draft-ietf-eai-smtpext-11.txt   draft-ietf-eai-smtpext-12.txt 
Network Working Group J. Yao, Ed. Network Working Group J. Yao, Ed.
Internet-Draft W. Mao, Ed. Internet-Draft W. Mao, Ed.
Updates: RFC4952 CNNIC Updates: RFC4952, 2821 and 2822 CNNIC
(if approved) January 28, 2008 (if approved) April 8, 2008
Intended status: Experimental Intended status: Experimental
Expires: July 31, 2008 Expires: October 10, 2008
SMTP extension for internationalized email address SMTP extension for internationalized email address
draft-ietf-eai-smtpext-11.txt draft-ietf-eai-smtpext-12.txt
Status of this Memo Status of this Memo
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This Internet-Draft will expire on July 31, 2008. This Internet-Draft will expire on October 10, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
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. specification is specified in another document.
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. Proposal Context . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 4
2. Mail Transport-level Protocol . . . . . . . . . . . . . . . . 4 3. Mail Transport-level Protocol . . . . . . . . . . . . . . . . 4
2.1. Framework for the Internationalization Extension . . . . . 4 3.1. Framework for the Internationalization Extension . . . . . 4
2.2. The UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5 3.2. The UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5
2.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 6 3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7
2.4. The ALT-ADDRESS Parameter . . . . . . . . . . . . . . . . 8 3.4. The ALT-ADDRESS Parameter . . . . . . . . . . . . . . . . 8
2.5. ALT-ADDRESS Parameter Usage and Response Codes . . . . . . 9 3.5. ALT-ADDRESS Parameter Usage and Response Codes . . . . . . 9
2.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 10 3.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 10
2.7. Additional ESMTP Changes and Clarifications . . . . . . . 11 3.7. Additional ESMTP Changes and Clarifications . . . . . . . 11
2.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 11 3.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 11
2.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 11 3.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 11
2.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11 3.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11
2.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 12 3.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 12
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
4. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
6. Change History . . . . . . . . . . . . . . . . . . . . . . . . 15 7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 15 7.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 17
6.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 16 7.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 17
6.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 16 7.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 17
6.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 16 7.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 17
6.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 16 7.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 17
6.6. draft-ietf-eai-smtpext: Version 05 . . . . . . . . . . . . 16 7.6. draft-ietf-eai-smtpext: Version 05 . . . . . . . . . . . . 17
6.7. draft-ietf-eai-smtpext: Version 06 . . . . . . . . . . . . 16 7.7. draft-ietf-eai-smtpext: Version 06 . . . . . . . . . . . . 18
6.8. draft-ietf-eai-smtpext: Version 07 . . . . . . . . . . . . 17 7.8. draft-ietf-eai-smtpext: Version 07 . . . . . . . . . . . . 18
6.9. draft-ietf-eai-smtpext: Version 08 . . . . . . . . . . . . 17 7.9. draft-ietf-eai-smtpext: Version 08 . . . . . . . . . . . . 18
6.10. draft-ietf-eai-smtpext: Version 09 . . . . . . . . . . . . 17 7.10. draft-ietf-eai-smtpext: Version 09 . . . . . . . . . . . . 18
6.11. draft-ietf-eai-smtpext: Version 10 . . . . . . . . . . . . 17 7.11. draft-ietf-eai-smtpext: Version 10 . . . . . . . . . . . . 18
6.12. draft-ietf-eai-smtpext: Version 11 . . . . . . . . . . . . 17 7.12. draft-ietf-eai-smtpext: Version 11 . . . . . . . . . . . . 18
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.13. draft-ietf-eai-smtpext: Version 12 . . . . . . . . . . . . 19
7.1. Normative References . . . . . . . . . . . . . . . . . . . 17 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2. Informative References . . . . . . . . . . . . . . . . . . 19 8.1. Normative References . . . . . . . . . . . . . . . . . . . 19
Appendix A. Material Updating RFC 4952 . . . . . . . . . . . . . 19 8.2. Informative References . . . . . . . . . . . . . . . . . . 20
A.1. Conventional Message and Internationalized Message . . . . 19 Appendix A. Material Updating RFC 4952 . . . . . . . . . . . . . 21
A.2. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 A.1. Conventional Message and Internationalized Message . . . . 21
A.3. SMTP Service Extension for DSNs . . . . . . . . . . . . . 20 A.2. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
A.4. Implementation Advice . . . . . . . . . . . . . . . . . . 20 A.3. SMTP Service Extension for DSNs . . . . . . . . . . . . . 21
A.5. Applicability of SMTP Extension to Additional Uses . . . . 20 A.4. Implementation Advice . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 A.5. Applicability of SMTP Extension to Additional Uses . . . . 22
Intellectual Property and Copyright Statements . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
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 up those names in their own tables. In addition to this, the simple
extended email transport protocol [RFC2821] provides a negotiation mail transfer protocol [RFC2821] provides a negotiation mechanism
mechanism with which clients can discover server capabilities and about service extension with which clients can discover server
make decisions for further processing. An extended overview of the capabilities and make decisions for further processing. An extended
extension model for internationalized addresses and headers appears overview of the extension model for internationalized addresses and
in [EAI-framework], referred to as "the framework document" or just headers appears in [RFC4952], referred to as "the framework document"
as "Framework" elsewhere in this specification. This document or just as "Framework" elsewhere in this specification. This
specifies an SMTP extension to permit internationalized email document specifies an SMTP extension to permit internationalized
addresses in envelopes, and UNICODE characters (encoded in UTF-8) in email addresses in envelopes, and UNICODE characters (encoded 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.
