |Add comments.

   Name:  addheader
   Description:  Add a header |[RFC5293] |"editheader"  |All         |No      |Yes    |
   |            |field to the |          |              |subsequent  |        |       |
   |            |existing     |          |              |tests and   |        |       |
   |            |message      |          |              |actions     |        |       |
   |            |header       |          |              |apply to the|        |       |
   |            |             |          |              |altered     |        |       |
   |            |             |          |              |message     |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |addflag     |Add IMAP     |[RFC5232],|"imap4flags", |            |No      |Yes    |
   |            |flags to a   |[RFC5229] |"variables"   |            |        |       |
   |            |list of IMAP |          |              |            |        |       |
   |            |flags field to the existing message header
   References:  [RFC5293]
   Capabilities:  "editheader"
   Action Interactions:  All subsequent tests and actions apply to the
      altered message
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  addflag
   Description:  Add IMAP flags to a list of IMAP flags that   |          |              |            |        |       |
   |            |would would be
      set |          |              |            |        |       |
   |            |on the       |          |              |            |        |       |
   |            |message on the message if it|          |              |            |        |       |
   |            |gets         |          |              |            |        |       |
   |            |delivered to |          |              |            |        |       |
   |            |a it gets delivered to a mailbox    |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |convert     |Convert
   References:  [RFC5232] [RFC5229]
   Capabilities:  "imap4flags", "variables"
   Action Interactions:  N/A
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  convert
   Description:  Convert body |[RFC6558] |"convert"     |All         |No      |Yes    |
   |            |parts parts from   |          |              |subsequent  |        |       |
   |            |one one MIME type|          |              |tests and   |        |       |
   |            |to type to another   |          |              |actions     |        |       |
   |            |             |          |              |apply to the|        |       |
   |            |             |          |              |altered     |        |       |
   |            |             |          |              |message     |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |deleteheader|Remove a     |[RFC5293] |"editheader"  |All         |No      |Yes    |
   |            |header
   References:  [RFC6558]
   Capabilities:  "convert"
   Action Interactions:  All subsequent tests and actions apply to the
      altered message
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  deleteheader
   Description:  Remove a header field |          |              |subsequent  |        |       |
   |            |from the     |          |              |tests and   |        |       |
   |            |existing     |          |              |actions     |        |       |
   |            |message      |          |              |apply to the|        |       |
   |            |header       |          |              |altered     |        |       |
   |            |             |          |              |message     |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |discard     |Silently     |[RFC5228] |              |            |Yes     |Yes    |
   |            |throw from the existing message header
   References:  [RFC5293]
   Capabilities:  "editheader"
   Action Interactions:  All subsequent tests and actions apply to the
      altered message
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  discard
   Description:  Silently throw away   |          |              |            |        |       |
   |            |the the message
   References:  [RFC5228]
   Capabilities:  N/A
   Action Interactions:  N/A
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  Yes

   Name:  enclose
   Description:  Enclose a message  |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |enclose     |Enclose a    |[RFC5703] |"enclose"     |All         |No      |Yes    |
   |            |message as an|          |              |subsequent  |        |       |
   |            |attachment to|          |              |tests and   |        |       |
   |            |a an attachment to a new message|          |              |actions,    |        |       |
   |            |             |          |              |except      |        |       |
   |            |             |          |              |"redirect"  |        |       |
   |            |             |          |              |apply to the|        |       |
   |            |             |          |              |altered     |        |       |
   |            |             |          |              |message     |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |ereject     |Refuse       |[RFC5429] |"ereject"     |Incompatible|Yes     |No     |
   |            |delivery of  |          |              |with        |        |       |
   |            |the message  |          |              |"vacation"  |        |       |
   |            |             |          |              |action.     |        |       |
   |            |             |          |              |Typically is|        |       |
   |            |             |          |              |not         |        |       |
   |            |             |          |              |permitted   |        |       |
   |            |             |          |              |with actions|        |       |
   |            |             |          |              |that
   References:  [RFC5703]
   Capabilities:  "enclose"
   Action Interactions:  All subsequent tests and actions except
      "redirect" apply to the altered message
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  ereject
   Description:  Refuse delivery of the message
   References:  [RFC5429]
   Capabilities:  "ereject"
   Action Interactions:  This action is incompatible with the "vacation"
      action.  Typically is not permitted with actions that cause  |        |       |
   |            |             |          |              |mail        |        |       |
   |            |             |          |              |delivery,   |        |       |
   |            |             |          |              |such mail
      delivery, such as     |        |       |
   |            |             |          |              |"keep",     |        |       |
   |            |             |          |              |"fileinto", |        |       |
   |            |             |          |              |and         |        |       |
   |            |             |          |              |"redirect". |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |extracttext |Store "keep", "fileinto", and "redirect"
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  No

