< draft-ietf-emailcore-as-01.txt		draft-ietf-emailcore-as-02.txt >
	EMAILCORE J. Klensin, Ed.		EMAILCORE J. Klensin, Ed.
	Internet-Draft		Internet-Draft
	Intended status: Standards Track K. Murchison		Intended status: Standards Track K. Murchison
	Expires: October 11, 2021 Fastmail		Expires: January 12, 2022 Fastmail
	E. Sam		E. Sam
	April 9, 2021		July 11, 2021
	Applicability Statement for IETF Core Email Protocols		Applicability Statement for IETF Core Email Protocols
	draft-ietf-emailcore-as-01		draft-ietf-emailcore-as-02
	Abstract		Abstract
	Electronic mail is one of the oldest Internet applications that is		Electronic mail is one of the oldest Internet applications that is
	still in very active use. While the basic protocols and formats for		still in very active use. While the basic protocols and formats for
	mail transport and message formats have evolved slowly over the		mail transport and message formats have evolved slowly over the
	years, events and thinking in more recent years have supplemented		years, events and thinking in more recent years have supplemented
	those core protocols with additional features and suggestions for		those core protocols with additional features and suggestions for
	their use. This Applicability Statement describes the relationship		their use. This Applicability Statement describes the relationship
	among many of those protocols and provides guidance and makes		among many of those protocols and provides guidance and makes
	skipping to change at page 1, line 45 ¶		skipping to change at page 1, line 45 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on October 11, 2021.		This Internet-Draft will expire on January 12, 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 25 ¶		skipping to change at page 2, line 25 ¶
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Applicability of Some SMTP Provisions . . . . . . . . . . . . 3		2. Applicability of Some SMTP Provisions . . . . . . . . . . . . 3
	3. Applicability of Message Format Provisions . . . . . . . . . 3		3. Applicability of Message Format Provisions . . . . . . . . . 3
	4. MIME and Its Implications . . . . . . . . . . . . . . . . . . 4		4. Use of IP addresses/domain names in EHLO . . . . . . . . . . 4
	5. Other Stuff . . . . . . . . . . . . . . . . . . . . . . . . . 4		5. Extension Keywords Starting in X- . . . . . . . . . . . . . . 4
	6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4		6. IP address literals in EHLO . . . . . . . . . . . . . . . . . 4
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		7. Use of empty quote strings in email messages . . . . . . . . 5
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 4		8. MIME and Its Implications . . . . . . . . . . . . . . . . . . 5
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		9. Other Stuff . . . . . . . . . . . . . . . . . . . . . . . . . 6
	9.1. Normative References . . . . . . . . . . . . . . . . . . 5		10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
	9.2. Informative References . . . . . . . . . . . . . . . . . 5		11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 6		12. Security Considerations . . . . . . . . . . . . . . . . . . . 6
			13. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
			13.1. Normative References . . . . . . . . . . . . . . . . . . 6
			13.2. Informative References . . . . . . . . . . . . . . . . . 7
			Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 8
	A.1. Changes from draft-klensin-email-core-as-00 (2020-03-30)		A.1. Changes from draft-klensin-email-core-as-00 (2020-03-30)
	to draft-ietf-emailcore-as-00 . . . . . . . . . . . . 6		to draft-ietf-emailcore-as-00 . . . . . . . . . . . . 8
	A.2. Changes from draft-ietf-emailcore-as-00 (2020-10-06) to		A.2. Changes from draft-ietf-emailcore-as-00 (2020-10-06) to
	-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . 6		-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6		A.3. Changes from draft-ietf-emailcore-as-01 (2021-04-09) to
			-02 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	In its current form, this draft is a placeholder and beginning of an		In its current form, this draft is a placeholder and beginning of an
	outline for the Applicability Statement that has been discussed as a		outline for the Applicability Statement that has been discussed as a
	complement for proposed revisions of the base protocol specifications		complement for proposed revisions of the base protocol specifications
	for SMTP [RFC5321] (being revised as ID.RFC5321bis [ID.RFC5321bis])		for SMTP [RFC5321] (being revised as ID.RFC5321bis [ID.RFC5321bis])
	and Internet Message Format [RFC5322] (being revised as ID.RFC5322bis		and Internet Message Format [RFC5322] (being revised as ID.RFC5322bis
	[ID.RFC5322bis]). Among other things, it is expected to capture		[ID.RFC5322bis]). Among other things, it is expected to capture
	topics that a potential WG concludes are important but that should		topics that a potential WG concludes are important but that should
	not become part of those core documents.		not become part of those core documents.