1.2. Proposal Context 1.2. Terminology
This specification describes an optional extension to the email
transport mechanism that permits non-ASCII [ASCII] characters in both
the envelope and header fields of messages. The EAI-utf8header
specification [EAI-utf8header] provides the details of how and where
non-ASCII characters are permitted in the header fields of messages.
The context for the change is described in the framework document.
1.3. Terminology
The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
and "MAY" in this specification are to be interpreted as described in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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 one.
This specification defines only those ABNF [RFC4234] syntax rules This specification defines only those Augmented BNF for Syntax
that are different from those of the base email specifications Specifications (ABNF) [RFC5234] syntax rules that are different from
[RFC2821][RFC2822] and, where the earlier rules are upgraded or those of the base email specifications [RFC2821][RFC2822] and, where
extended, gives them new names. When the new rule is a small the earlier rules are upgraded or extended, gives them new names.
modification to the older one, it is typically given a name starting When the new rule is a small modification to the older one, it is
with "u". Rules that are undefined here may be found in the base typically given a name starting with "u". Rules that are undefined
email specifications under the same names. here may be found in the base email specifications under the same
names.
[[anchor4: NOTE TO RFC EDITOR: Please remove the following text [[anchor3: NOTE TO RFC EDITOR: Please remove the following text
before publication.]] before publication.]]
This specification is being discussed on the EAI mailing list. See This specification is being discussed on the EAI mailing list. See
https://www1.ietf.org/mailman/listinfo/ima for information about https://www1.ietf.org/mailman/listinfo/ima for information about
subscribing. The list's archive is at subscribing. The list's archive is at
http://www1.ietf.org/mail-archive/web/ima/index.html. http://www1.ietf.org/mail-archive/web/ima/index.html.
2. Mail Transport-level Protocol 2. Overview of Operation
2.1. Framework for the Internationalization Extension This specification describes an optional extension to the email
transport mechanism that permits non-ASCII [ASCII] characters in both
the envelope and header fields of messages, which are encoded with
UTF-8 [RFC3629] characters. The extension is identified with the
token "UTF8SMTP". In order to provide information that may be needed
in downgrading, an optional alternate ASCII address may be needed if
an SMTP client attempts to transfer an internationalized message and
encounters a server that does not support this extension.
The EAI-utf8header specification [EAI-utf8header] provides the
details of how and where non-ASCII characters are permitted in the
header fields of messages. The context for this specification is
described in the framework document.
3. Mail Transport-level Protocol
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 [EAI-framework] and the use of this parameter appears in [RFC4952] and
[EAI-downgrading]. [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).
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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 9. The mail message body is extended as specified in
[EAI-utf8header]. [EAI-utf8header].
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].