   Name:  extracttext
   Description:  Store text of|[RFC5703],|"extracttext",|            |No      |Yes    |
   |            |a of a MIME part  |[RFC5229] |"variables"   |            |        |       |
   |            |into a       |          |              |            |        |       |
   |            |variable     |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |fileinto    |Deliver the  |[RFC5228],|"fileinto",   |Use of :copy|Yes     |Yes    |
   |            |message into |[RFC3894],|"copy",       |suppresses  |        |       |
   |            |the specified|[RFC5232],|"imap4flags", |cancelation |        |       |
   |            |mailbox      |[RFC5490],|"mailbox",    |of a variable
   References:  [RFC5703] [RFC5229]
   Capabilities:  "extracttext", "variables"
   Action Interactions:  N/A
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  fileinto
   Description:  Deliver the message into the specified mailbox
   References:  [RFC5228] [RFC3894] [RFC5232] [RFC5490] [RFC9042]
      [RFC8579]
   Capabilities:  "fileinto", "copy", "imap4flags", "mailbox",
      "mailboxid", "special-use"
   Action Interactions:  Use of :copy suppresses cancellation of
      implicit |        |       |
   |            |             |[RFC9042],|"mailboxid",  |keep        |        |       |
   |            |             |[RFC8579] |"special-use" |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |keep        |File keep
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  Yes

   Name:  keep
   Description:  File the message |[RFC5228],|"imap4flags"  |            |Yes     |Yes    |
   |            |into the     |[RFC5232] |              |            |        |       |
   |            |user's into the user's main  |          |              |            |        |       |
   |            |mailbox      |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |notify      |Send a       |[RFC5435],|"enotify",    |            |No      |Yes    |
   |            |notification |[RFC8580] |"fcc"         |            |        |       |
   |            |to mailbox
   References:  [RFC5228] [RFC5232]
   Capabilities:  "imap4flags"
   Action Interactions:  N/A
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  Yes

   Name:  notify
   Description:  Send a notification to a user    |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |redirect    |Send         |[RFC5228],|"copy",       |Use of :copy|Yes     |Yes    |
   |            |(forward) the|[RFC3894],|"redirect-    |suppresses  |        |       |
   |            |message to   |[RFC6009],|dsn",         |cancelation |        |       |
   |            |another
   References:  [RFC5435] [RFC8580]
   Capabilities:  "enotify", "fcc"
   Action Interactions:  N/A
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  redirect
   Description:  Send (forward) the message to another user |[RFC6134] |"redirect-    |of
   References:  [RFC5228] [RFC3894] [RFC6009] [RFC6134]
   Capabilities:  "copy", "redirect-dsn", "redirect-deliverby",
      "extlists"
   Action Interactions:  Use of :copy suppresses cancellation of
      implicit |        |       |
   |            |             |          |deliverby",   |keep        |        |       |
   |            |             |          |"extlists"    |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |reject      |Refuse       |[RFC5429] |"reject"      |Incompatible|Yes     |No     |
   |            |delivery of  |          |              |with        |        |       |
   |            |the keep
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  Yes

   Name:  reject
   Description:  Refuse delivery of the message  |          |              |"vacation"  |        |       |
   |            |             |          |              |action.     |        |       |
   |            |             |          |              |Typically is|        |       |
   |            |             |          |              |not         |        |       |
   |            |             |          |              |permitted   |        |       |
   |            |             |          |              |with actions|        |       |
   |            |             |          |              |that
   References:  [RFC5429]
   Capabilities:  "reject"
   Action Interactions:  This action is incompatible with the "vacation"
      action.  Typically is not permitted with actions that cause  |        |       |
   |            |             |          |              |mail        |        |       |
   |            |             |          |              |delivery,   |        |       |
   |            |             |          |              |such mail
      delivery, such as     |        |       |
   |            |             |          |              |"keep",     |        |       |
   |            |             |          |              |"fileinto", |        |       |
   |            |             |          |              |and         |        |       |
   |            |             |          |              |"redirect". |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |removeflag  |Remove IMAP  |[RFC5232],|"imap4flags", |            |No      |Yes    |
   |            |flags "keep", "fileinto", and "redirect"
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  No

