draft-ietf-eai-rfc5336bis-04.txt   draft-ietf-eai-rfc5336bis-05.txt 
Network Working Group Jiankang. Yao Network Working Group J. Yao
Internet-Draft Wei. Mao Internet-Draft W. Mao
Obsoletes: RFC5336 CNNIC Obsoletes: RFC5336 CNNIC
(if approved) October 21, 2010 (if approved) December 2, 2010
Updates: RFC5321 and 5322 Updates: RFC5321 and 5322
(if approved) (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: April 24, 2011 Expires: June 5, 2011
SMTP Extension for Internationalized Email Address SMTP Extension for Internationalized Email Address
draft-ietf-eai-rfc5336bis-04.txt draft-ietf-eai-rfc5336bis-05.txt
Abstract Abstract
This document specifies an SMTP extension for transport and delivery This document specifies an SMTP extension for transport and delivery
of email messages with internationalized email addresses or header of email messages with internationalized email addresses or header
information. This document updates some syntaxes and rules defined information. This document updates some syntax rules defined in RFC
in RFC 5321 and RFC 5322. 5321 and RFC 5322.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 24, 2011. This Internet-Draft will expire on June 5, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Role of This Specification . . . . . . . . . . . . . . . . 3 1.1. Role of This Specification . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 4 2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 5
3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 4 3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 5
3.1. Framework for the Internationalization Extension . . . . . 4 3.1. Framework for the Internationalization Extension . . . . . 5
3.2. The UTF8SMTPbis Extension . . . . . . . . . . . . . . . . 5 3.2. The UTF8SMTPbis Extension . . . . . . . . . . . . . . . . 5
3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 6 3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7
3.4. UTF8 addresses and Response Codes . . . . . . . . . . . . 7 3.4. UTF8 addresses and Response Codes . . . . . . . . . . . . 9
3.5. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 7 3.5. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 9
3.6. Additional ESMTP Changes and Clarifications . . . . . . . 8 3.6. Additional ESMTP Changes and Clarifications . . . . . . . 10
3.6.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 8 3.6.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 10
3.6.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 8 3.6.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 10
3.6.3. Trace Information . . . . . . . . . . . . . . . . . . 9 3.6.3. Trace Information . . . . . . . . . . . . . . . . . . 11
3.6.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 10 3.6.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 14 7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. draft-yao-eai-rfc5336bis: Version 00 . . . . . . . . . . . 14 7.1. draft-yao-eai-rfc5336bis: Version 00 . . . . . . . . . . . 16
7.2. draft-ietf-eai-rfc5336bis: Version 00 . . . . . . . . . . 14 7.2. draft-ietf-eai-rfc5336bis: Version 00 . . . . . . . . . . 16
7.3. draft-ietf-eai-rfc5336bis: Version 01 . . . . . . . . . . 14 7.3. draft-ietf-eai-rfc5336bis: Version 01 . . . . . . . . . . 16
7.4. draft-ietf-eai-rfc5336bis: Version 02 . . . . . . . . . . 14 7.4. draft-ietf-eai-rfc5336bis: Version 02 . . . . . . . . . . 16
7.5. draft-ietf-eai-rfc5336bis: Version 03 . . . . . . . . . . 14 7.5. draft-ietf-eai-rfc5336bis: Version 03 . . . . . . . . . . 16
7.6. draft-ietf-eai-rfc5336bis: Version 04 . . . . . . . . . . 14 7.6. draft-ietf-eai-rfc5336bis: Version 04 . . . . . . . . . . 16
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.7. draft-ietf-eai-rfc5336bis: Version 05 . . . . . . . . . . 16
8.1. Normative References . . . . . . . . . . . . . . . . . . . 14 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.2. Informative References . . . . . . . . . . . . . . . . . . 16 8.1. Normative References . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 8.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
An internationalized email address includes two parts, the local part The Simple Mail Transfer Protocol [RFC5321] provides a negotiation
and the domain part. The ways email addresses are used by protocols mechanism about service extension with which clients can discover
are different from the ways domain names are used. The most critical server capabilities and make decisions for further processing. This
difference is that emails are delivered through a chain of clients document use this mechanism to support an internationalized email
and servers, while domain names are resolved by name servers looking address. An extended overview of the extension model for
up those names in their own tables. The Simple Mail Transfer internationalized addresses and headers appears in [RFC4952bis],
Protocol [RFC5321] provides a negotiation mechanism about service referred to as "the framework document" or just as "framework"
extension with which clients can discover server capabilities and elsewhere in this specification. This document specifies an SMTP
make decisions for further processing. An extended overview of the extension to permit internationalized email addresses in envelopes,
extension model for internationalized addresses and headers appears and UNICODE characters (encoded in UTF-8) [RFC3629] in headers.
