draft-ietf-eai-rfc5336bis-12.txt   draft-ietf-eai-rfc5336bis-13.txt 
Network Working Group J. Yao Network Working Group J. Yao
Internet-Draft W. Mao Internet-Draft W. Mao
Obsoletes: 5336 (if approved) CNNIC Obsoletes: 5336 (if approved) CNNIC
Intended status: Standards Track August 11, 2011 Intended status: Standards Track September 16, 2011
Expires: February 12, 2012 Expires: March 19, 2012
SMTP Extension for Internationalized Email SMTP Extension for Internationalized Email
draft-ietf-eai-rfc5336bis-12.txt draft-ietf-eai-rfc5336bis-13.txt
Abstract Abstract
This document specifies an SMTP extension for transport and delivery This document specifies an SMTP extension for transport and delivery
of email messages with internationalized email addresses or header of email messages with internationalized email addresses or header
information. information.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 February 12, 2012. This Internet-Draft will expire on March 19, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Updates to Other Specifications . . . . . . . . . . . . . 5 1.2. Updates to Other Specifications . . . . . . . . . . . . . 5
2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 5 2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 5
3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 5 3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 5
3.1. Framework for the Internationalization Extension . . . . . 5 3.1. Framework for the Internationalization Extension . . . . . 5
3.2. The UTF8SMTPbis Extension . . . . . . . . . . . . . . . . 6 3.2. The UTF8SMTPbis Extension . . . . . . . . . . . . . . . . 6
3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7 3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7
3.4. MAIL Command Parameter Usage . . . . . . . . . . . . . . . 8 3.4. MAIL Command Parameter Usage . . . . . . . . . . . . . . . 9
3.5. Non-ASCII addresses and Reply-codes . . . . . . . . . . . 9 3.5. Non-ASCII addresses and Reply-codes . . . . . . . . . . . 9
3.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 10 3.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 10
3.7. Additional ESMTP Changes and Clarifications . . . . . . . 10 3.7. Additional ESMTP Changes and Clarifications . . . . . . . 10
3.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 10 3.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 11
3.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 11 3.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 11
3.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11 3.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11
3.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 11 3.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 16 7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. draft-yao-eai-rfc5336bis: Version 00 . . . . . . . . . . . 16 7.1. draft-yao-eai-rfc5336bis: Version 00 . . . . . . . . . . . 17
7.2. draft-ietf-eai-rfc5336bis: Version 00 . . . . . . . . . . 17 7.2. draft-ietf-eai-rfc5336bis: Version 00 . . . . . . . . . . 17
7.3. draft-ietf-eai-rfc5336bis: Version 01 . . . . . . . . . . 17 7.3. draft-ietf-eai-rfc5336bis: Version 01 . . . . . . . . . . 17
7.4. draft-ietf-eai-rfc5336bis: Version 02 . . . . . . . . . . 17 7.4. draft-ietf-eai-rfc5336bis: Version 02 . . . . . . . . . . 17
7.5. draft-ietf-eai-rfc5336bis: Version 03 . . . . . . . . . . 17 7.5. draft-ietf-eai-rfc5336bis: Version 03 . . . . . . . . . . 17
7.6. draft-ietf-eai-rfc5336bis: Version 04 . . . . . . . . . . 17 7.6. draft-ietf-eai-rfc5336bis: Version 04 . . . . . . . . . . 17
7.7. draft-ietf-eai-rfc5336bis: Version 05 . . . . . . . . . . 17 7.7. draft-ietf-eai-rfc5336bis: Version 05 . . . . . . . . . . 17
7.8. draft-ietf-eai-rfc5336bis: Version 06 . . . . . . . . . . 17 7.8. draft-ietf-eai-rfc5336bis: Version 06 . . . . . . . . . . 17
7.9. draft-ietf-eai-rfc5336bis: Version 07 . . . . . . . . . . 17 7.9. draft-ietf-eai-rfc5336bis: Version 07 . . . . . . . . . . 17
7.10. draft-ietf-eai-rfc5336bis: Version 08 . . . . . . . . . . 17 7.10. draft-ietf-eai-rfc5336bis: Version 08 . . . . . . . . . . 17
7.11. draft-ietf-eai-rfc5336bis: Version 09 . . . . . . . . . . 18 7.11. draft-ietf-eai-rfc5336bis: Version 09 . . . . . . . . . . 18