2.2. 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 MTA. Any
domain names that are to be looked up in the DNS MUST first be domain names that are to be looked up in the DNS MUST first be
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ToASCII() operation unless they are already in that form. Any domain ToASCII() operation unless they are already in that form. Any domain
names that are to be compared to local strings SHOULD be checked for names that are to be compared to local strings SHOULD be checked for
validity and then MUST be compared as specified in section 3.4 of validity and then MUST be compared as specified in section 3.4 of
IDNA. 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 [EAI-utf8header] (which may also include mailbox names
in UTF-8). It MAY transmit the domain parts of mailbox names within in UTF-8). It MAY transmit the domain parts of mailbox names within
SMTP commands or the message header in either the form of ACE labels SMTP commands or the message header in either the form of ACE (ASCII
as specified in IDNA [RFC3490] or as UTF-8 strings. All labels in Compatible Encoding) labels as specified in IDNA [RFC3490] or as
domain parts of mailbox names which are IDNs (either UTF-8 or ACE UTF-8 strings. All labels in domain parts of mailbox names which are
strings) MUST be valid. If the original client submits a message to IDNs (either UTF-8 or ACE strings) MUST be valid. If the original
a Message Submission Server ("MSA") [RFC4409], it is the client submits a message to a Message Submission Server ("MSA")
responsibility of the MSA that all domain labels are valid; otherwise [RFC4409], it is the responsibility of the MSA that all domain labels
it is the original client's responsibility. The presence of the are valid; otherwise it is the original client's responsibility. The
UTF8SMTP extension does not change the requirement of RFC 2821 that presence of the UTF8SMTP extension does not change the requirement of
servers relaying mail MUST NOT attempt to parse, evaluate, or RFC 2821 that servers relaying mail MUST NOT attempt to parse,
transform the local part in any way. evaluate, or 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 (For this
paragraph, the internationalized domain name in the form of ACE 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".) and MUST NOT transmit a mail message containing
internationalized mail headers as described in [EAI-utf8header] at internationalized mail headers as described in [EAI-utf8header] at
any level within its MIME structure. Instead, if an SMTP client any level within its MIME structure. Instead, if an SMTP client
(SMTP sender) attempts to transfer a internationalized message and (SMTP sender) attempts to transfer an internationalized message and
encounters a server that does not support the extension, it MUST make encounters a server that does not support the extension, it MUST make
one of the following four choices: 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 2. Either reject the message during the SMTP transaction or accept
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being attempted, downgrade the message to an all-ASCII form as being attempted, downgrade the message to an all-ASCII form as
specified in [EAI-downgrading]. An ASCII address is considered specified in [EAI-downgrading]. 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 constrained by Message Submission [RFC4409], while "choice 4" is is constrained by Message Submission [RFC4409], while "choice 4" is
constrained by [EAI-downgrading]. constrained by [EAI-downgrading].
2.3. 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 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
skipping to change at page 7, line 14 skipping to change at page 7, line 23
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
[RFC4234] as [RFC5234] as
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
; Replace character in RFC 2821, section 4.1.2
; atext is defined in RFC 2822 ; atext is defined in 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 is Double Quote defined in RFC 4234 ; DQUOTE is Double Quote defined in RFC 5234
uqcontent = qcontent / UTF8-non-ascii uqcontent = qcontent / UTF8-non-ascii
; qcontent is defined in RFC 2822, section 3.2.5 ; qcontent is defined in RFC 2822, section 3.2.5
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 is defined in RFC2821 section 4.1.2 ; address-literal is defined in RFC2821 section 4.1.2
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 is defined in RFC 2821, section 4.1.3 ; Let-dig is defined in RFC 2821, section 4.1.3
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
skipping to change at page 8, line 17 skipping to change at page 8, line 21
uLet-dig = Let-dig / UTF8-non-ascii uLet-dig = Let-dig / UTF8-non-ascii
; Let-dig is defined in RFC 2821, section 4.1.3 ; Let-dig is defined in RFC 2821, section 4.1.3
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, UTF8-3 and UTF8-4 are two, three, or four ; UTF8-2, UTF8-3 and UTF8-4 are two, three, or four
; octet UTF-8 characters, as defined in RFC 3629 ; octet UTF-8 characters, as defined in 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.
2.4. 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
which may be used when downgrading. If the ALT-ADDRESS esmtp-keyword which may be used when downgrading. If the ALT-ADDRESS esmtp-keyword
is used, it MUST have an associated esmtp-value (ALT-ADDRESS-esmtp- is 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,
skipping to change at page 9, line 11 skipping to change at page 9, line 17
; 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 2.3 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
; A-d-l is defined in RFC 2821, section 4.1.2 ; A-d-l is defined in RFC 2821, section 4.1.2
; uMailbox is defined in section 2.3 of this document ; uMailbox is defined in section 3.3 of this document
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 is defined in RFC 3461, section 4.2 ; xtext is defined in RFC 3461, section 4.2
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.