   Name:  removeflag
   Description:  Remove IMAP flags from a |[RFC5229] |"variables"   |            |        |       |
   |            |list of IMAP |          |              |            |        |       |
   |            |flags list of IMAP flags that   |          |              |            |        |       |
   |            |would would
      be set |          |              |            |        |       |
   |            |on the       |          |              |            |        |       |
   |            |message on the message if it|          |              |            |        |       |
   |            |gets         |          |              |            |        |       |
   |            |delivered to |          |              |            |        |       |
   |            |a it gets delivered to a mailbox    |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |replace     |Replace a    |[RFC5703] |"replace"     |All         |No      |Yes    |
   |            |MIME
   References:  [RFC5232] [RFC5229]
   Capabilities:  "imap4flags", "variables"
   Action Interactions:  N/A
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  replace
   Description:  Replace a MIME part    |          |              |subsequent  |        |       |
   |            |             |          |              |tests and   |        |       |
   |            |             |          |              |actions,    |        |       |
   |            |             |          |              |except      |        |       |
   |            |             |          |              |"redirect"  |        |       |
   |            |             |          |              |apply to the|        |       |
   |            |             |          |              |altered     |        |       |
   |            |             |          |              |message     |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |set         |Store a value|[RFC5229] |"variables"   |            |No      |Yes    |
   |            |in a variable|          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |setflag     |Set IMAP     |[RFC5232],|"imap4flags", |            |No      |Yes    |
   |            |system
   References:  [RFC5703]
   Capabilities:  "replace"
   Action Interactions:  All subsequent tests and actions except
      "redirect" apply to the altered message
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  set
   Description:  Store a value in a variable
   References:  [RFC5229]
   Capabilities:  "variables"
   Action Interactions:  N/A
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  setflag
   Description:  Set IMAP system flags |[RFC5229] |"variables"   |            |        |       |
   |            |or or keywords  |          |              |            |        |       |
   |            |that that would be|          |              |            |        |       |
   |            |set be set on
      the   |          |              |            |        |       |
   |            |message message if it|          |              |            |        |       |
   |            |gets         |          |              |            |        |       |
   |            |delivered to |          |              |            |        |       |
   |            |a it gets delivered to a mailbox    |          |              |            |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
   |vacation    |Vacation     |[RFC5230],|"vacation",   |Incompatible|No      |No     |
   |            |autoresponder|[RFC6131],|"vacation-    |with        |        |       |
   |            |             |[RFC8580] |seconds",     |"reject" and|        |       |
   |            |             |          |"fcc"         |"ereject"   |        |       |
   |            |             |          |              |actions.    |        |       |
   +------------+-------------+----------+--------------+------------+--------+-------+
                                  Table 1
   References:  [RFC5232] [RFC5229]
   Capabilities:  "imap4flags", "variables"
   Action Interactions:  N/A
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  Yes

   Name:  vacation
   Description:  Implement a vacation autoresponder
   References:  [RFC5230] [RFC6131] [RFC8580]
   Capabilities:  "vacation", "vacation-seconds", "fcc"
   Action Interactions:  This action is incompatible with "reject" and
      "ereject" actions
   Cancels Implicit Keep?  No
   Can Use with IMAP Events?  No

3.  Security Considerations

   The sole purpose of this document is to create a new IANA registry,
   so the "Sieve Actions"
   registry; therefore, it doesn't create new security considerations
   for Sieve implementations.

   The new registry should help Sieve extension writers and Sieve
   implementors track interactions between different Sieve actions, so actions;
   therefore, it might improve the quality of specifications and
   implementations, including security aspects.

   For the Security Considerations of security considerations related to particular actions, see the RFC(s)
   one or more RFCs referenced for that the action in the Initial Sieve Action Registry question in
   Section 2.2. the "Sieve
   Actions" registry (Section 2.2).

4.  References

4.1.  Normative References

   [RFC5228]  Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
              Filtering Language", RFC 5228, DOI 10.17487/RFC5228,
              January 2008, <https://www.rfc-editor.org/info/rfc5228>.

   [RFC6785]  Leiba, B., "Support for Internet Message Access Protocol
              (IMAP) Events in Sieve", RFC 6785, DOI 10.17487/RFC6785,
              November 2012, <https://www.rfc-editor.org/info/rfc6785>.