7.12. draft-ietf-eai-rfc5336bis: Version 10 . . . . . . . . . . 18 7.12. draft-ietf-eai-rfc5336bis: Version 10 . . . . . . . . . . 18
7.13. draft-ietf-eai-rfc5336bis: Version 11 . . . . . . . . . . 18 7.13. draft-ietf-eai-rfc5336bis: Version 11 . . . . . . . . . . 18
7.14. draft-ietf-eai-rfc5336bis: Version 12 . . . . . . . . . . 18 7.14. draft-ietf-eai-rfc5336bis: Version 12 . . . . . . . . . . 18
7.15. draft-ietf-eai-rfc5336bis: Version 13 . . . . . . . . . . 18
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18
8.2. Informative References . . . . . . . . . . . . . . . . . . 20 8.2. Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
The document defines a Simple Mail Transfer Protocol [RFC5321] The document defines a Simple Mail Transfer Protocol [RFC5321]
extension so servers can advertise the ability to accept and process extension so servers can advertise the ability to accept and process
internationalized email addresses (see section 1.1), and internationalized email addresses (see section 1.1), and
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An SMTP server that announces this UTF8SMTPbis extension MUST be An SMTP server that announces this UTF8SMTPbis extension MUST be
prepared to accept a UTF-8 string [RFC3629] in any position in which prepared to accept a UTF-8 string [RFC3629] in any position in which
RFC 5321 specifies that a <mailbox> can appear. Although the RFC 5321 specifies that a <mailbox> can appear. Although the
characters in the <local-part> are permitted to contain non-ASCII characters in the <local-part> are permitted to contain non-ASCII
characters, actual parsing of the <local-part>, and the delimiters characters, actual parsing of the <local-part>, and the delimiters
used, are unchanged from the base email specification [RFC5321]. Any used, are unchanged from the base email specification [RFC5321]. Any
domain name to be looked up in the DNS MUST allow for [RFC5890] domain name to be looked up in the DNS MUST allow for [RFC5890]
behavior. When doing lookups, the UTF8SMTPbis-aware SMTP client or behavior. When doing lookups, the UTF8SMTPbis-aware SMTP client or
server MUST either use a Unicode aware DNS library, or transform the server MUST either use a Unicode aware DNS library, or transform the
internationalized domain name to A-label as described in [RFC5890]. internationalized domain name to the form of A-label as described in
[RFC5890].
An SMTP client that receives the UTF8SMTPbis extension keyword in An SMTP client that receives the UTF8SMTPbis extension keyword in
response to the EHLO command MAY transmit mailbox names within SMTP response to the EHLO command MAY transmit mailbox names within SMTP
commands as internationalized strings in UTF-8 form. It MAY send a commands as internationalized strings in UTF-8 form. It MAY send a
UTF-8 header [RFC5335bis] (which may also include mailbox names in UTF-8 header [RFC5335bis] (which may also include mailbox names in
UTF-8). It MAY transmit the domain parts of mailbox names within UTF-8). It MAY transmit the domain parts of mailbox names within
SMTP commands or the message header as A-labels or U-labels SMTP commands or the message header as A-labels or U-labels
[RFC5890]. The presence of the UTF8SMTPbis extension does not change [RFC5890]. The presence of the UTF8SMTPbis extension does not change
RFC 5321 server relaying behaviors. RFC 5321 server relaying behaviors.
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RFC 5234, RFC 5890 or RFC 5335bis, or are extended in this RFC 5234, RFC 5890 or RFC 5335bis, or are extended in this
document. document.
o Extend the definition of <sub-domain> to permit both the RFC 5321 o Extend the definition of <sub-domain> to permit both the RFC 5321
definition and a UTF-8 string in a DNS label that is conforming definition and a UTF-8 string in a DNS label that is conforming
with IDNA definitions [RFC5890]. with IDNA definitions [RFC5890].
o Extend the definition of <atext> to permit both the RFC 5321 o Extend the definition of <atext> to permit both the RFC 5321
definition and a UTF-8 string. That string MUST NOT contain any definition and a UTF-8 string. That string MUST NOT contain any
of the ASCII graphics or controls characters. of the ASCII graphics or controls characters.