in [RFC4952bis], referred to as "the framework document" or just as
"framework" elsewhere in this specification. This document specifies
an SMTP extension to permit internationalized email addresses in
envelopes, and UNICODE characters (encoded in 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 the electronic mail. A components of, full internationalization of the 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 [RFC5321] [RFC5322] is necessary base Internet email specifications [RFC5321] [RFC5322] 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 [RFC5321] for work, specifically the definition of an SMTP extension for
internationalized email address transport delivery. internationalized email address transport delivery.
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
The terms "UTF-8 string" or "UTF-8 character" are used informally to The terms "UTF-8 string" or "UTF-8 character" are used informally to
refer to Unicode characters encoded in UTF-8 [RFC3629]. All other refer to Unicode characters encoded in UTF-8. All other specialized
specialized terms used in this specification are defined in the terms used in this specification are defined in the framework
framework document [RFC4952bis]or in the base Internet email document or in the base Internet email specifications. In
specifications [RFC5321] [RFC5322]. In particular, the terms "ASCII particular, the terms "ASCII address", "internationalized email
address", "internationalized email address", "non-ASCII address", address", "non-ASCII address", "i18mail address",
"i18mail address", "UTF8SMTPbis","conventional message", "UTF8SMTPbis","conventional message", "internationalized message",
"internationalized message", "message", and "mailing list" are used "message", and "mailing list" are used in this document according to
in this document according to the definitions in the framework the definitions in the framework document.
document [RFC4952bis].
This specification defines only those Augmented BNF (ABNF) [RFC5234] This specification defines only those Augmented BNF (ABNF) [RFC5234]
syntax rules that are different from those of the base email syntax rules that are different from those of the base email
specifications [RFC5321][RFC5322] and, where the earlier rules are specifications and, where the earlier rules are upgraded or extended,
upgraded or extended, gives them new names. When the new rule is a gives them new names. When the new rule is a small modification to
small modification to the older one, it is typically given a name the older one, it is typically given a name starting with "u". Rules
starting with "u". Rules that are undefined here may be found in the that are undefined here may be found in the base email specifications
base email specifications under the same names. 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 characters. The extension is identified with the token
token "UTF8SMTPbis". In order to provide information that may be "UTF8SMTPbis".
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 UTF-8 header specification [RFC5335bis] provides the details The EAI UTF-8 header specification [RFC5335bis] provides the details
of how and where non-ASCII characters are permitted in the header of how and where non-ASCII characters are permitted in the header
fields of messages. The context for this specification is described fields of messages. The context for this specification is described
in the framework document. in the 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
"UTF8SMTPbis". "UTF8SMTPbis".
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 reject 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
UTF8SMTPbis in its EHLO response, it MUST be fully compliant with UTF8SMTPbis in its EHLO response, it MUST be fully compliant with
this version of this specification. this version of this specification.
4. One optional parameter "UTF8REPLY" is added to the VRFY and EXPN 4. 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.
5. No additional SMTP verbs are defined by this extension. 5. No additional SMTP verbs are defined by this extension.
6. Servers offering this extension MUST provide support for, and 6. Servers offering this extension MUST provide support for, and
announce, the 8BITMIME extension [RFC1652]. announce, the 8BITMIME extension [RFC1652].
7. The reverse-path and forward-path of the SMTP MAIL and RCPT 7. 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).
8. The mail message body is extended as specified in [RFC5335bis]. 8. The mail message body is extended as specified in [RFC5335bis].
9. The UTF8SMTPbis extension is valid on the submission port 9. The UTF8SMTPbis extension is valid on the submission port
[RFC4409]. [RFC4409], and can be used with LMTP [RFC2033].