4.2.  Informative References

   [RFC3894]  Degener, J., "Sieve Extension: Copying Without Side
              Effects", RFC 3894, DOI 10.17487/RFC3894, October 2004,
              <https://www.rfc-editor.org/info/rfc3894>.

   [RFC5229]  Homme, K., "Sieve Email Filtering: Variables Extension",
              RFC 5229, DOI 10.17487/RFC5229, January 2008,
              <https://www.rfc-editor.org/info/rfc5229>.

   [RFC5230]  Showalter, T. and N. Freed, Ed., "Sieve Email Filtering:
              Vacation Extension", RFC 5230, DOI 10.17487/RFC5230,
              January 2008, <https://www.rfc-editor.org/info/rfc5230>.

   [RFC5232]  Melnikov, A., "Sieve Email Filtering: Imap4flags
              Extension", RFC 5232, DOI 10.17487/RFC5232, January 2008,
              <https://www.rfc-editor.org/info/rfc5232>.

   [RFC5293]  Degener, J. and P. Guenther, "Sieve Email Filtering:
              Editheader Extension", RFC 5293, DOI 10.17487/RFC5293,
              August 2008, <https://www.rfc-editor.org/info/rfc5293>.

   [RFC5429]  Stone, A., Ed., "Sieve Email Filtering: Reject and
              Extended Reject Extensions", RFC 5429,
              DOI 10.17487/RFC5429, March 2009,
              <https://www.rfc-editor.org/info/rfc5429>.

   [RFC5435]  Melnikov, A., Ed., Leiba, B., Ed., Segmuller, W., and T.
              Martin, "Sieve Email Filtering: Extension for
              Notifications", RFC 5435, DOI 10.17487/RFC5435, January
              2009, <https://www.rfc-editor.org/info/rfc5435>.

   [RFC5490]  Melnikov, A., "The Sieve Mail-Filtering Language --
              Extensions for Checking Mailbox Status and Accessing
              Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March
              2009, <https://www.rfc-editor.org/info/rfc5490>.

   [RFC5703]  Hansen, T. and C. Daboo, "Sieve Email Filtering: MIME Part
              Tests, Iteration, Extraction, Replacement, and Enclosure",
              RFC 5703, DOI 10.17487/RFC5703, October 2009,
              <https://www.rfc-editor.org/info/rfc5703>.

   [RFC6009]  Freed, N., "Sieve Email Filtering: Delivery Status
              Notifications and Deliver-By Extensions", RFC 6009,
              DOI 10.17487/RFC6009, October 2010,
              <https://www.rfc-editor.org/info/rfc6009>.

   [RFC6131]  George, R. and B. Leiba, "Sieve Vacation Extension:
              "Seconds" Parameter", RFC 6131, DOI 10.17487/RFC6131, July
              2011, <https://www.rfc-editor.org/info/rfc6131>.

   [RFC6134]  Melnikov, A. and B. Leiba, "Sieve Extension: Externally
              Stored Lists", RFC 6134, DOI 10.17487/RFC6134, July 2011,
              <https://www.rfc-editor.org/info/rfc6134>.

   [RFC6558]  Melnikov, A., Leiba, B., and K. Li, "Sieve Extension for
              Converting Messages before Delivery", RFC 6558,
              DOI 10.17487/RFC6558, March 2012,
              <https://www.rfc-editor.org/info/rfc6558>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8579]  Bosch, S., "Sieve Email Filtering: Delivering to Special-
              Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019,
              <https://www.rfc-editor.org/info/rfc8579>.

   [RFC8580]  Murchison, K. and B. Gondwana, "Sieve Extension: File
              Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May
              2019, <https://www.rfc-editor.org/info/rfc8580>.

   [RFC9042]  Gondwana, B., Ed., "Sieve Email Filtering: Delivery by
              MAILBOXID", RFC 9042, DOI 10.17487/RFC9042, June 2021,
              <https://www.rfc-editor.org/info/rfc9042>.

Appendix A.  Acknowledgements

   TBD.

   Thank you to Barry Leiba, Donald Eastlake, Yoshiro Yoneya, and Murray
   Kucherawy for reviews and feedback on this document.

Authors' Addresses

   Alexey Melnikov
   Isode Ltd
   14 Castle Mews
   Hampton
   TW12 2NP
   United Kingdom
   Email: Alexey.Melnikov@isode.com

   Kenneth Murchison
   Fastmail US LLC
   Suite 1201
   1429 Walnut Street - Suite 1201
   Philadelphia, PA 19102
   United States of America
   Email: murch@fastmailteam.com