2.5. 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
lacks ALT-ADDRESSes as discussed in Section 2.2 of this lacks ALT-ADDRESSes as discussed in Section 3.2 of this
specification. specification.
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 "5.6.x" [SMTP-codes] is used, meaning that "The ALT-ADDRESS is
required but not specified". required 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 "5.6.z" [SMTP-codes] is used,
meaning that "UTF8SMTP downgrade failed". meaning that "UTF8SMTP downgrade failed".
[[anchor7: RFC Editor: please insert the proper error codes for [[anchor6: RFC Editor: please insert the proper error codes for
"5.6.x" and "5.6.z" after IANA has made the relevant assignments.]] "5.6.x" and "5.6.z" after IANA has made the relevant assignments.]]
2.6. 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
capability for 8-bit data and to avoid a number of complex encoding capability for 8-bit data and to avoid a number of complex encoding
problems, the use of internationalized addresses obviously does not problems, the use of internationalized addresses obviously does not
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, if the server advertises appropriate given the body content or, with the BODY=BINARYMIME
BINARYMIME [RFC3030] and the BODY=BINARYMIME is appropriate, with the parameter, if the server advertises BINARYMIME [RFC3030] and that is
BODY=BINARYMIME parameter. 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.
2.7. 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 contexts in addition to addresses ("mailboxes") and domain names in various contexts in
the MAIL and RCPT commands and extended alternatives to them. In addition to the MAIL and RCPT commands and extended alternatives to
general, the rule is that, when RFC 2821 specifies a mailbox, this them. In general, the rule is that, when RFC 2821 specifies a
specification expects UTF-8 to be used for the entire string; when mailbox, this specification expects UTF-8 to be used for the entire
RFC 2821 specifies a domain name, the name SHOULD be in the form of string; when RFC 2821 specifies a domain name, the name SHOULD be in
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.
2.7.1. 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' reply 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.
2.7.2. 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
more than one server, and may also or instead have an agreement with more than one server, and may also or instead have an agreement with
other organizations to accept mail as a backup. Authorized servers other organizations to accept mail as a backup. Authorized servers
are generally listed in MX records as described in RFC2821. When are generally listed in MX records as described in RFC2821. When
more than one server accepts mail for the domain-part of a mailbox, more than one server accepts mail for the domain-part of a mailbox,
it is strongly advised that either all or none of them support the it is strongly advised that either all or none of them support the
UTF8SMTP extension. Otherwise, surprising downgrades can happen UTF8SMTP extension. Otherwise, surprising downgrades can happen
during temporary failures, which is not a good thing. during temporary failures, which users might perceive as a serious
reliability issue.
2.7.3. 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 RFC2821
; uReverse-path is defined in Section 2.3 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 RFC2821
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 RFC2821
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 RFC2821
; 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 RFC2821
; 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
[[anchor11: Note: The FOR parameter has been changed to match the [[anchor10: Note: The FOR parameter has been changed to match the
definition in RFC2821bis, permitting only one address in the For definition in RFC2821bis, permitting only one address in the For
clause. The group working on that document reached mailing list clause. The group working on that document reached mailing list
consensus that the syntax in RFC 2821 that permitted more than one consensus that the syntax in RFC 2821 that permitted more than one
address was simply a mistake.]] address was simply a mistake.]]
Except in the 'uFor' and 'uReverse-path' line where non-ASCII domain Except in the 'uFor' clause and 'uReverse-path' value where non-ASCII
names may be used, internationalized domain names in Received fields domain names may be used, internationalized domain names in Received
MUST be transmitted in the form of ACE labels. The protocol value of fields MUST be transmitted in the form of ACE labels. The protocol
the WITH clause when this extension is used is one of the UTF8SMTP value of the WITH clause when this extension is used is one of the
values specified in the "IANA Considerations" section of this UTF8SMTP values specified in the "IANA Considerations" section of
document. this document.