	As discussed in RFC 2026 [RFC2026],		As discussed in RFC 2026 [RFC2026],
	"An Applicability Statement specifies how, and under what		"An Applicability Statement specifies how, and under what
	circumstances, one or more TSs may be applied to support a		circumstances, one or more TSs may be applied to support a
	particular Internet capability."		particular Internet capability."
	That form of a standards track document is appropriate because one of		That form of a standards track document is appropriate because one of
	the roles of such a document is to explain the relationship among		the roles of such a document is to explain the relationship among
	technical specification, describe how they are used together, and		technical specification, describe how they are used together, and
	make statements about what is "required, recommended, or elective".		make statements about what is "required, recommended, or elective".
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	skipping to change at page 4, line 5 ¶		skipping to change at page 4, line 7 ¶
	]]		]]
	3. Applicability of Message Format Provisions		3. Applicability of Message Format Provisions
	Placeholder:		Placeholder:
	I am not sure what, if anything, goes here. If nothing does, we drop		I am not sure what, if anything, goes here. If nothing does, we drop
	the section.		the section.
	[[CREF2: ... Actual content to be supplied after WG consideration.]]		[[CREF2: ... Actual content to be supplied after WG consideration.]]
	4. MIME and Its Implications		4. Use of IP addresses/domain names in EHLO
			There has been a suggestion to update RFC 5321 [RFC5321] to clarify
			that servers may verify the domain name in the EHLO command to see if
			it matches up with the IP address of the client. The reasoning
			behind this was that many mail servers were already verifying the
			domain name provided with the EHLO command for anti spam purposes,
			and that mail servers that don't have a matching domain name/IP
			address are more likely to have their mail rejected.
			People for this change say that this is the "de facto" practice and
			that it should be formally specified since basically all mail servers
			are verifying the EHLO domain name anyway.
			People against this argue that the domain names supplied with the
			EHLO command won't always have a matching IP because they are
			internal domain names or a custom domain convention.
			The consensus was that this should be specified within RFC 5231 due
			to the fact it is already taking place to prevent spam.
			5. Extension Keywords Starting in X-
			Since the release of the SMTP RFC, opinons on "X" extensions have
			changed over the years. These opinions can best be represented by
			RFC 6648 [RFC6648]. In short, people are beginning to "shy away"
			from the usage of "X" extensions.
			The proposed changes would involve the removal of the "X" extension
			provisions in Section 2.2.2 of the SMTP RFC, and also called for the
			removal of how to deal with "X" extensinos in the IANA considerations
			and private-use commands.
			While the exact solution is being talked about, the general consensus
			is that its a good idea for this part of the RFC to be removed or
			reformed.
			6. IP address literals in EHLO
			One of the proposed ideas on the mailing list was to clarify if IP
			addresses are allowed to be used as a EHLO parameter. While the
			original specification allowed for the use of IP addresses instead of
			a domain name, it didn't say if the mail server was required to
			accept IP addresses
			The people that suggest that the specification should not require IP
			addresses to be accepted say that anti-spam systems already reject
			emails with IP addresses in EHLO commands, just like how they reject
			domain names that don't match up with a valid IP.
			However, some say there are some valid use cases for EHLO commands to
			have IP literals, for example in private networks.
			The general opinion is that the specification should have a section
			explaining why IP addresses are not recommended as an EHLO parameter,
			but should not ban IP literals outright.
