draft-ietf-eai-smtpext-13.txt   rfc5336.txt 
Network Working Group J. Yao, Ed. Network Working Group J. Yao, Ed.
Internet-Draft W. Mao, Ed. Request for Comments: 5336 W. Mao, Ed.
Updates: RFC4952, 2821 and 2822 CNNIC Updates: 2821, 2822, 4952 CNNIC
(if approved) July 8, 2008 Category: Experimental September 2008
Intended status: Experimental
Expires: January 9, 2009
SMTP extension for internationalized email address
draft-ietf-eai-smtpext-13.txt
Status of this Memo
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This Internet-Draft will expire on January 9, 2009. This memo defines an Experimental Protocol for the Internet
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Distribution of this memo is unlimited.
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. Communication with systems that do not implement this information. Communication with systems that do not implement this
specification is specified in another document. This document specification is specified in another document. This document
updates some syntaxes and rules defined in RFC 2821 and RFC 2822, and updates some syntaxes and rules defined in RFC 2821 and RFC 2822, and
has some material updating RFC 4952. has some material updating RFC 4952.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Role of this specification . . . . . . . . . . . . . . . . 3 1.1. Role of This Specification . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 4 2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 4
3. Mail Transport-level Protocol . . . . . . . . . . . . . . . . 4 3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 4
3.1. Framework for the Internationalization Extension . . . . . 4 3.1. Framework for the Internationalization Extension . . . . . 4
3.2. The UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5 3.2. The UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5
3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7 3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7
3.4. The ALT-ADDRESS Parameter . . . . . . . . . . . . . . . . 8 3.4. The ALT-ADDRESS Parameter . . . . . . . . . . . . . . . . 9
3.5. ALT-ADDRESS Parameter Usage and Response Codes . . . . . . 10 3.5. ALT-ADDRESS Parameter Usage and Response Codes . . . . . . 10
3.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 10 3.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 11
3.7. Additional ESMTP Changes and Clarifications . . . . . . . 11 3.7. Additional ESMTP Changes and Clarifications . . . . . . . 11
3.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 11 3.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 12
3.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 12 3.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 12
3.7.3. Trace Information . . . . . . . . . . . . . . . . . . 12 3.7.3. Trace Information . . . . . . . . . . . . . . . . . . 12
3.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 13 3.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 13
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17 5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 17 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 17 7.1. Normative References . . . . . . . . . . . . . . . . . . . 18
7.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 17 7.2. Informative References . . . . . . . . . . . . . . . . . . 19
7.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 18 Appendix A. Material Updating RFC 4952 . . . . . . . . . . . . . 20
7.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 18 A.1. Conventional Message and Internationalized Message . . . . 20
7.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 18 A.2. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.6. draft-ietf-eai-smtpext: Version 05 . . . . . . . . . . . . 18 A.3. SMTP Service Extension for DSNs . . . . . . . . . . . . . 20
7.7. draft-ietf-eai-smtpext: Version 06 . . . . . . . . . . . . 18 A.4. Implementation Advice . . . . . . . . . . . . . . . . . . 20
7.8. draft-ietf-eai-smtpext: Version 07 . . . . . . . . . . . . 18 A.5. Applicability of SMTP Extension to Additional Uses . . . . 21
7.9. draft-ietf-eai-smtpext: Version 08 . . . . . . . . . . . . 19
7.10. draft-ietf-eai-smtpext: Version 09 . . . . . . . . . . . . 19
7.11. draft-ietf-eai-smtpext: Version 10 . . . . . . . . . . . . 19
7.12. draft-ietf-eai-smtpext: Version 11 . . . . . . . . . . . . 19
7.13. draft-ietf-eai-smtpext: Version 12 . . . . . . . . . . . . 19
7.14. draft-ietf-eai-smtpext: Version 13 . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . . 21
Appendix A. Material Updating RFC 4952 . . . . . . . . . . . . . 21
A.1. Conventional Message and Internationalized Message . . . . 22
A.2. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
A.3. SMTP Service Extension for DSNs . . . . . . . . . . . . . 22
A.4. Implementation Advice . . . . . . . . . . . . . . . . . . 22
A.5. Applicability of SMTP Extension to Additional Uses . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . . . 24
1. Introduction 1. Introduction
An internationalized email address includes two parts, the local part An internationalized email address includes two parts, the local part
and the domain part. The ways email addresses are used by protocols and the domain part. The ways email addresses are used by protocols
are different from the ways domain names are used. The most critical are different from the ways domain names are used. The most critical
difference is that emails are delivered through a chain of clients difference is that emails are delivered through a chain of clients
and servers while domain names are resolved by name servers looking and servers, while domain names are resolved by name servers looking
up those names in their own tables. In addition to this, the simple up those names in their own tables. In addition to this, the Simple
mail transfer protocol [RFC2821] provides a negotiation mechanism Mail Transfer Protocol [RFC2821] provides a negotiation mechanism
about service extension with which clients can discover server about service extension with which clients can discover server
capabilities and make decisions for further processing. An extended capabilities and make decisions for further processing. An extended
overview of the extension model for internationalized addresses and overview of the extension model for internationalized addresses and
headers appears in [RFC4952], referred to as "the framework document" headers appears in [RFC4952], referred to as "the framework document"
or just as "Framework" elsewhere in this specification. This or just as "Framework" elsewhere in this specification. This
document specifies an SMTP extension to permit internationalized document specifies an SMTP extension to permit internationalized
email addresses in envelopes, and UNICODE characters (encoded in email addresses in envelopes, and UNICODE characters (encoded in
UTF-8) [RFC3629] in headers. UTF-8) [RFC3629] in headers.
1.1. Role of this specification 1.1. Role of This Specification
The framework document specifies the requirements for, and describes The framework document specifies the requirements for, and describes
components of, full internationalization of electronic mail. A components of, full internationalization of electronic mail. A
thorough understanding of the information in that document and in the thorough understanding of the information in that document and in the
base Internet email specifications [RFC2821] [RFC2822] is necessary base Internet email specifications [RFC2821] [RFC2822] is necessary
to understand and implement this specification. to understand and implement this specification.
This document specifies an element of the email internationalization This document specifies an element of the email internationalization
work, specifically the definition of an SMTP extension [RFC2821] for work, specifically the definition of an SMTP extension [RFC2821] for
internationalized email address transport delivery. internationalized email address transport delivery.
skipping to change at page 3, line 49 skipping to change at page 3, line 49
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
The terms "conventional message" and "internationalized message" are The terms "conventional message" and "internationalized message" are
defined in an appendix to this specification. The terms "UTF-8 defined in an appendix to this specification. The terms "UTF-8
string" or "UTF-8 character" are used informally to refer to Unicode string" or "UTF-8 character" are used informally to refer to Unicode
characters encoded in UTF-8 [RFC3629]. All other specialized terms characters encoded in UTF-8 [RFC3629]. All other specialized terms
used in this specification are defined in the framework document or used in this specification are defined in the framework document or
in the base Internet email specifications [RFC2821] [RFC2822]. In in the base Internet email specifications [RFC2821] [RFC2822]. In
particular, the terms "ASCII address", "internationalized email particular, the terms "ASCII address", "internationalized email
address", "non-ASCII address", "i18mail address", "UTF8SMTP", address", "non-ASCII address", "i18mail address", "UTF8SMTP",
"message" and "mailing list" are used in this document according to "message", and "mailing list" are used in this document according to
the definitions in the framework one. the definitions in the framework document.
This specification defines only those Augmented BNF for Syntax
Specifications (ABNF) [RFC5234] syntax rules that are different from
those of the base email specifications [RFC2821][RFC2822] and, where
the earlier rules are upgraded or extended, gives them new names.
When the new rule is a small modification to the older one, it is
typically given a name starting with "u". Rules that are undefined
here may be found in the base email specifications under the same
names.
[[anchor3: NOTE TO RFC EDITOR: Please remove the following text This specification defines only those Augmented BNF (ABNF) [RFC5234]
before publication.]] syntax rules that are different from those of the base email
This specification is being discussed on the EAI mailing list. See specifications [RFC2821][RFC2822] and, where the earlier rules are
https://www1.ietf.org/mailman/listinfo/ima for information about upgraded or extended, gives them new names. When the new rule is a
subscribing. The list's archive is at small modification to the older one, it is typically given a name
http://www1.ietf.org/mail-archive/web/ima/index.html. starting with "u". Rules that are undefined here may be found in the
base email specifications under the same names.
