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Internet Engineering Task Force (IETF)                       A. Melnikov
Request for Comments: 9122                                     Isode Ltd
Category: Standards Track                                   K. Murchison
ISSN: 2070-1721                                                 Fastmail
                                                               June 2023

IANA Registry for Sieve 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 for Sieve actions to help developers and Sieve extension writers track interactions between different extensions.

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/rfc9122.

Copyright Notice

Copyright © 2023 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.

Table of Contents

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

1. Introduction

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

This document creates a registry 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 has created the "Sieve Actions" registry (see Section 2.9 of [RFC5228] for details on Sieve actions). Registration of actions specified in both RFCs and vendor-specific documentation is allowed and encouraged. The registration template contains the following: 

   Name:  Name of the 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)
   Capabilities:  Name of one or more Sieve capabilities associated with
      the Sieve action being registered
   Action Interactions:  Interactions with other Sieve actions (as
      described in Section 2.10.1 of [RFC5228]), if any
   Cancels Implicit Keep?  Flag specifying whether the action cancels
      the implicit keep (see Section 2.10.2 of [RFC5228])
   Can Use With IMAP Events?  Whether or not this action can be used
      with IMAP events in Sieve [RFC6785]
   Comments:  Optional comment or comments

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

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

2.2. Initial Sieve Action Registry

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

   Name:  addheader
   Description:  Add a header 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 be
      set on the message if it gets delivered to a mailbox
   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 parts from one MIME type to another
   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 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 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 as an attachment to a new message
   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 as "keep", "fileinto", and "redirect"
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  No
   
   Name:  extracttext
   Description:  Store text of a MIME part into 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 keep
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  Yes
   
   Name:  keep
   Description:  File the message into the user's main 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
   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
   References:  [RFC5228] [RFC3894] [RFC6009] [RFC6134]
   Capabilities:  "copy", "redirect-dsn", "redirect-deliverby",
      "extlists"
   Action Interactions:  Use of :copy suppresses cancellation of
      implicit keep
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  Yes
   
   Name:  reject
   Description:  Refuse delivery of the message
   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 as "keep", "fileinto", and "redirect"
   Cancels Implicit Keep?  Yes
   Can Use with IMAP Events?  No
   
   Name:  removeflag
   Description:  Remove IMAP flags from a list of IMAP flags that would
      be set on the message if it gets delivered to a mailbox
   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
   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 or keywords that would be set on
      the message if it gets delivered to a mailbox
   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 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; therefore, it might improve the quality of specifications and implementations, including security aspects.

For security considerations related to particular actions, see the one or more RFCs referenced for the action in question in 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

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
Philadelphia, PA 19102
United States of America
Email: murch@fastmailteam.com