IMAP UIDBATCHES Extension
draft-ietf-mailmaint-imap-uidbatches-22

[Ballot comment]
Thanks for the work done in this document. Some non-blocking COMMENTs below

### Abstract

In which units are the batches defined ? Messages ? Lines ? Bytes ? Same comment for section 1.

### Use of SHOULD

Why not a MUST in `The server SHOULD reject UIDBATCHES commands with a NO response` in section 3.1.1 ? See also https://datatracker.ietf.org/doc/statement-iesg-statement-on-clarifying-the-use-of-bcp-14-key-words/

Same comment about `Servers SHOULD return batches close to the requested size (>= 90% when possible)` in section 3.1.3.1. or `When operating in UIDONLY mode, clients SHOULD use UIDBATCHES to determine appropriate UID ranges` in section 3.3.

Note that section 3.1.3.3. has the additional guidance when using SHOULD ;-)

[Ballot comment]
Hi Daniel,

Thank you for the effort put into this document.

Please find below some comments, fwiw:

# MUST NOT …exception

CURRENT:
  To prevent server overload, the client MUST NOT resend UIDBATCHES
  unless at least one of the following conditions is met:

I think this should be:

NEW:
  To prevent server overload, the client SHOULD NOT resend UIDBATCHES
  unless at least one of the following conditions is met:


Per RFC2119:

2. MUST NOT  This phrase, or the phrase "SHALL NOT", mean that the
  definition is an absolute prohibition of the specification.

# Limit

CURRENT:
  Clients MUST request at least 500 messages per batch

What is the rationale for setting that limit?

# Batch size

CURRENT:
  The server MUST support batch sizes of 500 messages or larger. 

and

  The server MUST respond with NO and a response code TOOFEW if the
  client uses a batch size smaller than the minimum allowed by the
  server:

The server may support so, but is the intent that lower values are discarded by default? For example, can a configuration parameter be provided by a server implementation to supply a value lower than 500 as an acceptable value? Or that should be discarded by design?

# Efficient implementations

CURRENT:
  While servers SHOULD ideally return batches that correspond exactly
  to the requested size, they have flexibility in specific
  circumstances to enable efficient implementations.

Efficient implementations/behavior may rely on testing/evaluation to craft an optimized size value, not only hardcoded in the implem.

## The above requirement can be satisfied if server operators are not provided with a knob to control that behavior. Can we say so explicitly in the Operational Considerations section (Section 5)?

## A companion aspect is whether for a server to expose which bounds it actually supports. This can be used by management systems.

## I would delete “ideally”.

# Substantially simpler

CURRENT:
  1.  When doing so makes the implementation substantially simpler and/
      or more efficient

How to characterize that?

How is this different from saying that servers are free to ignore it (i.e., with having a condition on something that can’t be easily enforced/checked)?

# No need to repeat IANA policy

CURRENT:

  IMAP4 capabilities are registered by publishing a standards track or
  IESG approved Informational or Experimental RFC. 

  …

  IMAP4 response codes are registered by publishing a standards track
  or IESG approved Informational or Experimental RFC. 

I would delete these sentences.

# Nits

## 3.1.3.1

OLD: The following tables provide

NEW1: The following table provides

or

NEW2: Table 1 provides

## 3.1.5

OLD: See section Section 3.1.6.

NEW: See Section 3.1.6.

Cheers,
Med

IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-mailmaint-imap-uidbatches-20. If any part of this review is inaccurate, please let us know.

IANA understands that, upon approval of this document, there are two actions which we must complete.

First, in the IMAP Capabilities registry in the Internet Message Access Protocol (IMAP) Capabilities Registry group located at:

https://www.iana.org/assignments/imap-capabilities/

a single new registration will be made as follows:

Capability Name: UIDBATCHES
Reference: [ RFC-to-be ]

Second, in the IMAP Response Codes registry located at:

https://www.iana.org/assignments/imap-response-codes/

two new registrations will be made as follows:

Response Code: TOOMANY
Reference: [ RFC-to-be ]
Status Description:

Response Code: TOOFEW
Reference: [ RFC-to-be ]
Status Description:

As this document requests registrations in an Expert Review or Specification Required (see RFC 8126) registry, we will initiate the required Expert Review via a separate request. This review must be completed before the document's IANA state can be changed to "IANA OK."

We understand that these are the only actions required to be completed upon approval of this document.

NOTE: The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the list of actions that will be performed.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2026-01-09):

From: The IESG
To: IETF-Announce
CC: andy@hxr.us, draft-ietf-mailmaint-imap-uidbatches@ietf.org, mailmaint-chairs@ietf.org, mailmaint@ietf.org, murch@fastmail.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (IMAP UIDBATCHES Extension) to Proposed Standard


The IESG has received a request from the Mail Maintenance WG (mailmaint) to
consider the following document: - 'IMAP UIDBATCHES Extension'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2026-01-09. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  The UIDBATCHES extension of the Internet Message Access Protocol
  (IMAP) allows clients to retrieve UID ranges that partition a
  mailbox's messages into equally sized batches.  This enables clients
  to perform operations such as FETCH, SEARCH, and STORE on specific
  message batches, providing better control over resource usage and
  response sizes.  The extension is particularly useful with the
  UIDONLY mode where sequence numbers are unavailable.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-mailmaint-imap-uidbatches/



No IPR declarations have been submitted directly on this I-D.