The following ABNF rules will be imported from RFC 5321, section The following ABNF rules imported from RFC 5321, section 4.1.2 are
4.1.2 directly: updated directly or indirectly by this document:
o <Mailbox> o <Mailbox>
o <Local-part> o <Local-part>
o <Dot-string> o <Dot-string>
o <Quoted-string> o <Quoted-string>
o <QcontentSMTP> o <QcontentSMTP>
o <Domain> o <Domain>
o <Atom> o <Atom>
The following ABNF rule will be imported from RFC 5335bis, section The following ABNF rule will be imported from RFC 5335bis, section
4.1 directly: 4.1 directly:
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sub-domain =/ U-label sub-domain =/ U-label
; extend the definition of sub-domain in RFC5321, section 4.1.2 ; extend the definition of sub-domain in RFC5321, section 4.1.2
atext =/ UTF8-non-ascii atext =/ UTF8-non-ascii
; extend the definition of atext in RFC5321, section 4.1.2 ; extend the definition of atext in RFC5321, section 4.1.2
qtextSMTP =/ UTF8-non-ascii qtextSMTP =/ UTF8-non-ascii
; extend the definition of qtextSMTP in RFC5321, section 4.1.2 ; extend the definition of qtextSMTP in RFC5321, section 4.1.2
esmtp-value =/ UTF8-non-ascii
; extend the definition of esmtp-value in RFC5321, section 4.1.2
3.4. MAIL Command Parameter Usage 3.4. MAIL Command Parameter Usage
If the envelope or message being sent requires the capabilities of If the envelope or message being sent requires the capabilities of
the UTF8SMTPbis extension, the UTF8SMTPbis-aware SMTP client MUST the UTF8SMTPbis extension, the UTF8SMTPbis-aware SMTP client MUST
supply the UTF8SMTPbis parameter with the MAIL command. If this supply the UTF8SMTPbis parameter with the MAIL command. If this
parameter is provided, it MUST have no value. If the UTF8SMTPbis- parameter is provided, it MUST have no value. If the UTF8SMTPbis-
aware SMTP client is aware that neither the envelope nor the message aware SMTP client is aware that neither the envelope nor the message
being sent requires any of the UTF8SMTPbis extension capabilities, it being sent requires any of the UTF8SMTPbis extension capabilities, it
SHOULD NOT supply the UTF8SMTPbis parameter with the MAIL command. SHOULD NOT supply the UTF8SMTPbis parameter with the MAIL command.
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surprising rejections can happen during temporary or permanent surprising rejections can happen during temporary or permanent
failures, which users might perceive as serious reliability issues. failures, which users might perceive as serious reliability issues.
3.7.3. Trace Information 3.7.3. Trace Information
The trace information <Return-path-line>, <Time-stamp-line> and their The trace information <Return-path-line>, <Time-stamp-line> and their
related rules are defined in in section 4.4 of RFC 5321 [RFC5321]. related rules are defined in in section 4.4 of RFC 5321 [RFC5321].
This document updates <Mailbox> and <Domain> to support non-ASCII This document updates <Mailbox> and <Domain> to support non-ASCII
characters. When the UTF8SMTPbis extension is used, the 'Reverse- characters. When the UTF8SMTPbis extension is used, the 'Reverse-
path' clause of the Return-path-line may include an internationalized path' clause of the Return-path-line may include an internationalized
domain name that uses the U-label form; The 'Stamp' clause ot the domain name that uses the U-label form; The 'Stamp' clause of the
Time-stamp-line may include an internationalized domain name that Time-stamp-line may include an internationalized domain name that
uses the U-label form. uses the U-label form.
If the messages that include trace fields are sent by an UTF8SMTPbis- If the messages that include trace fields are sent by an UTF8SMTPbis-
aware SMTP client or relay server without the UTF8SMTPbis parameter aware SMTP client or relay server without the UTF8SMTPbis parameter
at MAIL commands, trace field values must conform to RFC 5321 at MAIL commands, trace field values must conform to RFC 5321
regardless of the SMTP server's capability. regardless of the SMTP server's capability.
When a UTF8SMTPbis-aware SMTP server adds a trace field to a message When a UTF8SMTPbis-aware SMTP server adds a trace field to a message
that was or will be transmitted with the UTF8SMTPbis parameter at that was or will be transmitted with the UTF8SMTPbis parameter at
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allowed in the reply, and the UTF8SMTPbis-aware SMTP server supports allowed in the reply, and the UTF8SMTPbis-aware SMTP server supports
enhanced mail system status codes [RFC3463], the enhanced reply-code enhanced mail system status codes [RFC3463], the enhanced reply-code
is "X.6.8" [RFC5248] (see section 4), meaning "A reply containing a is "X.6.8" [RFC5248] (see section 4), meaning "A reply containing a
UTF-8 string is REQUIRED to show the mailbox name, but that form of UTF-8 string is REQUIRED to show the mailbox name, but that form of
response is not permitted by the SMTP client". response is not permitted by the SMTP client".