2.7.4. UTF-8 Strings in Replies 3.7.4. UTF-8 Strings in Replies
2.7.4.1. MAIL and RCPT Commands 3.7.4.1. MAIL and RCPT Commands
If the client issues the RCPT command containing non-ASCII If the client issues a RCPT command containing non-ASCII characters,
characters, the SMTP server is permitted to use UTF-8 characters in the SMTP server is permitted to use UTF-8 characters in the email
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 replies containing UTF-8 email addresses. If
a given RCPT command does not include a non-ASCII envelope address, a given RCPT command does not include a non-ASCII envelope address,
the server MUST NOT return a 251 or 551 response containing a non- the server MUST NOT return a 251 or 551 response containing a non-
ASCII mailbox. Instead, it MUST transform such responses into 250 or ASCII mailbox. Instead, it MUST transform such responses into 250 or
550 responses that do not contain addresses. 550 responses that do not contain addresses.
2.7.4.2. 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 the 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 which 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 2.3 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 2.3 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 either reply code client does not use the "UTF8REPLY" parameter, then the server MUST
252 or reply code 550 is used. Response code 252, defined in use either the reply code 252 or 550. Response code 252, defined in
[RFC2821], means "Cannot VRFY user, but will accept the message and [RFC2821], means "Cannot VRFY user, but will accept the message and
attempt the delivery". Response code 550, also defined in [RFC2821], attempt the delivery". Response code 550, also defined in [RFC2821],
means "Requested action not taken: mailbox unavailable". When the means "Requested action not taken: mailbox unavailable". When the
server supports enhanced mail system status codes [RFC3463], the server supports enhanced mail system status codes [RFC3463], the
enhanced response code as specified below is used. Using 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 2.3 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 2.3 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 "5.6.y" or "2.6.y"
[SMTP-codes], meaning "A reply containing a UTF-8 string is required [SMTP-codes], meaning "A reply containing a UTF-8 string is required
to show the mailbox name, but that form of response is not permitted to show the mailbox name, but that form of response is not permitted
by the client". by 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
skipping to change at page 14, line 32 skipping to change at page 14, line 41
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.
[[anchor14: RFC Editor: please insert the proper error codes for [[anchor12: RFC Editor: please insert the proper error codes for
"5.6.y" and "2.6.y" after IANA has made the relevant assignments.]] "5.6.y" and "2.6.y" after IANA has made the relevant assignments.]]
3. IANA Considerations 4. IANA Considerations
IANA is requested to add "UTF8SMTP" to the SMTP extensions registry IANA is requested to add a new value "UTF8SMTP" to the SMTP Service
with the entry pointing to this specification for its definition. Extension subregistry of the Mail Parameters registry, according to
the following data:
IANA is requested to assign the proper error codes for "5.6.x", +----------+---------------------------------+-----------+
"5.6.z", "5.6.y" and "2.6.y", following the guidance in Section 2.5, | Keywords | Description | Reference |
and based on [SMTP-codes] and enter them in the appropriate registry. +----------+---------------------------------+-----------+
| UTF8SMTP | Internationalized email address | [RFCXXXX] |
+----------+---------------------------------+-----------+
The "Mail Transmission Types" registry is requested to be updated to This document adds new values to the SMTP Enhanced Status Code
include the following new entries: 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
on [SMTP-codes]. The registration data is as follows:
Code: 5.6.x
Sample Text: The ALT-ADDRESS is required but not specified
Associated basic status code: 553, 550
Description: This indicates the reception of a MAIL or RCPT
commands that required an ALT-ADDRESS parameter
but such parameter was not present.
Defined: RFC XXXX. (Experimental track)
Submitter: Jiankang YAO
Change controller: IESG.
Code: 5.6.y
Sample Text: UTF-8 string reply is required,
but not permitted by the client
Associated basic status code: 553, 550
Description: This indicates that a reply containing a UTF-8
string is required to show the mailbox name,
but that form of response is not
permitted by the client
Defined: RFC XXXX. (Experimental track)
Submitter: Jiankang YAO
Change controller: IESG.
Code: 5.6.z
Sample Text: UTF8SMTP downgrade failed
Associated basic status code: 550
Description: This indicates that transaction failed
after the final "." of the DATA command
Defined: RFC XXXX. (Experimental track)
Submitter: Jiankang YAO
Change controller: IESG.
Code: 2.6.y
Sample Text: UTF-8 string reply is required,
but not permitted by the client
Associated basic status code: 252
Description: This indicates that a reply containing a UTF-8
string is required to show the mailbox name,
but that form of response is not
permitted by the client
Defined: RFC XXXX. (Experimental track)
Submitter: Jiankang YAO
Change controller: IESG.