			7. Use of empty quote strings in email messages
			quoted-string ABNF non terminal is used in various places in
			rfc5322bis grammar. While it allows for empty quoted string, such
			construct is going to cause interoperability issues when used in
			certain header fields. In particular, use of empty quoted strings is
			NOT RECOMMENDED in "received-token" (a component of a Received header
			field), "keywords" (a component of a Keywords header field) and
			"local-part" (left hand side of email addresses). Use of empty
			quoted strings is in particular problematic in the "local-part". For
			example, all of the following email addresses are non interoperable:
			"".bar@example.com
			foo.""@example.net
			""@example.com
			Use of empty quoted strings is fine in "display-name".
			8. MIME and Its Implications
	When the work leading to the original version of the MIME		When the work leading to the original version of the MIME
	specification was completed in 1992 [RFC1341], the intention was that		specification was completed in 1992 [RFC1341], the intention was that
	it be kept separate from the specification for basic mail headers in		it be kept separate from the specification for basic mail headers in
	RFC 822 [RFC0822]. That plan was carried forward into RFC 822's		RFC 822 [RFC0822]. That plan was carried forward into RFC 822's
	successors, RFC 2822 [RFC2822] and RFC 5322 [RFC5322] and the		successors, RFC 2822 [RFC2822] and RFC 5322 [RFC5322] and the
	successors of that original MIME specification including RFC 2045		successors of that original MIME specification including RFC 2045
	[RFC2045]. The decision to do so was different from the one made for		[RFC2045]. The decision to do so was different from the one made for
	SMTP, for which the core specification was changed to allow for the		SMTP, for which the core specification was changed to allow for the
	extension mechanism [RFC1425] which was then incorporated into RFC		extension mechanism [RFC1425] which was then incorporated into RFC
	5321 and its predecessor [RFC2821].		5321 and its predecessor [RFC2821].
	Various uses of MIME have become nearly ubiquitous in contemporary		Various uses of MIME have become nearly ubiquitous in contemporary
	email while others may have fallen into disuse or been repurposed		email while others may have fallen into disuse or been repurposed
	from the intent of their original design.		from the intent of their original design.
	It may be appropriate to make some clear statements about the		It may be appropriate to make some clear statements about the
	applicability of MIME and its features.		applicability of MIME and its features.
	5. Other Stuff		9. Other Stuff
	It is fairly clear that there will be things that do not fit into the		It is fairly clear that there will be things that do not fit into the
	sections outlined above. As one example, if the IETF wants to say		sections outlined above. As one example, if the IETF wants to say
	something specific about signatures over headers or what (non-trace)		something specific about signatures over headers or what (non-trace)
	headers may reasonably be altered in transit, that may be more		headers may reasonably be altered in transit, that may be more
	appropriate to other sections than to any of the three suggested		appropriate to other sections than to any of the three suggested
	above.		above.
	6. Acknowledgments		10. Acknowledgments
	... To be supplied...		The Emailcore group arose out of discussions on the ietf-smtp group
	[[CREF3: But don't forget to mention the discussions on the SMTP list		over changes and additions that should be made to the core email
	of the reasons for this document in the last half of 2019. ]]		protocols. It was agreed upon that it was time to create a working
			group that would fix many potential errors and opportunities for
			misunderstandings within the RFCs
	7. IANA Considerations		11. IANA Considerations
	This memo includes no requests to or actions for IANA. The IANA		This memo includes no requests to or actions for IANA. The IANA
	registries associated with the protocol specifications it references		registries associated with the protocol specifications it references
	are specified in their respective documents.		are specified in their respective documents.
	8. Security Considerations		12. Security Considerations
	All drafts are required to have a security considerations section and		All drafts are required to have a security considerations section and
	this one eventually will.		this one eventually will.
	... To be supplied ...		... To be supplied ...
	9. References		13. References
	9.1. Normative References		13.1. Normative References
	[RFC2026] Bradner, S., "The Internet Standards Process -- Revision		[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
	3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,		3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,
	<https://www.rfc-editor.org/info/rfc2026>.		<https://www.rfc-editor.org/info/rfc2026>.