3.2. The UTF8SMTPbis Extension 3.2. The UTF8SMTPbis 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 5321 accept a UTF-8 string [RFC3629] in any position in which RFC 5321
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 [RFC5321], i.e., by separating the mailbox into as specified in [RFC5321], i.e., by separating the mailbox into
source route, local part, and domain part, using only the characters source route, local part, and domain part, using only the characters
colon (U+003A), comma (U+002C), and at-sign (U+0040) as specified colon (U+003A), comma (U+002C), and at-sign (U+0040) as specified
there. Once isolated by this parsing process, the local part MUST be there. Once isolated by this parsing process, the local part MUST be
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MUST either use a Unicode aware DNS library, or transform it to MUST either use a Unicode aware DNS library, or transform it to
A-label defined in [RFC5890]. Any domain names that are to be A-label defined in [RFC5890]. Any domain names that are to be
compared to local strings SHOULD be checked for validity and then compared to local strings SHOULD be checked for validity and then
MUST be compared as specified in section 3 of [RFC5891]. MUST be compared as specified in section 3 of [RFC5891].
An SMTP client that receives the UTF8SMTPbis extension keyword in An SMTP client that receives the UTF8SMTPbis extension keyword in
response to the EHLO command MAY transmit mailbox names within SMTP response to the EHLO command MAY transmit mailbox names within SMTP
commands as internationalized strings in UTF-8 form. It MAY send a commands as internationalized strings in UTF-8 form. It MAY send a
UTF-8 header [RFC5335bis] (which may also include mailbox names in UTF-8 header [RFC5335bis] (which may also include mailbox names in
UTF-8). It MAY transmit the domain parts of mailbox names within UTF-8). It MAY transmit the domain parts of mailbox names within
SMTP commands or the message header as either ACE (ASCII Compatible SMTP commands or the message header as A-labels or U-labels
Encoding) labels (as specified in IDNA definitions [RFC5890]) or [RFC5890]. All labels in domain parts of mailbox names which are IDN
UTF-8 strings. All labels in domain parts of mailbox names which are forms of A-labels or U-labels MUST be valid. When a Mail User
IDNs (either UTF-8 or ACE strings) MUST be valid. When a Message Agent(MUA) submits a message to a Message Submission Server
User Agent submits a message to a Message Submission Server
("MSA")[RFC4409], it is the responsibility of the MSA to ensure that ("MSA")[RFC4409], it is the responsibility of the MSA to ensure that
all domain labels are valid. The presence of the UTF8SMTPbis all domain labels are valid. The presence of the UTF8SMTPbis
extension does not change the requirement of RFC 5321 that servers extension does not change the requirement of RFC 5321 that servers
relaying mail MUST NOT attempt to parse, evaluate, or transform the relaying mail MUST NOT attempt to parse, evaluate, or transform the
local part in any way. local part in any way.
If the UTF8SMTPbis SMTP extension is not offered by the server, the If the UTF8SMTPbis SMTP extension is not offered by the server, the
SMTP client MUST NOT transmit an internationalized address and MUST SMTP client MUST NOT transmit an internationalized address and MUST
NOT transmit a mail message containing internationalized mail headers NOT transmit a mail message containing internationalized mail headers
as described in [RFC5335bis] at any level within its MIME structure as described in [RFC5335bis] at any level within its MIME structure
[RFC2045] and [RFC2047]. (For this paragraph, the internationalized [RFC2045] and [RFC2047]. (For this paragraph, the internationalized
domain name in the form of ACE labels as specified in IDNA domain name in the form of A-labels as specified in IDNA definitions
definitions [RFC5890] is not considered to be "internationalized".) [RFC5890] is not considered to be "internationalized".) Instead, if
Instead, if an SMTP client (SMTP sender) attempts to transfer an an SMTP client (SMTP sender) attempts to transfer an
internationalized message and encounters a server that does not internationalized message and encounters a server that does not
support the extension, it MUST make one of the following three support the extension, it MUST make one of the following three
choices: 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 5321 [RFC5321] and RFC 5322 consistent with the provisions of RFC 5321 [RFC5321] and RFC 5322
[RFC5322]. [RFC5322].
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accept the message and then generate and transmit a notification accept the message and then generate and transmit a notification
of non-deliverability. Such notification MUST be done as of non-deliverability. Such notification MUST be done as
specified in RFC 5321 [RFC5321], RFC 3464 [RFC3464], and the EAI specified in RFC 5321 [RFC5321], RFC 3464 [RFC3464], and the EAI
delivery status notification (DSN) specification [RFC5337bis]. delivery status notification (DSN) specification [RFC5337bis].
