As required by RFC 4858, this is the current template for the Document
Changes are expected over time. This version is dated 24 February 2012.
(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)? Why
is this the proper type of RFC? Is this type of RFC indicated in the
title page header?
Proposed Standard as indicated on the title page header and in the
(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:
SMTP Mail Transfer Agent Strict Transport Security (MTA-STS) is a
mechanism enabling mail service providers to declare their ability to
receive Transport Layer Security (TLS) secure SMTP connections, and
to specify whether sending SMTP servers should refuse to deliver to
MX hosts that do not offer TLS with a trusted server certificate.
Working Group Summary
The WG had a hard time aligning on the format of MTA-STS policy
and initially had chosen JSON as the format. Strong push-back from
parts of the opensource community led to a change to key-value text
based format. The consensus is strong on the new format but the path
there was a bit rough. There is still too little understanding of
how SNI is deployed in the email domain to warrant clear normative
language on the use of SNI. Security directorate review may change
this a bit but probably not much. The WG consensus is to leave the
language as is in the draft.
There are multiple implementations on the protocol and major email-
providers (eg google) are already deploying the protocol as specified.
There are indications that major opensource implementations of MTAs
will implement the protocol.
Who is the Document Shepherd? Who is the Responsible Area
Leif Johansson (shep)
Alexei Melnikov (AD)
(3) Briefly describe the review of this document that was performed by
the Document Shepherd. If this version of the document is not ready
for publication, please explain why the document is being forwarded to
I have reviewed the document and find it ready. A second shepheard
review is under way by the co-chair.
(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?
None. There has been signifficant review by implementors and by
other members of the WG.
(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
No but an expert ABNF review would be useful.
(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
See note about SNI above.
(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.
Yes. IPR has already been filed against the document by Yahoo.
(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
The WG has not discussed the IPR disclosure which grants "Royalty-Free,
Reasonable and Non-Discriminatory License to All Implementers". The
IPR disclosure lacks a link/info about the patent (no patent details).
I don't know if this is cause for concern though.
(9) How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?
The WG consensus is strong at this point (cf note about JSON
(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise 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.)
(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
Minor warnings only. Authors will address in final revision.
(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.
None are applicable as far as I can see but an ABNF review
would be useful.
(13) Have all references within this document been identified as
either normative or informative?
(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?
(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in
the Last Call procedure.
(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.
(17) 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 protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).
Two new registry is created ("STS Policy Fields" and "MTA STS TXT
Record Fields"). The registries are created using the expert review
policy and is consistent with the document and clearly defined.
One item is registered in the .well-known URI registry. The requirements
for that registry are fulfilled.
(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.
"STS Policy Fields" and "MTA STS TXT Record Fields"
Pick experts that have a solid history and knowledge about email
deployment. One possible name is Viktor Dukhovni <firstname.lastname@example.org>
(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.
Bill Fenners ABNF checker shows no errors on the MTA-STS policy format