If the SMTP client does not support the UTF8SMTPbis extension, but If the SMTP client does not support the UTF8SMTPbis extension, but
receives a UTF-8 string in a reply, it may not be able to properly receives a UTF-8 string in a reply, it may not be able to properly
report the reply to the user, and some clients might mishandle that report the reply to the user, and some clients might mishandle that
reply. Internationalized messages in replies are only allowed in the reply. Internationalized messages in replies are only allowed in the
commands under the situations described above. Under any other commands under the situations described above.
circumstances, UTF-8 string MUST NOT appear in the reply.
Although UTF-8 form is needed to represent email addresses in Although UTF-8 form is needed to represent email addresses in
responses under the rules specified in this section, this extension responses under the rules specified in this section, this extension
does not permit the use of UTF-8 string for any other purposes. does not permit the use of UTF-8 string for any other purposes.
UTF8SMTPbis-aware SMTP servers MUST NOT include non-ASCII characters UTF8SMTPbis-aware SMTP servers MUST NOT include non-ASCII characters
in replies except in the limited cases specifically permitted in this in replies except in the limited cases specifically permitted in this
section. section.
4. IANA Considerations 4. IANA Considerations
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to the Standard Track document. Significant comments and suggestions to the Standard Track document. Significant comments and suggestions
were received from Xiaodong LEE, Nai-Wen Hsu, Yangwoo KO, Yoshiro were received from Xiaodong LEE, Nai-Wen Hsu, Yangwoo KO, Yoshiro
YONEYA, and other members of the JET team and were incorporated into YONEYA, and other members of the JET team and were incorporated into
the specification. Additional important comments and suggestions, the specification. Additional important comments and suggestions,
and often specific text, were contributed by many members of the WG and often specific text, were contributed by many members of the WG
and design team. Those contributions include material from John C and design team. Those contributions include material from John C
Klensin, Charles Lindsey, Dave Crocker, Harald Tveit Alvestrand, Klensin, Charles Lindsey, Dave Crocker, Harald Tveit Alvestrand,
Marcos Sanz, Chris Newman, Martin Duerst, Edmon Chung, Tony Finch, Marcos Sanz, Chris Newman, Martin Duerst, Edmon Chung, Tony Finch,
Kari Hurtta, Randall Gellens, Frank Ellermann, Alexey Melnikov, Pete Kari Hurtta, Randall Gellens, Frank Ellermann, Alexey Melnikov, Pete
Resnick, S. Moonesamy, Soobok Lee, Shawn Steele, Alfred Hoenes, Resnick, S. Moonesamy, Soobok Lee, Shawn Steele, Alfred Hoenes,
Miguel Garcia, Magnus Westerlund, and Lars Eggert. Of course, none Miguel Garcia, Magnus Westerlund, Joseph Yee and Lars Eggert. Of
of the individuals are necessarily responsible for the combination of course, none of the individuals are necessarily responsible for the
ideas represented here. combination of ideas represented here.
Thanks a lot to Dave Crocker for his comments and helping of ABNF Thanks a lot to Dave Crocker for his comments and helping of ABNF
refinement. refinement.
7. Change History 7. Change History
[[anchor12: RFC Editor: Please remove this section.]] [[anchor12: RFC Editor: Please remove this section.]]
7.1. draft-yao-eai-rfc5336bis: Version 00 7.1. draft-yao-eai-rfc5336bis: Version 00
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conclusion conclusion
improve the texts improve the texts
7.14. draft-ietf-eai-rfc5336bis: Version 12 7.14. draft-ietf-eai-rfc5336bis: Version 12
Update according to Chris Newman's comments Update according to Chris Newman's comments
improve the texts improve the texts
7.15. draft-ietf-eai-rfc5336bis: Version 13
Update the esmpt-value syntax according to Chris Newman's comments
improve the texts
8. References 8. References
8.1. Normative References 8.1. Normative References
[ASCII] American National Standards Institute (formerly United [ASCII] American National Standards Institute (formerly United
States of America Standards Institute), "USA Code for States of America Standards Institute), "USA Code for
Information Interchange", ANSI X3.4-1968, 1968. Information Interchange", ANSI X3.4-1968, 1968.
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033, [RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033,
October 1996. October 1996.
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