3. It may find an alternate route to the destination that permits 3. It may find an alternate route to the destination that permits
UTF8SMTPbis. That route may be discovered by trying alternate UTF8SMTPbis. That route may be discovered by trying alternate
Mail eXchanger (MX) hosts (using preference rules as specified in Mail eXchanger (MX) hosts (using preference rules as specified in
RFC 5321) or using other means available to the SMTP-sender. RFC 5321) or using other means available to the SMTP-sender.
This document applies only when an UTF8SMTPbis-aware client is trying This document applies only when an UTF8SMTPbis-aware client is trying
to send an internationalized message to a server which requires the to send an internationalized message to an UTF8SMTPbis-aware server.
UTF8SMTPbis extensions to handle it. For all other cases, and for For all other cases, and for addresses and messages that do not
addresses and messages that do not require an UTF8SMTPbis extension, require an UTF8SMTPbis extension, SMTP clients and servers are
SMTP clients and servers are expected to behave exactly as specified expected to behave exactly as specified in [RFC5321].
in [RFC5321].
A UTF8SMTPbis aware MUA/MSA sending to a legacy SMTP server [RFC5321] A UTF8SMTPbis aware MUA/MSA sending to a legacy SMTP server [RFC5321]
and [RFC5322] MAY convert the ASCII@non-ASCII address into the format and [RFC5322] MAY convert an ASCII@non-ASCII address into the format
of ASCII@A-label [RFC5890] if the email address is in the format of of ASCII@A-label [RFC5890] if the email address is in the format of
ASCII@non-ASCII. ASCII@non-ASCII.
3.3. Extended Mailbox Address Syntax 3.3. Extended Mailbox Address Syntax
RFC 5321, Section 4.1.2, defines the syntax of a mailbox entirely in RFC 5321, 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 productions 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
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conformant with IDNA definitions [RFC5890]. conformant with IDNA definitions [RFC5890].
o Change the definition of "Local-part" to permit either the o Change the definition of "Local-part" to permit either the
definition above or a UTF-8 string. That string MUST NOT contain definition above or a UTF-8 string. That string MUST NOT contain
any of the ASCII characters (either graphics or controls) that are any of the ASCII characters (either graphics or controls) that are
not permitted in "atext"; it is otherwise unrestricted. not 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 follows. [RFC5234] as follows.
uMailbox = uLocal-part "@" uDomain uMailbox = uLocal-part "@" ( uDomain / address-literal )
; uLocal-part and uDomain defined ; Replace Mailbox in RFC 5321, Section 4.1.2
; in RFC 5335bis, Section 4.
address-literal = <See Section 4.1.2 of RFC 5321>
uLocal-part = uDot-string / uQuoted-string
; MAY be case-sensitive
; Replace Local-part in RFC 5321, Section 4.1.2
uDot-string = uAtom *("." uAtom)
; Replace Dot-string in RFC 5321, Section 4.1.2
uAtom = 1*ucharacter
; Replace Atom in RFC 5321, Section 4.1.2
ucharacter = atext / UTF8-non-ascii
atext = <See Section 3.2.3 of RFC 5322>
uQuoted-string = DQUOTE *uqcontent DQUOTE
; Replace Quoted-string in RFC 5321, Section 4.1.2
DQUOTE = <See appendix B.1 of RFC 5234>
uqcontent = qcontent / UTF8-non-ascii
qcontent = <See Section 3.2.4 of RFC 5322>
uDomain = sub-udomain *("." sub-udomain)
; Replace Domain in RFC 5321, Section 4.1.2
sub-udomain = uLet-dig [uLdh-str]
; Replace sub-domain in RFC 5321, Section 4.1.2
uLet-dig = Let-dig / UTF8-non-ascii
Let-dig = <See Section 4.1.2 of RFC 5321>
uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-non-ascii) uLet-dig
; Replace Ldh-str in RFC 5321, Section 4.1.2
UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4
UTF8-2 = <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 IDNA definitions The value of "uDomain" SHOULD be verified by IDNA definitions
[RFC5890]. If that verification fails, the email address with that [RFC5890]. If that verification fails, the email address with that
uDomain MUST NOT be regarded as a valid email address. uDomain MUST NOT be regarded as a valid email address.