2. Overview of Operation 2. Overview of Operation
This specification describes an optional extension to the email This specification describes an optional extension to the email
transport mechanism that permits non-ASCII [ASCII] characters in both transport mechanism that permits non-ASCII [ASCII] characters in both
the envelope and header fields of messages, which are encoded with the envelope and header fields of messages, which are encoded with
UTF-8 [RFC3629] characters. The extension is identified with the UTF-8 [RFC3629] characters. The extension is identified with the
token "UTF8SMTP". In order to provide information that may be needed token "UTF8SMTP". In order to provide information that may be needed
in downgrading, an optional alternate ASCII address may be needed if in downgrading, an optional alternate ASCII address may be needed if
an SMTP client attempts to transfer an internationalized message and an SMTP client attempts to transfer an internationalized message and
encounters a server that does not support this extension. encounters a server that does not support this extension.
The EAI-utf8header specification [EAI-utf8header] provides the The EAI UTF-8 header specification [RFC5335] provides the details of
details of how and where non-ASCII characters are permitted in the how and where non-ASCII characters are permitted in the header fields
header fields of messages. The context for this specification is of messages. The context for this specification is described in the
described in the framework document. framework document.
3. Mail Transport-level Protocol 3. Mail Transport-Level Protocol
3.1. Framework for the Internationalization Extension 3.1. Framework for the Internationalization Extension
The following service extension is defined: The following service extension is defined:
1. The name of the SMTP service extension is "Email Address 1. The name of the SMTP service extension is "Email Address
Internationalization". Internationalization".
2. The EHLO keyword value associated with this extension is 2. The EHLO keyword value associated with this extension is
"UTF8SMTP". "UTF8SMTP".
3. No parameter values are defined for this EHLO keyword value. In 3. No parameter values are defined for this EHLO keyword value. In
order to permit future (although unanticipated) extensions, the order to permit future (although unanticipated) extensions, the
EHLO response MUST NOT contain any parameters for that keyword. EHLO response MUST NOT contain any parameters for that keyword.
Clients MUST ignore any parameters, that is, clients MUST behave Clients MUST ignore any parameters; that is, clients MUST behave
as if the parameters do not appear. If a server includes as if the parameters do not appear. If a server includes
UTF8SMTP in its EHLO response, it MUST be fully compliant with UTF8SMTP in its EHLO response, it MUST be fully compliant with
this version of this specification. this version of this specification.
4. One optional parameter, ALT-ADDRESS, is added to the MAIL and 4. One optional parameter, ALT-ADDRESS, is added to the MAIL and
RCPT commands of SMTP. ALT-ADDRESS specifies an all-ASCII RCPT commands of SMTP. ALT-ADDRESS specifies an all-ASCII
address which can be used as a substitute for the corresponding address which can be used as a substitute for the corresponding
primary (i18mail) address when downgrading. More discussion of primary (i18mail) address when downgrading. More discussion of
the use of this parameter appears in [RFC4952] and the use of this parameter appears in [RFC4952] and [Downgrade].
[EAI-downgrading].
5. One optional parameter "UTF8REPLY" is added to the VRFY and EXPN 5. One optional parameter "UTF8REPLY" is added to the VRFY and EXPN
commands. The parameter UTF8REPLY has no value. The parameter commands. The parameter UTF8REPLY has no value. The parameter
indicates that the SMTP client can accept Unicode characters in indicates that the SMTP client can accept Unicode characters in
UTF-8 encoding in replies from the VRFY and EXPN commands. UTF-8 encoding in replies from the VRFY and EXPN commands.
6. No additional SMTP verbs are defined by this extension. 6. No additional SMTP verbs are defined by this extension.
7. Servers offering this extension MUST provide support for, and 7. Servers offering this extension MUST provide support for, and
announce, the 8BITMIME extension [RFC1652]. announce, the 8BITMIME extension [RFC1652].
8. The reverse-path and forward-path of the SMTP MAIL and RCPT 8. The reverse-path and forward-path of the SMTP MAIL and RCPT
commands are extended to allow Unicode characters encoded in commands are extended to allow Unicode characters encoded in
UTF-8 in mailbox names (addresses). UTF-8 in mailbox names (addresses).
9. The mail message body is extended as specified in
[EAI-utf8header]. 9. The mail message body is extended as specified in [RFC5335].
10. The maximum length of MAIL and RCPT command lines is increased 10. The maximum length of MAIL and RCPT command lines is increased
by 460 characters by the possible addition of the ALT-ADDRESS by 460 characters by the possible addition of the ALT-ADDRESS
keyword and value. keyword and value.
11. The UTF8SMTP extension is valid on the submission port 11. The UTF8SMTP extension is valid on the submission port
[RFC4409]. [RFC4409].
3.2. The UTF8SMTP Extension 3.2. The UTF8SMTP Extension
An SMTP Server that announces this extension MUST be prepared to An SMTP server that announces this extension MUST be prepared to
accept a UTF-8 string [RFC3629] in any position in which RFC 2821 accept a UTF-8 string [RFC3629] in any position in which RFC 2821
specifies that a mailbox can appear. That string MUST be parsed only specifies that a mailbox can appear. That string MUST be parsed only
as specified in RFC 2821, i.e., by separating the mailbox into source as specified in RFC 2821, i.e., by separating the mailbox into source
route, local part and domain part, using only the characters colon route, local part, and domain part, using only the characters colon
(U+003A), comma (U+002C), and at-sign (U+0040) as specified there. (U+003A), comma (U+002C), and at-sign (U+0040) as specified there.
Once isolated by this parsing process, the local part MUST be treated Once isolated by this parsing process, the local part MUST be treated
as opaque unless the SMTP Server is the final delivery MTA. Any as opaque unless the SMTP server is the final delivery Mail Transfer
domain names that are to be looked up in the DNS MUST first be Agent (MTA). Any domain names that are to be looked up in the DNS
processed into the form specified in IDNA [RFC3490] by means of the MUST first be processed into the form specified in
ToASCII() operation unless they are already in that form. Any domain "Internationalizing Domain Names in Applications (IDNA)" [RFC3490] by
names that are to be compared to local strings SHOULD be checked for means of the ToASCII() operation unless they are already in that
validity and then MUST be compared as specified in section 3.4 of form. Any domain names that are to be compared to local strings
IDNA. SHOULD be checked for validity and then MUST be compared as specified
in Section 3.4 of IDNA.
An SMTP Client that receives the UTF8SMTP extension keyword in An SMTP client that receives the UTF8SMTP 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 [EAI-utf8header] (which may also include mailbox names UTF-8 header [RFC5335] (which may also include mailbox names in
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 in either the form of ACE (ASCII SMTP commands or the message header as either ACE (ASCII Compatible
Compatible Encoding) labels as specified in IDNA [RFC3490] or as Encoding) labels (as specified in IDNA [RFC3490]) or UTF-8 strings.
UTF-8 strings. All labels in domain parts of mailbox names which are All labels in domain parts of mailbox names which are IDNs (either
IDNs (either UTF-8 or ACE strings) MUST be valid. If the original UTF-8 or ACE strings) MUST be valid. If the original client submits
client submits a message to a Message Submission Server ("MSA") a message to a Message Submission Server ("MSA") [RFC4409], it is the
[RFC4409], it is the responsibility of the MSA that all domain labels responsibility of the MSA that all domain labels are valid;
are valid; otherwise it is the original client's responsibility. The otherwise, it is the original client's responsibility. The presence
presence of the UTF8SMTP extension does not change the requirement of of the UTF8SMTP extension does not change the requirement of RFC 2821
RFC 2821 that servers relaying mail MUST NOT attempt to parse, that servers relaying mail MUST NOT attempt to parse, evaluate, or
evaluate, or transform the local part in any way. transform the local part in any way.
If the UTF8SMTP SMTP extension is not offered by the Server, the SMTP If the UTF8SMTP SMTP extension is not offered by the Server, the SMTP
client MUST NOT transmit an internationalized address (For this client MUST NOT transmit an internationalized address and MUST NOT
paragraph, the internationalized domain name in the form of ACE transmit a mail message containing internationalized mail headers as
described in [RFC5335] at any level within its MIME structure. (For
this paragraph, the internationalized domain name in the form of ACE
labels as specified in IDNA [RFC3490] is not considered as labels as specified in IDNA [RFC3490] is not considered as
"internationalized".) and MUST NOT transmit a mail message containing "internationalized".) Instead, if an SMTP client (SMTP sender)
internationalized mail headers as described in [EAI-utf8header] at attempts to transfer an internationalized message and encounters a
any level within its MIME structure. Instead, if an SMTP client server that does not support the extension, it MUST make one of the
(SMTP sender) attempts to transfer an internationalized message and following four choices:
encounters a server that does not support the extension, it MUST make
one of the following four choices:
1. If and only if the SMTP client (sender) is a Message Submission 1. If and only if the SMTP client (sender) is a Message Submission
Server ("MSA") [RFC4409], it MAY, consistent with the general Server ("MSA") [RFC4409], it MAY, consistent with the general
provisions for changes by such servers, rewrite the envelope, provisions for changes by such servers, rewrite the envelope,
headers, or message material to make them entirely ASCII and headers, or message material to make them entirely ASCII and
consistent with the provisions of RFC 2821 [RFC2821] and RFC 2822 consistent with the provisions of RFC 2821 [RFC2821] and RFC 2822
[RFC2822]. [RFC2822].