	[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail		[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
	Extensions (MIME) Part One: Format of Internet Message		Extensions (MIME) Part One: Format of Internet Message
	Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,		Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
	<https://www.rfc-editor.org/info/rfc2045>.		<https://www.rfc-editor.org/info/rfc2045>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	9.2. Informative References		13.2. Informative References
	[ID.RFC5321bis]		[ID.RFC5321bis]
	Klensin, J., "Simple Mail Transfer Protocol", Feburary		Klensin, J., "Simple Mail Transfer Protocol", Feburary
	2021, <https://datatracker.ietf.org/doc/draft-klensin-		2021, <https://datatracker.ietf.org/doc/draft-klensin-
	rfc5321bis/>.		rfc5321bis/>.
	[ID.RFC5322bis]		[ID.RFC5322bis]
	Resnick, P., "Internet Message Format", March 2021,		Resnick, P., "Internet Message Format", March 2021,
	<https://datatracker.ietf.org/doc/draft-resnick-		<https://datatracker.ietf.org/doc/draft-resnick-
	rfc5322bis/>.		rfc5322bis/>.
	skipping to change at page 6, line 21 ¶		skipping to change at page 8, line 9 ¶
	<https://www.rfc-editor.org/info/rfc2822>.		<https://www.rfc-editor.org/info/rfc2822>.
	[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,		[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
	DOI 10.17487/RFC5321, October 2008,		DOI 10.17487/RFC5321, October 2008,
	<https://www.rfc-editor.org/info/rfc5321>.		<https://www.rfc-editor.org/info/rfc5321>.
	[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,		[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
	DOI 10.17487/RFC5322, October 2008,		DOI 10.17487/RFC5322, October 2008,
	<https://www.rfc-editor.org/info/rfc5322>.		<https://www.rfc-editor.org/info/rfc5322>.
			[RFC6648] Saint-Andre, P., Nottingham, N., Ed., and D. Crocker,
			"Deprecating the "X-" Prefix and Similar Constructs in
			Application Protocols", June 2012,
			<https://www.rfc-editor.org/info/rfc6648>.
	Appendix A. Change Log		Appendix A. Change Log
	RFC Editor: Please remove this appendix before publication.		RFC Editor: Please remove this appendix before publication.
	A.1. Changes from draft-klensin-email-core-as-00 (2020-03-30) to draft-		A.1. Changes from draft-klensin-email-core-as-00 (2020-03-30) to draft-
	ietf-emailcore-as-00		ietf-emailcore-as-00
	o Change of filename, metadata, and date to reflect transition to WG		o Change of filename, metadata, and date to reflect transition to WG
	document for new emailcore WG. No other substantive changes		document for new emailcore WG. No other substantive changes
	skipping to change at page 6, line 43 ¶		skipping to change at page 8, line 36 ¶
	o Added co-authors (list is in alphabetical order for the present).		o Added co-authors (list is in alphabetical order for the present).
	o Updated references to 5321bis and 5322bis.		o Updated references to 5321bis and 5322bis.
	o Added note at top, "This version is provided as a document		o Added note at top, "This version is provided as a document
	management convenience to update the author list and make an un-		management convenience to update the author list and make an un-
	expired version available to the WG. There are no substantive		expired version available to the WG. There are no substantive
	changes from the prior version", which should be removed for		changes from the prior version", which should be removed for
	version -02.		version -02.
			A.3. Changes from draft-ietf-emailcore-as-01 (2021-04-09) to -02
			o Added new editors and also added some issues the emailcore group
			will be dealing with.
			o Added reference to RFC 6648.
	Authors' Addresses		Authors' Addresses
	John C Klensin (editor)		John C Klensin (editor)
	1770 Massachusetts Ave, Ste 322		1770 Massachusetts Ave, Ste 322
	Cambridge, MA 02140		Cambridge, MA 02140
	USA		USA
	Phone: +1 617 245 1457		Phone: +1 617 245 1457
	Email: john-ietf@jck.com		Email: john-ietf@jck.com
	Kenneth Murchison		Kenneth Murchison
End of changes. 21 change blocks.
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