The document contains these normative downward references.
See RFC 3967 for additional information:
    rfc9738: IMAP MESSAGELIMIT Extension (Experimental - Internet Engineering Task Force (IETF) stream)

Ken confirmed -19 is ready.

In reviewing nits, the following shows up:

  ** Obsolete normative reference: RFC 3501 (Obsoleted by RFC 9051)
  ** Downref: Normative reference to an Experimental RFC: RFC 9586
  ** Downref: Normative reference to an Experimental RFC: RFC 9738

I have asked that the RFC 9586 be moved to an informative reference. The text of the draft adequately handles RFC 3501, and the reference to RFC 9738 will need to go to the downref registry as the normative reference is about co-existence with RFC 9738 but is not required to implement this specification otherwise.

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

Thank you for your service as a document shepherd. Among the responsibilities is
answering the questions in this write-up to give helpful context to Last Call
and Internet Engineering Steering Group ([IESG][1]) reviewers, and your
diligence in completing it is appreciated. The full role of the shepherd is
further described in [RFC 4858][2]. You will need the cooperation of the authors
and editors to complete these checks.

Note that some numbered items contain multiple related questions; please be sure
to answer all of them.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

There was strong concurrence among those that actually implemented
the protocol.  Others in the group saw value in the protocol and were in
favor of moving the document forward based on the implementation and
interoperation results.  There was no opposition to the document.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No.  There was no controversy on the technical aspects of the protocol.
The main discussion points were about text regarding range sizes and
how to make that text sane and unambiguous.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

There are at least three known implementations of this protocol:
      - Apple iOS Mail client
      - iCloud IMAP Server
      - Cyrus IMAP Server (used in production at Fastmail)

The Apple client has proven to be interoperable in production with both server
implementations for several weeks.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No.  This document is a simple IMAP extension and this WG has
sufficient expertise in this area.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

NA.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

NA.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

The ABNF has been validated using the BAP tool.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

The ART issues list has been reviewed and the only categories that are
applicable to this document are Email protocol (IMAP) and ABNF.  The
WG has sufficient expertise in IMAP and has approved the document.
The ABNF has been validated with the BAP tool.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Proposed Standard.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

Yes.  The author has verified via email that there are no IPR claims
by he or his employer.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

- The missing references nits are bogus.  Those are IMAP protocol elements.
- Normative reference to the obsoleted RFC 3501, but the current RFC 9051
  is also referenced because this extension can be used with BOTH
  IMAP4rev1 and IMAP3rev2.
- Downref to RFC 9738 (see #17 below)

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

NA.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

This document (UIDBATCHES) normatively references Experimental RFC 9738
(MESSAGELIMIT) in the context of how a UIDBATCHES client should
behave if the server also supports the MESSAGELIMIT extension.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

The IANA Considerations are complete and correct.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

NA.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

Thank you for your service as a document shepherd. Among the responsibilities is
answering the questions in this write-up to give helpful context to Last Call
and Internet Engineering Steering Group ([IESG][1]) reviewers, and your
diligence in completing it is appreciated. The full role of the shepherd is
further described in [RFC 4858][2]. You will need the cooperation of the authors
and editors to complete these checks.

Note that some numbered items contain multiple related questions; please be sure
to answer all of them.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

There was strong concurrence among those that actually implemented
the protocol.  Others in the group saw value in the protocol and were in
favor of moving the document forward based on the implementation and
interoperation results.  There was no opposition to the document.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No.  There was no controversy on the technical aspects of the protocol.
The main discussion points were about text regarding range sizes and
how to make that text sane and unambiguous.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

There are at least three known implementations of this protocol:
      - Apple iOS Mail client
      - iCloud IMAP Server
      - Cyrus IMAP Server (used in production at Fastmail)

The Apple client has proven to be interoperable in production with both server
implementations for several weeks.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No.  This document is a simple IMAP extension and this WG has
sufficient expertise in this area.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

NA.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

NA.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

The ABNF has been validated using the BAP tool.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

The ART issues list has been reviewed and the only categories that are
applicable to this document are Email protocol (IMAP) and ABNF.  The
WG has sufficient expertise in IMAP and has approved the document.
The ABNF has been validated with the BAP tool.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Proposed Standard.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

Yes.  The author has verified via email that there are no IPR claims
by he or his employer.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

- The missing references nits are bogus.  Those are IMAP protocol elements.
- Normative reference to the obsoleted RFC 3501, but the current RFC 9051
  is also referenced because this extension can be used with BOTH
  IMAP4rev1 and IMAP3rev2.
- Downref to RFC 9738 (see #17 below)

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

NA.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

This document (UIDBATCHES) normatively references Experimental RFC 9738
(MESSAGELIMIT) in the context of how a UIDBATCHES client should
behave if the server also supports the MESSAGELIMIT extension.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

The IANA Considerations are complete and correct.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

NA.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/