2. Either reject the message during the SMTP transaction or accept
the message and then generate and transmit a notification of non- 2. It may either reject the message during the SMTP transaction or
deliverability. Such notification MUST be done as specified in accept the message and then generate and transmit a notification
RFC 2821 [RFC2821], RFC 3464 [RFC3464], and the EAI DSN of non-deliverability. Such notification MUST be done as
specification [EAI-dsn]. specified in RFC 2821 [RFC2821], RFC 3464 [RFC3464], and the EAI
3. Find an alternate route to the destination that permits UTF8SMTP. delivery status notification (DSN) specification [RFC5337].
That route may be discovered by trying alternate MX hosts (using
preference rules as specified in RFC 2821) or using other means 3. It may find an alternate route to the destination that permits
available to the SMTP-sender. UTF8SMTP. That route may be discovered by trying alternate Mail
eXchanger (MX) hosts (using preference rules as specified in RFC
2821) or using other means available to the SMTP-sender.
4. If and only if ASCII addresses are available for all addresses 4. If and only if ASCII addresses are available for all addresses
that appear in the return path and the specific forward paths that appear in the return path and the specific forward paths
being attempted, downgrade the message to an all-ASCII form as being attempted, it may downgrade the message to an all-ASCII
specified in [EAI-downgrading]. An ASCII address is considered form as specified in [Downgrade]. An ASCII address is considered
to be "available" for a particular address if the original to be "available" for a particular address if the original
address in the envelope is in ASCII or if an ALT-ADDRESS address in the envelope is in ASCII or if an ALT-ADDRESS
parameter is specified for a UTF8SMTP address. parameter is specified for a UTF8SMTP address.
The difference between "choice 1" and "choice 4" is that "choice 1" The difference between choice 1 and choice 4 is that choice 1 is
is constrained by Message Submission [RFC4409], while "choice 4" is constrained by Message Submission [RFC4409], while choice 4 is
constrained by [EAI-downgrading]. constrained by [Downgrade].
3.3. Extended Mailbox Address Syntax 3.3. Extended Mailbox Address Syntax
RFC 2821, section 4.1.2, defines the syntax of a mailbox entirely in RFC 2821, Section 4.1.2, defines the syntax of a mailbox entirely in
terms of ASCII characters, using the production for a mailbox and terms of ASCII characters, using the production for a mailbox and
those on which it depends. those productions on which it depends.
The key changes made by this specification are, informally, to The key changes made by this specification are, informally, to
o Change the definition of "sub-domain" to permit either the o Change the definition of "sub-domain" to permit either the
definition above or a UTF-8 string representing a DNS label that definition above or a UTF-8 string representing a DNS label that
is conformant with IDNA [RFC3490]. is conformant with IDNA [RFC3490].
o Change the definition of "Atom" to permit either the definition o Change the definition of "Atom" to permit either the definition
above or a UTF-8 string. That string MUST NOT contain any of the above or a UTF-8 string. That string MUST NOT contain any of the
ASCII characters (either graphics or controls) that are not ASCII characters (either graphics or controls) that are not
permitted in "atext"; it is otherwise unrestricted. permitted in "atext"; it is otherwise unrestricted.
According to the description above, the syntax of an According to the description above, the syntax of an
internationalized email mailbox name (address) is defined in ABNF internationalized email mailbox name (address) is defined in ABNF
[RFC5234] as [RFC5234] as follows.
uMailbox = uLocal-part "@" uDomain uMailbox = uLocal-part "@" uDomain
; Replace Mailbox in RFC 2821, section 4.1.2 ; Replace Mailbox in RFC 2821, Section 4.1.2
uLocal-part = uDot-string / uQuoted-string uLocal-part = uDot-string / uQuoted-string
; MAY be case-sensitive ; MAY be case-sensitive
; Replace Local-part in RFC 2821, section 4.1.2 ; Replace Local-part in RFC 2821, Section 4.1.2
uDot-string = uAtom *("." uAtom) uDot-string = uAtom *("." uAtom)
; Replace Dot-string in RFC 2821, section 4.1.2 ; Replace Dot-string in RFC 2821, Section 4.1.2
uAtom = 1*ucharacter uAtom = 1*ucharacter
; Replace Atom in RFC 2821, section 4.1.2 ; Replace Atom in RFC 2821, Section 4.1.2
ucharacter = atext / UTF8-non-ascii ucharacter = atext / UTF8-non-ascii
atext = <See section 3.2.4 of RFC 2822> atext = <See Section 3.2.4 of RFC 2822>
uQuoted-string = DQUOTE *uqcontent DQUOTE uQuoted-string = DQUOTE *uqcontent DQUOTE
; Replace Quoted-string in RFC 2821, section 4.1.2 ; Replace Quoted-string in RFC 2821, Section 4.1.2
DQUOTE = <See appendix B.1 of RFC 5234> DQUOTE = <See appendix B.1 of RFC 5234>
uqcontent = qcontent / UTF8-non-ascii uqcontent = qcontent / UTF8-non-ascii
qcontent = <See section 3.2.5 of RFC 2822> qcontent = <See Section 3.2.5 of RFC 2822>
uDomain = (sub-udomain 1*("." sub-udomain)) / address-literal uDomain = (sub-udomain 1*("." sub-udomain)) / address-literal
; Replace Domain in RFC 2821, section 4.1.2 ; Replace Domain in RFC 2821, Section 4.1.2
address-literal = <See section 4.1.2 of RFC 2822> address-literal = <See Section 4.1.2 of RFC 2822>
sub-udomain = uLet-dig [uLdh-str] sub-udomain = uLet-dig [uLdh-str]
; Replace sub-domain in RFC 2821, section 4.1.2 ; Replace sub-domain in RFC 2821, Section 4.1.2
uLet-dig = Let-dig / UTF8-non-ascii uLet-dig = Let-dig / UTF8-non-ascii
Let-dig = <See section 4.1.3 of RFC 2821> Let-dig = <See Section 4.1.3 of RFC 2821>
uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-non-ascii) uLet-dig uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-non-ascii) uLet-dig
; Replace Ldh-str in RFC 2821, section 4.1.3 ; Replace Ldh-str in RFC 2821, Section 4.1.3
UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4 UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4
UTF8-2 = <See section 4 of RFC 3629> UTF8-2 = <See Section 4 of RFC 3629>
UTF8-3 = <See section 4 of RFC 3629>
UTF8-4 = <See section 4 of RFC 3629> UTF8-3 = <See Section 4 of RFC 3629>
UTF8-4 = <See Section 4 of RFC 3629>
The value of "uDomain" SHOULD be verified by applying the tests The value of "uDomain" SHOULD be verified by applying the tests
specified as part of IDNA [RFC3490]. If that verification fails, the specified as part of IDNA [RFC3490]. If that verification fails, the
email address with that uDomain MUST NOT be regarded as a valid email email address with that uDomain MUST NOT be regarded as a valid email
address. address.
3.4. The ALT-ADDRESS Parameter 3.4. The ALT-ADDRESS Parameter
If the UTF8SMTP extension is offered, the syntax of the SMTP MAIL and If the UTF8SMTP extension is offered, the syntax of the SMTP MAIL and
RCPT commands is extended to support the optional esmtp-keyword "ALT- RCPT commands is extended to support the optional esmtp-keyword "ALT-
ADDRESS". That keyword specifies an alternate all-ASCII address ADDRESS". That keyword specifies an alternate all-ASCII address that
which may be used when downgrading. If the ALT-ADDRESS esmtp-keyword may be used when downgrading. If the ALT-ADDRESS esmtp-keyword is
is used, it MUST have an associated esmtp-value (ALT-ADDRESS-esmtp- used, it MUST have an associated esmtp-value (ALT-ADDRESS-esmtp-
value, which is defined below). value, which is defined below).
While it may be tempting to consider ALT-ADDRESS as a general-purpose While it may be tempting to consider ALT-ADDRESS as a general-purpose
second-chance address, such behavior is not defined here. Instead, second-chance address, such behavior is not defined here. Instead,
in this specification ALT-ADDRESS only has meaning when the in this specification ALT-ADDRESS only has meaning when the
associated primary address is non-ASCII and the message is associated primary address is non-ASCII and the message is
downgraded. This restriction allows for future extension of the downgraded. This restriction allows for future extension of the
specification even though no such extensions are currently specification even though no such extensions are currently
anticipated. anticipated.