The "Mail Transmission Types" registry under Mail Parameters 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 | [RFCXXXX] |
| | Extensions | | | | Extensions | |
| UTF8SMTPA | UTF8SMTP with SMTP AUTH | [RFC4954] [RFCXXXX] | | UTF8SMTPA | UTF8SMTP with SMTP AUTH | [RFC4954] [RFCXXXX] |
| UTF8SMTPS | UTF8SMTP with STARTTLS | [RFC3207] [RFCXXXX] | | UTF8SMTPS | UTF8SMTP with STARTTLS | [RFC3207] [RFCXXXX] |
| UTF8SMTPSA | UTF8SMTP with both | [RFC3207] [RFC4954] | | UTF8SMTPSA | UTF8SMTP with both | [RFC3207] [RFC4954] |
| | STARTTLS and SMTP AUTH | [RFCXXXX] | | | STARTTLS and SMTP AUTH | [RFCXXXX] |
+---------------+----------------------------+----------------------+ +---------------+----------------------------+----------------------+
4. Security Considerations 5. Security Considerations
See the extended security considerations discussion in the framework See the extended security considerations discussion in the framework
document [EAI-framework]. document [RFC4952].
5. 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 [Klensin-emailaddr] with the permission of the
author. Significant comments and suggestions were received from author. Significant comments and suggestions were received from
Xiaodong LEE, Nai-Wen Hsu, Yangwoo KO, Yoshiro YONEYA, and other Xiaodong LEE, Nai-Wen Hsu, Yangwoo KO, Yoshiro YONEYA, and other
members of the JET team and were incorporated into the specification. members of the JET team and were incorporated into the specification.
Additional important comments and suggestions, and often specific Additional important comments and suggestions, and often specific
text, were contributed by many members of the WG and design team. text, were contributed by many members of the WG and design team.
Those contributions include material from John C Klensin, Charles Those contributions include material from John C Klensin, Charles
Lindsey, Dave Crocker, Harald Tveit Alvestrand, Marcos Sanz, Chris Lindsey, Dave Crocker, Harald Tveit Alvestrand, Marcos Sanz, Chris
Newman, Martin Duerst, Edmon Chung, Tony Finch, Kari Hurtta, Randall Newman, Martin Duerst, Edmon Chung, Tony Finch, Kari Hurtta, Randall
Gellens, Frank Ellermann, Alexey Melnikov, Pete Resnick, S. Gellens, Frank Ellermann, Alexey Melnikov, Pete Resnick, S.
Moonesamy, and Soobok Lee, Shawn Steele. Of course, none of the Moonesamy, Soobok Lee, Shawn Steele, Alfred Hoenes and Miguel Garcia.
individuals are necessarily responsible for the combination of ideas
represented here.
6. Change History Of course, none of the individuals are necessarily responsible for
the combination of ideas represented here.
[[anchor18: RFC Editor: Please remove this section.]] 7. Change History
6.1. draft-ietf-eai-smtpext: Version 00 [[anchor16: 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 This version supercedes draft-yao-ima-smtpext-03.txt. It refines the
ABNF definition of the internationalized email address. It ABNF definition of the internationalized email address. It
represents as the EAI working group document. represents as the EAI working group document.
6.2. draft-ietf-eai-smtpext: Version 01 7.2. draft-ietf-eai-smtpext: Version 01
o Upgraded to reflect discussions during IETF 66. o Upgraded to reflect discussions during IETF 66.
o Remove the atomic parameter. o Remove the atomic parameter.
o Add the new section of "the Suggestion of the value of the ALT- o Add the new section of "the Suggestion of the value of the ALT-
ADDRESS parameter". ADDRESS parameter".
6.3. draft-ietf-eai-smtpext: Version 02 7.3. draft-ietf-eai-smtpext: Version 02
o Upgraded to reflect the recent discussion of the ima@ietf.org o Upgraded to reflect the recent discussion of the ima@ietf.org
mailing list. mailing list.
o Add the section of "Body Parts and SMTP Extensions". o Add the section of "Body Parts and SMTP Extensions".
o Add the new section of "Change History". o Add the new section of "Change History".
o Add the subsection about SMTP extensions for DSN. o Add the subsection about SMTP extensions for DSN.