Based on the definition of mail-parameters in [RFC2821], the ALT- Based on the definition of mail-parameters in [RFC2821], the ALT-
ADDRESS parameter usage in the commands of "MAIL" and "RCPT" is ADDRESS parameter usage in the commands of MAIL and RCPT is defined
defined as follows. The following definitions are given in the same as follows. The following definitions are given in the same format
format as used in RFC 2821. as used in RFC 2821.
"MAIL FROM:" ("<>" / uReverse-path) [ SP Mail-parameters ] CRLF "MAIL FROM:" ("<>" / uReverse-path) [ SP Mail-parameters ] CRLF
; Update the MAIL command in RFC 2821, section 4.1.1.2. ; Update the MAIL command in RFC 2821, Section 4.1.1.2.
; A new parameter defined by the ABNF non-terminal ; A new parameter defined by the ABNF non-terminal
; <ALT-ADDRESS-parameter> is added. It complies ; <ALT-ADDRESS-parameter> is added. It complies
; with the syntax specified for <esmtp-param> in RFC 2821. ; with the syntax specified for <esmtp-param> in RFC 2821.
"RCPT TO:" ("<Postmaster@" uDomain ">" / "<Postmaster>" / "RCPT TO:" ("<Postmaster@" uDomain ">" / "<Postmaster>" /
uForward-path) [ SP Rcpt-parameters ] CRLF uForward-path) [ SP Rcpt-parameters ] CRLF
; Update RCPT command in RFC 2821, section 4.1.1.3. ; Update RCPT command in RFC 2821, Section 4.1.1.3.
; A new parameter defined by the ABNF non-terminal ; A new parameter defined by the ABNF non-terminal
; <ALT-ADDRESS-parameter> is added. It complies ; <ALT-ADDRESS-parameter> is added. It complies
; with the syntax specified for <esmtp-param>. ; with the syntax specified for <esmtp-param>.
; uDomain is defined in section 3.3 of this document ; uDomain is defined in Section 3.3 of this document.
uReverse-path = uPath uReverse-path = uPath
; Replace Reverse-path in RFC 2821, section 4.1.2 ; Replace Reverse-path in RFC 2821, Section 4.1.2.
uForward-path = uPath uForward-path = uPath
; Replace Forward-path in RFC 2821, section 4.1.2 ; Replace Forward-path in RFC 2821, Section 4.1.2.
uPath = "<" [ A-d-l ":" ] uMailbox ">" uPath = "<" [ A-d-l ":" ] uMailbox ">"
; Replace Path in RFC 2821, section 4.1.2 ; Replace Path in RFC 2821, Section 4.1.2.
; uMailbox is defined in section 3.3 of this document ; uMailbox is defined in Section 3.3 of this document.
A-d-l = <See Section 4.1.2 of RFC 2821>
A-d-l = <See section 4.1.2 of RFC 2821>
ALT-ADDRESS-parameter="ALT-ADDRESS=" ALT-ADDRESS-value ALT-ADDRESS-parameter="ALT-ADDRESS=" ALT-ADDRESS-value
ALT-ADDRESS-value= xtext ALT-ADDRESS-value= xtext
; The value is a mailbox name encoded as xtext. ; The value is a mailbox name encoded as xtext.
xtext= <See section 4.2 of RFC 3461> xtext = <See Section 4.2 of RFC 3461>
The ALT-ADDRESS-parameter MUST NOT appear more than once in any MAIL The ALT-ADDRESS-parameter MUST NOT appear more than once in any MAIL
or RCPT command. ALT-ADDRESS-esmtp-value MUST be an all-ASCII email or RCPT command. ALT-ADDRESS-esmtp-value MUST be an all-ASCII email
address before xtext encoding. address before xtext encoding.
3.5. ALT-ADDRESS Parameter Usage and Response Codes 3.5. ALT-ADDRESS Parameter Usage and Response Codes
An "internationalized message" as defined in the appendix of this An "internationalized message" as defined in the appendix of this
specification MUST NOT be sent to an SMTP server that does not specification MUST NOT be sent to an SMTP server that does not
support UTF8SMTP. Such a message MAY be rejected by a server if it support UTF8SMTP. Such a message MAY be rejected by a server if it
skipping to change at page 10, line 32 skipping to change at page 10, line 39
The three-digit reply codes used in this section are consistent with The three-digit reply codes used in this section are consistent with
their meanings as defined in RFC 2821. their meanings as defined in RFC 2821.
When messages are rejected because the RCPT command requires an ALT- When messages are rejected because the RCPT command requires an ALT-
ADDRESS, the response code 553 is used with the meaning "mailbox name ADDRESS, the response code 553 is used with the meaning "mailbox name
not allowed". When messages are rejected for other reasons, such as not allowed". When messages are rejected for other reasons, such as
the MAIL command requiring an ALT-ADDRESS, the response code 550 is the MAIL command requiring an ALT-ADDRESS, the response code 550 is
used with the meaning "mailbox unavailable". When the server used with the meaning "mailbox unavailable". When the server
supports enhanced mail system status codes [RFC3463], response code supports enhanced mail system status codes [RFC3463], response code
"5.6.x" [SMTP-codes] is used, meaning that "The ALT-ADDRESS is "X.6.7" [RFC5248] is used, meaning that "The ALT-ADDRESS is required
required but not specified". but not specified".
If the response code is issued after the final "." of the DATA If the response code is issued after the final "." of the DATA
command, the response code "554" is used with the meaning command, the response code "554" is used with the meaning
"Transaction failed". When the server supports enhanced mail system "Transaction failed". When the server supports enhanced mail system
status codes [RFC3463], response code "5.6.z" [SMTP-codes] is used, status codes [RFC3463], response code "X.6.9" [RFC5248] is used,
meaning that "UTF8SMTP downgrade failed". meaning that "UTF8SMTP downgrade failed".
[[anchor6: RFC Editor: please insert the proper error codes for
"5.6.x" and "5.6.z" after IANA has made the relevant assignments.]]
3.6. Body Parts and SMTP Extensions 3.6. Body Parts and SMTP Extensions
There is no ESMTP parameter to assert that a message is an There is no ESMTP parameter to assert that a message is an
internationalized message. An SMTP server that requires accurate internationalized message. An SMTP server that requires accurate
knowledge of whether a message is internationalized is required to knowledge of whether a message is internationalized is required to
parse all message header fields and MIME header fields in the message parse all message header fields and MIME header fields in the message
body. body.
While this specification requires that servers support the 8BITMIME While this specification requires that servers support the 8BITMIME
extension [RFC1652] to ensure that servers have adequate handling extension [RFC1652] to ensure that servers have adequate handling
skipping to change at page 11, line 20 skipping to change at page 11, line 27
require non-ASCII body parts in the MIME message. The UTF8SMTP require non-ASCII body parts in the MIME message. The UTF8SMTP
extension MAY be used with the BODY=8BITMIME parameter if that is extension MAY be used with the BODY=8BITMIME parameter if that is
appropriate given the body content or, with the BODY=BINARYMIME appropriate given the body content or, with the BODY=BINARYMIME
parameter, if the server advertises BINARYMIME [RFC3030] and that is parameter, if the server advertises BINARYMIME [RFC3030] and that is
appropriate. appropriate.
Assuming that the server advertises UTF8SMTP and 8BITMIME, and Assuming that the server advertises UTF8SMTP and 8BITMIME, and
receives at least one non-ASCII address, with or without ALT-ADDRESS, receives at least one non-ASCII address, with or without ALT-ADDRESS,
the precise interpretation of 'No BODY parameter', "BODY=8BITMIME", the precise interpretation of 'No BODY parameter', "BODY=8BITMIME",
and "BODY=BINARYMIME" in the MAIL command is: and "BODY=BINARYMIME" in the MAIL command is:
1. If there is no BODY parameter, the header contains UTF-8 1. If there is no BODY parameter, the header contains UTF-8
characters, but all the body parts are in ASCII (possibly as the characters, but all the body parts are in ASCII (possibly as the
result of a Content-transfer-encoding). result of a content-transfer-encoding).
2. If a BODY=8BITMIME parameter is present, the header contains 2. If a BODY=8BITMIME parameter is present, the header contains
UTF-8 characters and some or all of the body parts contain 8-bit UTF-8 characters, and some or all of the body parts contain 8-bit
line-oriented data. line-oriented data.
3. If a BODY=BINARYMIME parameter is present, the header contains 3. If a BODY=BINARYMIME parameter is present, the header contains
UTF-8 characters and some or all body parts contain binary data UTF-8 characters, and some or all body parts contain binary data
without restriction as to line lengths or delimiters. without restriction as to line lengths or delimiters.
3.7. Additional ESMTP Changes and Clarifications 3.7. Additional ESMTP Changes and Clarifications
The information carried in the mail transport process involves The information carried in the mail transport process involves
addresses ("mailboxes") and domain names in various contexts in addresses ("mailboxes") and domain names in various contexts in
addition to the MAIL and RCPT commands and extended alternatives to addition to the MAIL and RCPT commands and extended alternatives to
them. In general, the rule is that, when RFC 2821 specifies a them. In general, the rule is that, when RFC 2821 specifies a
mailbox, this specification expects UTF-8 to be used for the entire mailbox, this specification expects UTF-8 to be used for the entire
string; when RFC 2821 specifies a domain name, the name SHOULD be in string; when RFC 2821 specifies a domain name, the name SHOULD be in
the form of ACE labels if its raw form is non-ASCII. the form of ACE labels if its raw form is non-ASCII.
The following subsections list and discuss all of the relevant cases. The following subsections list and discuss all of the relevant cases.
3.7.1. The Initial SMTP Exchange 3.7.1. The Initial SMTP Exchange
When an SMTP connection is opened, the server normally sends a When an SMTP connection is opened, the server normally sends a
"greeting" response consisting of the '220' reply code and some "greeting" response consisting of the 220 response code and some
information. The client then sends the EHLO command. Since the information. The client then sends the EHLO command. Since the
client cannot know whether the server supports UTF8SMTP until after client cannot know whether the server supports UTF8SMTP until after
it receives the response from EHLO, any domain names that appear in it receives the response from EHLO, any domain names that appear in
this dialogue, or in responses to EHLO, MUST be in the hostname form, this dialogue, or in responses to EHLO, MUST be in the hostname form,
i.e., internationalized ones MUST be in the form of ACE labels. i.e., internationalized ones MUST be in the form of ACE labels.
3.7.2. Mail eXchangers 3.7.2. Mail eXchangers
Organizations often authorize multiple servers to accept mail Organizations often authorize multiple servers to accept mail
addressed to them. For example, the organization may itself operate addressed to them. For example, the organization may itself operate
skipping to change at page 12, line 26 skipping to change at page 12, line 36
reliability issue. reliability issue.
3.7.3. Trace Information 3.7.3. Trace Information
When an SMTP server receives a message for delivery or further When an SMTP server receives a message for delivery or further
processing, it MUST insert trace ("time stamp" or "Received") processing, it MUST insert trace ("time stamp" or "Received")
information at the beginning of the message content. "Time stamp" or information at the beginning of the message content. "Time stamp" or
"Received" appears in the form of "Received:" lines. The most "Received" appears in the form of "Received:" lines. The most
important use of Received: lines is for debugging mail faults. When important use of Received: lines is for debugging mail faults. When
the delivery SMTP server makes the "final delivery" of a message, it the delivery SMTP server makes the "final delivery" of a message, it
inserts a return-path line at the beginning of the mail data. The inserts a Return-path line at the beginning of the mail data. The
primary purpose of the Return-path is to designate the address to primary purpose of the Return-path is to designate the address to
which messages indicating non-delivery or other mail system failures which messages indicating non-delivery or other mail system failures
are to be sent. For the trace information, this memo updates the are to be sent. For the trace information, this memo updates the
time stamp line and the return path line [RFC2821] formally defined time stamp line and the return path line [RFC2821] formally defined
as follows: as follows:
uReturn-path-line = "Return-Path:" FWS uReverse-path <CRLF> uReturn-path-line = "Return-Path:" FWS uReverse-path <CRLF>
; Replaces Return-path-line in section 4.4 of RFC2821 ; Replaces Return-path-line in Section 4.4 of RFC 2821
; uReverse-path is defined in Section 3.3 of this document ; uReverse-path is defined in Section 3.3 of this document
uTime-stamp-line = "Received:" FWS uStamp <CRLF> uTime-stamp-line = "Received:" FWS uStamp <CRLF>
; Replaces Time-stamp-line in section 4.4 of RFC2821 ; Replaces Time-stamp-line in Section 4.4 of RFC 2821
uStamp = From-domain By-domain uOpt-info ";" FWS date-time uStamp = From-domain By-domain uOpt-info ";" FWS date-time
; Replaces Stamp in section 4.4 of RFC2821 ; Replaces Stamp in Section 4.4 of RFC 2821
uOpt-info = [Via] [With] [ID] [uFor] uOpt-info = [Via] [With] [ID] [uFor]
; Replaces Opt-info in section 4.4 of RFC2821 ; Replaces Opt-info in Section 4.4 of RFC 2821
; The protocol value for With will allow a UTF8SMTP value ; The protocol value for With will allow a UTF8SMTP value
uFor = "FOR" ( FWS (uPath / uMailbox) ) CFWS uFor = "FOR" ( FWS (uPath / uMailbox) ) CFWS
; Replaces For in section 4.4 of RFC2821 ; Replaces For in Section 4.4 of RFC 2821
; uPath and uMailbox are defined in Sections 2.4 and ; uPath and uMailbox are defined in Sections 2.4 and
; 2.3, respectively, of this document ; 2.3, respectively, of this document
Note: The FOR parameter has been changed to match the definition in Note: The FOR parameter has been changed to match the definition in
[RFC2821bis], permitting only one address in the For clause. The [RFC2821bis], permitting only one address in the For clause. The
group working on that document reached mailing list consensus that group working on that document reached mailing list consensus that
the syntax in [RFC2821] that permitted more than one address was the syntax in [RFC2821] that permitted more than one address was
simply a mistake. simply a mistake.
Except in the 'uFor' clause and 'uReverse-path' value where non-ASCII Except in the 'uFor' clause and 'uReverse-path' value where non-ASCII
skipping to change at page 13, line 32 skipping to change at page 13, line 36
3.7.4. UTF-8 Strings in Replies 3.7.4. UTF-8 Strings in Replies
3.7.4.1. MAIL and RCPT Commands 3.7.4.1. MAIL and RCPT Commands
If the client issues a RCPT command containing non-ASCII characters, If the client issues a RCPT command containing non-ASCII characters,
the SMTP server is permitted to use UTF-8 characters in the email the SMTP server is permitted to use UTF-8 characters in the email
address associated with 251 and 551 response codes. address associated with 251 and 551 response codes.
If an SMTP client follows this specification and sends any RCPT If an SMTP client follows this specification and sends any RCPT
commands containing non-ASCII addresses, it MUST be able to accept commands containing non-ASCII addresses, it MUST be able to accept
and process 251 or 551 replies containing UTF-8 email addresses. If and process 251 or 551 responses containing UTF-8 email addresses.
a given RCPT command does not include a non-ASCII envelope address, If a given RCPT command does not include a non-ASCII envelope
the server MUST NOT return a 251 or 551 response containing a non- address, the server MUST NOT return a 251 or 551 response containing
ASCII mailbox. Instead, it MUST transform such responses into 250 or a non-ASCII mailbox. Instead, it MUST transform such responses into
550 responses that do not contain addresses. 250 or 550 responses that do not contain addresses.
3.7.4.2. VRFY and EXPN Commands and the UTF8REPLY Parameter 3.7.4.2. VRFY and EXPN Commands and the UTF8REPLY Parameter
If the VRFY and EXPN commands are transmitted with an optional If the VRFY and EXPN commands are transmitted with an optional
parameter "UTF8REPLY", it indicates the client can accept UTF-8 parameter "UTF8REPLY", it indicates the client can accept UTF-8
strings in replies from those commands. This allows the server to strings in replies from those commands. This allows the server to
use UTF-8 strings in mailbox names and full names which occur in use UTF-8 strings in mailbox names and full names that occur in
replies without concern that the client might be confused by them. replies without concern that the client might be confused by them.
An SMTP client that conforms to this specification MUST accept and An SMTP client that conforms to this specification MUST accept and
correctly process replies from the VRFY and EXPN commands that correctly process replies from the VRFY and EXPN commands that
contain UTF-8 strings. However the SMTP server MUST NOT use UTF-8 contain UTF-8 strings. However, the SMTP server MUST NOT use UTF-8
strings in replies if the SMTP client does not specifically allow strings in replies if the SMTP client does not specifically allow
such replies by transmitting this parameter. Most replies do not such replies by transmitting this parameter. Most replies do not
require that a mailbox name be included in the returned text and require that a mailbox name be included in the returned text, and
therefore UTF-8 is not needed in them. Some replies, notably those therefore UTF-8 is not needed in them. Some replies, notably those
resulting from successful execution of the VRFY and EXPN commands, do resulting from successful execution of the VRFY and EXPN commands, do
include the mailbox, making the provisions of this section important. include the mailbox, making the provisions of this section important.