6.4. draft-ietf-eai-smtpext: Version 03 7.4. draft-ietf-eai-smtpext: Version 03
o Update the syntax related to mailbox. o Update the syntax related to mailbox.
o Update the trace field section. o Update the trace field section.
o Add the new section about message retry. o Add the new section about message retry.
o Update the subsection about SMTP extensions for DSN. o Update the subsection about SMTP extensions for DSN.
6.5. draft-ietf-eai-smtpext: Version 04 7.5. draft-ietf-eai-smtpext: Version 04
o Refine some syntax. o Refine some syntax.
o Delete "Message Header Label" section. o Delete "Message Header Label" section.
o Change "bounce" to "reject". o Change "bounce" to "reject".
6.6. draft-ietf-eai-smtpext: Version 05 7.6. draft-ietf-eai-smtpext: Version 05
o Refine the abstract. o Refine the abstract.
o Delete "The Suggestion of the Value of the ALT-ADDRESS parameter" o Delete "The Suggestion of the Value of the ALT-ADDRESS parameter"
section. section.
o Move original section 2.7.4 and 2.7.5 to section 3 with the name 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". "Issues with other parts of the email system".
o Add the new section "LMTP". o Add the new section "LMTP".
o Refine some text according to suggestions from the EAI mailing o Refine some text according to suggestions from the EAI mailing
list discussion list discussion
o Remove the section "Mailing List Question" o Remove the section "Mailing List Question"
6.7. draft-ietf-eai-smtpext: Version 06 7.7. draft-ietf-eai-smtpext: Version 06
o Delete the section about message retry. o Delete the section about message retry.
o Add the new subsection about Mail eXchangers o Add the new subsection about Mail eXchangers
o Add the new section about "UTF-8 Reply" o Add the new section about "UTF-8 Reply"
o Refine some response code for the section "Using the ALT-ADDRESS o Refine some response code for the section "Using the ALT-ADDRESS
parameter" parameter"
6.8. draft-ietf-eai-smtpext: Version 07 7.8. draft-ietf-eai-smtpext: Version 07
o Rename the section 2.5 o Rename the section 2.5
o Refine sthe section 2.7 o Refine the section 2.7
6.9. draft-ietf-eai-smtpext: Version 08 7.9. draft-ietf-eai-smtpext: Version 08
o Refine some texts and update some references o Refine some texts and update some references
6.10. draft-ietf-eai-smtpext: Version 09 7.10. draft-ietf-eai-smtpext: Version 09
o Add the appendix o Add the appendix
o Move section 3.1, 3.2 and section 5 to Appendix o Move section 3.1, 3.2 and section 5 to Appendix
o Remove section 3.3 and section 4 o Remove section 3.3 and section 4
o Add the new term definitions of conventional message and o Add the new term definitions of conventional message and
international message in the appendix international message in the appendix
o Refine some texts according to suggestions from the EAI mailing o Refine some texts according to suggestions from the EAI mailing
list discussion during WG Last call list discussion during WG Last call
o Use the same reference for ASCII as RFC 2821. o Use the same reference for ASCII as RFC 2821.
o General editorial revision and cleanup, including extensive o General editorial revision and cleanup, including extensive
modifications to the XML to produce a version that has better odds modifications to the XML to produce a version that has better odds
of getting through the various checkers and validators. of getting through the various checkers and validators.
6.11. draft-ietf-eai-smtpext: Version 10 7.11. draft-ietf-eai-smtpext: Version 10
o Refine the text o Refine the text
o Add some text about "ALT-ADDRESS" in the section 2.4 o Add some text about "ALT-ADDRESS" in the section 2.4
o Add the appendix A.5 o Add the appendix A.5
6.12. draft-ietf-eai-smtpext: Version 11 7.12. draft-ietf-eai-smtpext: Version 11
o Refine the text o Refine the text
o Reference updating o Reference updating
7. References 7.13. draft-ietf-eai-smtpext: Version 12
7.1. Normative References 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
8. 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.
[EAI-dsn] Newman, C. and A. Melnikov, "SMTP extensions for DSNs", [EAI-dsn] Newman, C. and A. Melnikov, "SMTP extensions for DSNs",
draft-ietf-eai-dsn-06.txt (work in progress), draft-ietf-eai-dsn-06.txt (work in progress),
January 2008. January 2008.
[EAI-framework]
Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007.