VERIFY (VRFY) and EXPAND (EXPN) command syntaxes are changed to: VERIFY (VRFY) and EXPAND (EXPN) command syntaxes are changed to:
"VRFY" SP (uLocal-part / uMailbox) [SP "UTF8REPLY"] CRLF "VRFY" SP (uLocal-part / uMailbox) [SP "UTF8REPLY"] CRLF
; uLocal-part and uMailbox are defined in ; uLocal-part and uMailbox are defined in
; Section 3.3 of this document ; Section 3.3 of this document.
"EXPN" SP ( uLocal-part / uMailbox ) [ SP "UTF8REPLY" ] CRLF "EXPN" SP ( uLocal-part / uMailbox ) [ SP "UTF8REPLY" ] CRLF
; uLocal-part and uMailbox are defined in ; uLocal-part and uMailbox are defined in
; Section 3.3 of this document ; Section 3.3 of this document.
The "UTF8REPLY" parameter does not use a value. If the reply to a The "UTF8REPLY" parameter does not use a value. If the reply to a
VERIFY (VRFY) or EXPAND (EXPN) command requires UTF-8, but the SMTP VERIFY (VRFY) or EXPAND (EXPN) command requires UTF-8, but the SMTP
client does not use the "UTF8REPLY" parameter, then the server MUST client does not use the "UTF8REPLY" parameter, then the server MUST
use either the reply code 252 or 550. Response code 252, defined in use either the response code 252 or 550. Response code 252, defined
[RFC2821], means "Cannot VRFY user, but will accept the message and in [RFC2821], means "Cannot VRFY user, but will accept the message
attempt the delivery". Response code 550, also defined in [RFC2821], and attempt the delivery". Response code 550, also defined in
means "Requested action not taken: mailbox unavailable". When the [RFC2821], means "Requested action not taken: mailbox unavailable".
server supports enhanced mail system status codes [RFC3463], the When the server supports enhanced mail system status codes [RFC3463],
enhanced response code as specified below is used. Using the the enhanced response code as specified below is used. Using the
"UTF8REPLY" parameter with a VERIFY (VRFY) or EXPAND (EXPN) command "UTF8REPLY" parameter with a VERIFY (VRFY) or EXPAND (EXPN) command
enables UTF-8 replies for that command only. enables UTF-8 replies for that command only.
If a normal success response (i.e., 250) is returned, the response If a normal success response (i.e., 250) is returned, the response
MAY include the full name of the user and MUST include the mailbox of MAY include the full name of the user and MUST include the mailbox of
the user. It MUST be in either of the following forms: the user. It MUST be in either of the following forms:
User Name <uMailbox> User Name <uMailbox>
; uMailbox is defined in section 3.3 of this document ; uMailbox is defined in Section 3.3 of this document.
; User Name can contain non-ASCII characters. ; User Name can contain non-ASCII characters.
uMailbox uMailbox
; uMailbox is defined in section 3.3 of this document ; uMailbox is defined in Section 3.3 of this document.
If the SMTP reply requires UTF-8 strings, but UTF-8 is not allowed in If the SMTP reply requires UTF-8 strings, but UTF-8 is not allowed in
the reply, and the server supports enhanced mail system status codes the reply, and the server supports enhanced mail system status codes
[RFC3463], the enhanced response code is either "5.6.y" or "2.6.y" [RFC3463], the enhanced response code is either "X.6.8" or "X.6.10"
[SMTP-codes], meaning "A reply containing a UTF-8 string is required [RFC5248], meaning "A reply containing a UTF-8 string is required to
to show the mailbox name, but that form of response is not permitted show the mailbox name, but that form of response is not permitted by
by the client". the client".
If the SMTP Client does not support the UTF8SMTP extension, but If the SMTP client does not support the UTF8SMTP 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 crash. report the reply to the user, and some clients might crash.
Internationalized messages in replies are only allowed in the Internationalized messages in replies are only allowed in the
commands under the situations described above. Under any other commands under the situations described above. Under any other
circumstances, UTF-8 text MUST NOT appear in the reply. circumstances, UTF-8 text MUST NOT appear in the reply.
Although UTF-8 is needed to represent email addresses in responses Although UTF-8 is needed to represent email addresses in responses
under the rules specified in this section, this extension does not under the rules specified in this section, this extension does not
permit the use of UTF-8 for any other purposes. SMTP servers MUST permit the use of UTF-8 for any other purposes. SMTP servers MUST
NOT include non-ASCII characters in replies except in the limited NOT include non-ASCII characters in replies except in the limited
cases specifically permitted in this section. cases specifically permitted in this section.
skipping to change at page 15, line 15 skipping to change at page 15, line 18
Internationalized messages in replies are only allowed in the Internationalized messages in replies are only allowed in the
commands under the situations described above. Under any other commands under the situations described above. Under any other
circumstances, UTF-8 text MUST NOT appear in the reply. circumstances, UTF-8 text MUST NOT appear in the reply.
Although UTF-8 is needed to represent email addresses in responses Although UTF-8 is needed to represent email addresses in responses
under the rules specified in this section, this extension does not under the rules specified in this section, this extension does not
permit the use of UTF-8 for any other purposes. SMTP servers MUST permit the use of UTF-8 for any other purposes. SMTP servers MUST
NOT include non-ASCII characters in replies except in the limited NOT include non-ASCII characters in replies except in the limited
cases specifically permitted in this section. cases specifically permitted in this section.
[[anchor11: RFC Editor: please insert the proper error codes for
"5.6.y" and "2.6.y" after IANA has made the relevant assignments.]]
4. IANA Considerations 4. IANA Considerations
IANA is requested to add a new value "UTF8SMTP" to the SMTP Service IANA has added a new value "UTF8SMTP" to the SMTP Service Extension
Extension subregistry of the Mail Parameters registry, according to subregistry of the Mail Parameters registry, according to the
the following data: following data:
+----------+---------------------------------+-----------+ +----------+---------------------------------+-----------+
| Keywords | Description | Reference | | Keywords | Description | Reference |
+----------+---------------------------------+-----------+ +----------+---------------------------------+-----------+
| UTF8SMTP | Internationalized email address | [RFCXXXX] | | UTF8SMTP | Internationalized email address | [RFC5336] |
+----------+---------------------------------+-----------+ +----------+---------------------------------+-----------+
This document adds new values to the SMTP Enhanced Status Code This document adds new values to the SMTP Enhanced Status Code
subregistry of the Mail Parameters registry, following the guidance subregistry of the Mail Parameters registry, following the guidance
in Section 3.5 and Section 3.7.4.2 of this document, and being based in Sections 3.5 and 3.7.4.2 of this document, and being based on
on [SMTP-codes]. The registration data is as follows: [RFC5248]. The registration data is as follows:
Code: 5.6.x Code: X.6.7
Sample Text: The ALT-ADDRESS is required but not specified Sample Text: The ALT-ADDRESS is required but not specified
Associated basic status code: 553, 550 Associated basic status code: 553, 550
Description: This indicates the reception of a MAIL or RCPT Description: This indicates the reception of a MAIL or RCPT
commands that required an ALT-ADDRESS parameter command that required an ALT-ADDRESS parameter
but such parameter was not present. but such parameter was not present.
Defined: RFC XXXX. (Experimental track) Defined: RFC 5336 (Experimental track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: IESG.
Code: 5.6.y Code: X.6.8
Sample Text: UTF-8 string reply is required, Sample Text: UTF-8 string reply is required,
but not permitted by the client but not permitted by the client
Associated basic status code: 553, 550 Associated basic status code: 553, 550
Description: This indicates that a reply containing a UTF-8 Description: This indicates that a reply containing a UTF-8
string is required to show the mailbox name, string is required to show the mailbox name,
but that form of response is not but that form of response is not
permitted by the client permitted by the client.
Defined: RFC XXXX. (Experimental track) Defined: RFC 5336. (Experimental track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: IESG.
Code: 5.6.z Code: X.6.9
Sample Text: UTF8SMTP downgrade failed Sample Text: UTF8SMTP downgrade failed
Associated basic status code: 550 Associated basic status code: 550
Description: This indicates that transaction failed Description: This indicates that transaction failed
after the final "." of the DATA command after the final "." of the DATA command.
Defined: RFC XXXX. (Experimental track) Defined: RFC 5336. (Experimental track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: IESG.