[EAI-utf8header] [EAI-utf8header]
Abel, Y., "Transmission of Email Headers in UTF-8 Abel, Y., "Transmission of Email Headers in UTF-8
Encoding", draft-ietf-eai-utf8headers-09.txt (work in Encoding", draft-ietf-eai-utf8headers-09.txt (work in
progress), January 2008. progress), January 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-MIMEtransport",
RFC 1652, July 1994. 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
skipping to change at page 18, line 43 skipping to change at page 20, line 16
for Delivery Status Notifications", RFC 3464, 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 (IDNA)",
RFC 3490, March 2003. 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", RFC 3629, November 2003.
[RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail", [RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail",
RFC 4409, April 2006. RFC 4409, April 2006.
[RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[SMTP-codes] [SMTP-codes]
Hansen , T. and J. KLensin, "A Registry for SMTP Enhanced Hansen , T. and J. Klensin, "A Registry for SMTP Enhanced
Mail System Status Codes", Mail System Status Codes",
draft-hansen-4468upd-mailesc-registry-03 (work in draft-hansen-4468upd-mailesc-registry-03 (work in
progress), January 2008. progress), January 2008.
7.2. Informative References 8.2. Informative References
[EAI-downgrading] [EAI-downgrading]
YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading
mechanism for Internationalized eMail Address", mechanism for Internationalized eMail Address",
draft-ietf-eai-downgrade-06 (work in progress), 1 2008. draft-ietf-eai-downgrade-06 (work in progress), 1 2008.
[Klensin-emailaddr] [Klensin-emailaddr]
Klensin, J., "Internationalization of Email Addresses", Klensin, J., "Internationalization of Email Addresses",
draft-klensin-emailaddr-i18n-03 (work in progress), draft-klensin-emailaddr-i18n-03 (work in progress),
July 2005. July 2005.
[RFC0974] Partridge, C., "Mail routing and the domain system",
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.
[RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission [RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission
of Large and Binary MIME Messages", RFC 3030, of Large and Binary MIME Messages", RFC 3030,
December 2000. December 2000.
[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over [RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over
Transport Layer Security", RFC 3207, February 2002. Transport Layer Security", RFC 3207, February 2002.
[RFC4954] Siemborski, R. and A. Melnikov, "SMTP Service Extension [RFC4954] Siemborski, R. and A. Melnikov, "SMTP Service Extension
for Authentication", RFC 4954, July 2007. 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 [EAI-framework], was completed extensions for internationalized email [RFC4952], was completed
before this specification, which specifies a particular part of the before this specification, which specifies a particular part of the
protocol set. This appendix, which is normative, contains material protocol set. This appendix, which is normative, contains material
that would have been incorporated into RFC 4952 had it been delayed that would have been incorporated into RFC 4952 had it been delayed
until the work described in the rest of this specification was until the work described in the rest of this specification was
completed and that should be included in any update to RFC 4952. completed and that 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 UTF8header specification
[EAI-utf8header], and strictly conformant to RFC 2822 [RFC2822]. [EAI-utf8header], and which is strictly conformant to RFC 2822
[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 UTF8header
specification [EAI-utf8header], so that it is no longer conformant specification [EAI-utf8header], 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 need 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 The existing draft standard Delivery status notifications (DSNs)
(DSNs)[RFC3461] is limited to ASCII text in the machine readable [RFC3461] is limited to ASCII text in the machine readable portions
portions of the protocol. "International Delivery and Disposition of the protocol. "International Delivery and Disposition
Notifications" [EAI-dsn] adds a new address type for international Notifications" [EAI-dsn] adds a new address type for international
email addresses so an original recipient address with non-ASCII email addresses so an original recipient address with non-ASCII
characters can be correctly preserved even after downgrading. If an characters can be correctly preserved even after downgrading. If an
SMTP server advertises both the UTF8SMTP and the DSN extension, that SMTP server advertises both the UTF8SMTP and the DSN extension, that
server MUST implement EAI-dsn [EAI-dsn] including support for the server MUST implement EAI-dsn [EAI-dsn] including support for the
ORCPT parameter. 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
skipping to change at page 20, line 51 skipping to change at page 22, line 32
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 RFC 974 sequencing rules mean when consider the question of what the [RFC0974] sequencing rules mean
different possible servers support different sets of ESMTP options when different possible servers support different sets of ESMTP
(or, in this case, addresses). The answer to this question may also options (or, in this case, addresses). The answer to this question
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
skipping to change at page 22, line 44 skipping to change at line 1052
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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