Code: 2.6.y Code: X.6.10
Sample Text: UTF-8 string reply is required, Sample Text: UTF-8 string reply is required,
but not permitted by the client but not permitted by the client
Associated basic status code: 252 Associated basic status code: 252
Description: This indicates that a reply containing a UTF-8 Description: This indicates that a reply containing a UTF-8
string is required to show the mailbox name, string is required to show the mailbox name,
but that form of response is not but that form of response is not
permitted by the client permitted by the client.
Defined: RFC XXXX. (Experimental track) Defined: RFC 5336. (Experimental track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: IESG.
The "Mail Transmission Types" registry under Mail Parameters registry The "Mail Transmission Types" registry under the Mail Parameters
is requested to be updated to include the following new entries: registry is requested to be updated to include the following new
entries:
+---------------+----------------------------+----------------------+ +---------------+----------------------------+----------------------+
| WITH protocol | Description | Reference | | WITH protocol | Description | Reference |
| types | | | | types | | |
+---------------+----------------------------+----------------------+ +---------------+----------------------------+----------------------+
| UTF8SMTP | UTF8SMTP with Service | [RFCXXXX] | | UTF8SMTP | UTF8SMTP with Service | [RFC5336] |
| | Extensions | | | | Extensions | |
| UTF8SMTPA | UTF8SMTP with SMTP AUTH | [RFC4954] [RFCXXXX] | | UTF8SMTPA | UTF8SMTP with SMTP AUTH | [RFC4954] [RFC5336] |
| UTF8SMTPS | UTF8SMTP with STARTTLS | [RFC3207] [RFCXXXX] | | UTF8SMTPS | UTF8SMTP with STARTTLS | [RFC3207] [RFC5336] |
| UTF8SMTPSA | UTF8SMTP with both | [RFC3207] [RFC4954] | | UTF8SMTPSA | UTF8SMTP with both | [RFC3207] [RFC4954] |
| | STARTTLS and SMTP AUTH | [RFCXXXX] | | | STARTTLS and SMTP AUTH | [RFC5336] |
+---------------+----------------------------+----------------------+ +---------------+----------------------------+----------------------+
5. Security Considerations 5. Security Considerations
See the extended security considerations discussion in the framework See the extended security considerations discussion in the framework
document [RFC4952]. document [RFC4952].
6. Acknowledgements 6. Acknowledgements
Much of the text in the initial version of this specification was Much of the text in the initial version of this specification was
derived or copied from [Klensin-emailaddr] with the permission of the derived or copied from [Emailaddr] with the permission of the author.
author. Significant comments and suggestions were received from Significant comments and suggestions were received from Xiaodong LEE,
Xiaodong LEE, Nai-Wen Hsu, Yangwoo KO, Yoshiro YONEYA, and other Nai-Wen Hsu, Yangwoo KO, Yoshiro YONEYA, and other members of the JET
members of the JET team and were incorporated into the specification. team and were incorporated into the specification. Additional
Additional important comments and suggestions, and often specific important comments and suggestions, and often specific text, were
text, were contributed by many members of the WG and design team. contributed by many members of the WG and design team. Those
Those contributions include material from John C Klensin, Charles contributions include material from John C Klensin, Charles Lindsey,
Lindsey, Dave Crocker, Harald Tveit Alvestrand, Marcos Sanz, Chris Dave Crocker, Harald Tveit Alvestrand, Marcos Sanz, Chris Newman,
Newman, Martin Duerst, Edmon Chung, Tony Finch, Kari Hurtta, Randall Martin Duerst, Edmon Chung, Tony Finch, Kari Hurtta, Randall Gellens,
Gellens, Frank Ellermann, Alexey Melnikov, Pete Resnick, S. Frank Ellermann, Alexey Melnikov, Pete Resnick, S. Moonesamy, Soobok
Moonesamy, Soobok Lee, Shawn Steele, Alfred Hoenes Miguel Garcia, Lee, Shawn Steele, Alfred Hoenes, Miguel Garcia, Magnus Westerlund,
Magnus Westerlund and Lars Eggert. Of course, none of the and Lars Eggert. Of course, none of the individuals are necessarily
individuals are necessarily responsible for the combination of ideas responsible for the combination of ideas represented here.
represented here.
7. Change History
[[anchor15: RFC Editor: Please remove this section.]]
7.1. draft-ietf-eai-smtpext: Version 00
This version supercedes draft-yao-ima-smtpext-03.txt. It refines the
ABNF definition of the internationalized email address. It
represents as the EAI working group document.
7.2. draft-ietf-eai-smtpext: Version 01
o Upgraded to reflect discussions during IETF 66.
o Remove the atomic parameter.
o Add the new section of "the Suggestion of the value of the ALT-
ADDRESS parameter".
7.3. draft-ietf-eai-smtpext: Version 02
o Upgraded to reflect the recent discussion of the ima@ietf.org
mailing list.
o Add the section of "Body Parts and SMTP Extensions".
o Add the new section of "Change History".
o Add the subsection about SMTP extensions for DSN.
7.4. draft-ietf-eai-smtpext: Version 03
o Update the syntax related to mailbox.
o Update the trace field section.
o Add the new section about message retry.
o Update the subsection about SMTP extensions for DSN.
7.5. draft-ietf-eai-smtpext: Version 04
o Refine some syntax.
o Delete "Message Header Label" section.
o Change "bounce" to "reject".
7.6. draft-ietf-eai-smtpext: Version 05
o Refine the abstract.
o Delete "The Suggestion of the Value of the ALT-ADDRESS parameter"
section.
o Move original section 2.7.4 and 2.7.5 to section 3 with the name
"Issues with other parts of the email system".
o Add the new section "LMTP".
o Refine some text according to suggestions from the EAI mailing
list discussion
o Remove the section "Mailing List Question"
7.7. draft-ietf-eai-smtpext: Version 06
o Delete the section about message retry.
o Add the new subsection about Mail eXchangers
o Add the new section about "UTF-8 Reply"
o Refine some response code for the section "Using the ALT-ADDRESS
parameter"
7.8. draft-ietf-eai-smtpext: Version 07
o Rename the section 2.5
o Refine the section 2.7
7.9. draft-ietf-eai-smtpext: Version 08
o Refine some texts and update some references
7.10. draft-ietf-eai-smtpext: Version 09
o Add the appendix
o Move section 3.1, 3.2 and section 5 to Appendix
o Remove section 3.3 and section 4
o Add the new term definitions of conventional message and
international message in the appendix
o Refine some texts according to suggestions from the EAI mailing
list discussion during WG Last call
o Use the same reference for ASCII as RFC 2821.
o General editorial revision and cleanup, including extensive
modifications to the XML to produce a version that has better odds
of getting through the various checkers and validators.
7.11. draft-ietf-eai-smtpext: Version 10
o Refine the text
o Add some text about "ALT-ADDRESS" in the section 2.4
o Add the appendix A.5
7.12. draft-ietf-eai-smtpext: Version 11
o Refine the text
o Reference updating
7.13. draft-ietf-eai-smtpext: Version 12
o Remove the section 1.2 about Proposal Context and merge the text
into new section 2
o Add the new section 2 about overview of operation
o Update the IANA consideration
o Refine the text
7.14. draft-ietf-eai-smtpext: Version 13
o Update the Abstract
o Refine the syntax about the equivalent of import clause
8. References 7. References
8.1. Normative References 7.1. 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.
[EAI-dsn] Newman, C. and A. Melnikov, "SMTP extensions for DSNs",
draft-ietf-eai-dsn-06.txt (work in progress),
January 2008.
[EAI-utf8header]
Abel, Y., "Transmission of Email Headers in UTF-8
Encoding", draft-ietf-eai-utf8headers-12.txt (work in
progress), July 2008.
[RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. [RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
Crocker, "SMTP Service Extension for 8bit-MIMEtransport", Crocker, "SMTP Service Extension for 8bit-
RFC 1652, July 1994. MIMEtransport", RFC 1652, July 1994.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001. April 2001.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001. April 2001.
[RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service [RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP)
Extension for Delivery Status Notifications (DSNs)", Service Extension for Delivery Status Notifications
RFC 3461, January 2003. (DSNs)", RFC 3461, January 2003.
[RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes", [RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes",
RFC 3463, January 2003. RFC 3463, January 2003.
[RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format [RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message
for Delivery Status Notifications", RFC 3464, Format for Delivery Status Notifications", RFC 3464,
January 2003. January 2003.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)", "Internationalizing Domain Names in Applications
RFC 3490, March 2003. (IDNA)", RFC 3490, March 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail", [RFC4409] Gellens, R. and J. Klensin, "Message Submission for
RFC 4409, April 2006. Mail", RFC 4409, April 2006.
[RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for [RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007. Internationalized Email", RFC 4952, July 2007.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[SMTP-codes] [RFC5248] Hansen, T. and J. Klensin, "A Registry for SMTP
Hansen , T. and J. Klensin, "A Registry for SMTP Enhanced Enhanced Mail System Status Codes", BCP 138, RFC 5248,
Mail System Status Codes", June 2008.
draft-hansen-4468upd-mailesc-registry-03 (work in
progress), January 2008.
8.2. Informative References [RFC5335] Abel, Y., Ed., "Internationalized Email Headers",
RFC 5335, September 2008.
[EAI-downgrading] [RFC5337] Newman, C. and A. Melnikov, Ed., "Internationalized
YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading Delivery Status and Disposition Notifications",
mechanism for Internationalized eMail Address", RFC 5337, September 2008.
draft-ietf-eai-downgrade-07 (work in progress), 3 2008.
[Klensin-emailaddr] 7.2. Informative References
Klensin, J., "Internationalization of Email Addresses",
draft-klensin-emailaddr-i18n-03 (work in progress), [Downgrade] Fujiwara, K. and Y. Yoneya, "Downgrading mechanism for
July 2005. Email Address Internationalization", Work in Progress,
July 2008.
[Emailaddr] Klensin, J., "Internationalization of Email Addresses",
Work in Progress, July 2005.
[RFC0974] Partridge, C., "Mail routing and the domain system", [RFC0974] Partridge, C., "Mail routing and the domain system",
RFC 974, January 1986. RFC 974, January 1986.
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033, [RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033,
October 1996. October 1996.
[RFC2821bis] [RFC2821bis] Klensin, J., "Simple Mail Transfer Protocol", Work
Klensin, J., "Simple Mail Transfer Protocol", in Progress, July 2008.
draft-klensin-rfc2821bis-10 (work in progress), 4 2008.
[RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission [RFC3030] Vaudreuil, G., "SMTP Service Extensions for
of Large and Binary MIME Messages", RFC 3030, Transmission of Large and Binary MIME Messages",
December 2000. RFC 3030, December 2000.
[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over [RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP
Transport Layer Security", RFC 3207, February 2002. over Transport Layer Security", RFC 3207,
February 2002.
[RFC4954] Siemborski, R. and A. Melnikov, "SMTP Service Extension [RFC4954] Siemborski, R., Ed. and A. Melnikov, Ed., "SMTP Service
for Authentication", RFC 4954, July 2007. Extension for Authentication", RFC 4954, July 2007.
Appendix A. Material Updating RFC 4952 Appendix A. Material Updating RFC 4952
RFC 4952, the Overview and Framework document covering this set of RFC 4952, the overview and framework document covering this set of
extensions for internationalized email [RFC4952], was completed extensions for internationalized email, was completed before this
before this specification, which specifies a particular part of the specification, which specifies a particular part of the protocol set.
protocol set. This appendix, which is normative, contains material This appendix, which is normative, contains material that would have
that would have been incorporated into RFC 4952 had it been delayed been incorporated into RFC 4952 had it been delayed until the work
until the work described in the rest of this specification was described in the rest of this specification was completed. This
completed and that should be included in any update to RFC 4952. material should be included in any update to RFC 4952.
A.1. Conventional Message and Internationalized Message A.1. Conventional Message and Internationalized Message
o A conventional message is one that does not use any extension o A conventional message is one that does not use any extension
defined in this document or in the UTF8header specification defined in this document or in the UTF-8 header specification
[EAI-utf8header], and which is strictly conformant to RFC 2822 [RFC5335], and which is strictly conformant to RFC 2822 [RFC2822].
[RFC2822].
o An internationalized message is a message utilizing one or more of o An internationalized message is a message utilizing one or more of
the extensions defined in this specification or in the UTF8header the extensions defined in this specification or in the UTF-8
specification [EAI-utf8header], so that it is no longer conformant header specification [RFC5335], so that it is no longer conformant
to the RFC 2822 specification of a message. to the RFC 2822 specification of a message.
A.2. LMTP A.2. LMTP
LMTP [RFC2033] may be used as the final delivery agent. In such LMTP [RFC2033] may be used as the final delivery agent. In such
cases, LMTP may be arranged to deliver the mail to the mail store. cases, LMTP may be arranged to deliver the mail to the mail store.
The mail store may not have UTF8SMTP capability. LMTP need to be The mail store may not have UTF8SMTP capability. LMTP needs to be
updated to deal with these situations. updated to deal with these situations.
A.3. SMTP Service Extension for DSNs A.3. SMTP Service Extension for DSNs
The existing draft standard Delivery status notifications (DSNs) The existing Draft Standard regarding delivery status notifications
[RFC3461] is limited to ASCII text in the machine readable portions (DSNs) [RFC3461] is limited to ASCII text in the machine readable
of the protocol. "International Delivery and Disposition portions of the protocol. "International Delivery Status and
Notifications" [EAI-dsn] adds a new address type for international Disposition Notifications" [RFC5337] adds a new address type for
email addresses so an original recipient address with non-ASCII international email addresses so an original recipient address with
characters can be correctly preserved even after downgrading. If an non-ASCII characters can be correctly preserved even after
SMTP server advertises both the UTF8SMTP and the DSN extension, that downgrading. If an SMTP server advertises both the UTF8SMTP and the
server MUST implement EAI-dsn [EAI-dsn] including support for the DSN extension, that server MUST implement EAI DSN [RFC5337] including
ORCPT parameter. support for the ORCPT parameter.
A.4. Implementation Advice A.4. Implementation Advice
In the absence of this extension, SMTP clients and servers are In the absence of this extension, SMTP clients and servers are
constrained to using only those addresses permitted by RFC 2821. The constrained to using only those addresses permitted by RFC 2821. The
local parts of those addresses MAY be made up of any ASCII local parts of those addresses MAY be made up of any ASCII
characters, although some of them MUST be quoted as specified there. characters, although some of them MUST be quoted as specified there.
It is notable in an internationalization context that there is a long It is notable in an internationalization context that there is a long
history on some systems of using overstruck ASCII characters (a history on some systems of using overstruck ASCII characters (a
character, a backspace, and another character) within a quoted string character, a backspace, and another character) within a quoted string
to approximate non-ASCII characters. This form of to approximate non-ASCII characters. This form of
internationalization SHOULD be phased out as this extension becomes internationalization SHOULD be phased out as this extension becomes
widely deployed but backward-compatibility considerations require widely deployed, but backward-compatibility considerations require
that it continue to be supported. that it continue to be supported.
A.5. Applicability of SMTP Extension to Additional Uses A.5. Applicability of SMTP Extension to Additional Uses
Among other protocol changes, the SMTP extension allows an optional Among other protocol changes, the SMTP extension allows an optional
alternate address to be supplied with the MAIL and RCPT commands. alternate address to be supplied with the MAIL and RCPT commands.
For the purposes of this set of specifications, this alternate For the purposes of this set of specifications, this alternate
address only has meaning when the primary address contains UTF-8 address only has meaning when the primary address contains UTF-8
characters and the message is downgraded. While it may be tempting characters and the message is downgraded. While it may be tempting
to consider the alternate address as a general-purpose second-chance to consider the alternate address as a general-purpose second-chance
address, to be used whenever the primary address is rejected, such address to be used whenever the primary address is rejected, such
behavior is not defined here. This restriction allows for future behavior is not defined here. This restriction allows for future
extensions to be developed which create such a general-purpose extensions to be developed which create such a general-purpose
second-chance address, although no specific work on such an extension second-chance address, although no specific work on such an extension
is currently anticipated. Note that any such extension needs to is currently anticipated. Note that any such extension needs to
consider the question of what the [RFC0974] sequencing rules mean consider the question of what the [RFC0974] sequencing rules mean
when different possible servers support different sets of ESMTP when different possible servers support different sets of ESMTP
options (or, in this case, addresses). The answer to this question options (or, in this case, addresses). The answer to this question
may also imply updates to [RFC2821]. may also imply updates to [RFC2821].
Authors' Addresses Authors' Addresses
Jiankang YAO (editor) Jiankang YAO (editor)
CNNIC CNNIC
No.4 South 4th Street, Zhongguancun No.4 South 4th Street, Zhongguancun
Beijing Beijing
Phone: +86 10 58813007 Phone: +86 10 58813007
Email: yaojk@cnnic.cn EMail: yaojk@cnnic.cn
Wei MAO (editor) Wei MAO (editor)
CNNIC CNNIC
No.4 South 4th Street, Zhongguancun No.4 South 4th Street, Zhongguancun
Beijing Beijing
Phone: +86 10 58812230 Phone: +86 10 58812230
Email: maowei_ietf@cnnic.cn EMail: maowei_ietf@cnnic.cn
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
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