3.4. UTF8 addresses and Response Codes 3.4. UTF8 addresses and Response Codes
An "internationalized message" as defined in the appendix of this An internationalized message MUST NOT be sent to an SMTP server that
specification MUST NOT be sent to an SMTP server that does not does not support UTF8SMTPbis. Such a message should be rejected by a
support UTF8SMTPbis. Such a message should be rejected by a server server if it lacks the support of UTF8SMTPbis.
if it lacks the support of UTF8SMTPbis.
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 5321. their meanings as defined in RFC 5321.
When messages are rejected because the RCPT command requires an ASCII When messages are rejected because the RCPT command requires an ASCII
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 ASCII address, the response code 550 is the MAIL command requiring an ASCII 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
"X.6.7" [RFC5248] is used, meaning that "UTF-8 addresses not "X.6.7" [RFC5248] is used, meaning that "UTF-8 addresses not
permitted for that sender/recipient". permitted for that sender/recipient".
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 "X.6.9" [RFC5248] is used, status codes [RFC3463], response code "X.6.9" [RFC5248] is used,
meaning that "UTF-8 header message can not be transferred to one or meaning that "UTF-8 header message can not be transferred to one or
more recipient so the message must be bounced". more recipient so the message must be rejected".
3.5. Body Parts and SMTP Extensions 3.5. 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 [RFC2045] and parse all message header fields and MIME header fields [RFC2045] and
[RFC2047] in the message body. [RFC2047] in the message body.
While this specification requires that servers support the 8BITMIME While this specification requires that servers support the 8BITMIME
skipping to change at page 8, line 33 skipping to change at page 10, line 21
without restriction as to line lengths or delimiters. without restriction as to line lengths or delimiters.
3.6. Additional ESMTP Changes and Clarifications 3.6. 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 5321 specifies a them. In general, the rule is that, when RFC 5321 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 5321 specifies a domain name, the name SHOULD be in string; when RFC 5321 specifies a domain name, the name SHOULD be in
the form of ACE labels if its raw form is non-ASCII. the form of A-label 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.
3.6.1. The Initial SMTP Exchange 3.6.1. 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 response 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 UTF8SMTPbis until client cannot know whether the server supports UTF8SMTPbis until
after it receives the response from EHLO, any domain names that after it receives the response from EHLO, the client must send only
appear in this dialogue, or in responses to EHLO, MUST be in the ASCII (LDH label [RFC5890] or A-label) domains in the EHLO command
hostname form, i.e., internationalized ones MUST be in the form of and that, if the server provides domain names in the EHLO response,
ACE labels. they must be in the form of LDH labels or A-labels.
3.6.2. Mail eXchangers 3.6.2. 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 RFC 5321. When are generally listed in MX records as described in RFC 5321. 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
UTF8SMTPbis extension. Otherwise, surprising downgrades can happen UTF8SMTPbis extension. Otherwise, surprising rejections can happen
during temporary failures, which users might perceive as a serious during temporary failures, which users might perceive as a serious
reliability issue. reliability issue. In order to avoid the possible surprising
rejections, you may also implement the advice in EAI addresses advice
document [EAI addresses] and EAI deployment advice document [EAI
Deployment].
3.6.3. Trace Information 3.6.3. 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, RFC 5321 requires that it MUST insert trace ("time stamp"
information at the beginning of the message content. "Time stamp" or or "Received") information at the beginning of the message content.
"Received" appears in the form of "Received:" lines. The most For the trace information, this memo updates the time stamp line and
important use of Received: lines is for debugging mail faults. When the return path line [RFC5321] formally defined as follows:
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
primary purpose of the Return-path is to designate the address to
which messages indicating non-delivery or other mail system failures
are to be sent. For the trace information, this memo updates the
time stamp line and the return path line [RFC5321] formally defined
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 RFC 5321 ; Replaces Return-path-line in Section 4.4 of RFC 5321
; uReverse-path is defined in Section 4 of RFC5335bis
uReverse-path = uPath / "<>"
; Replace Reverse-path in RFC 5321, section 4.1.2
uPath = "<" [ A-d-l ":" ] uMailbox ">"
; Replace Path in RFC 5321, section 4.1.2
; uMailbox is defined in section 3.3 of this document
A-d-l = <See section 4.1.2 of RFC 5321>
uTime-stamp-line = "Received:" FWS uStamp <CRLF> uTime-stamp-line = "Received:" FWS uStamp <CRLF>
; Replaces Time-stamp-line in Section 4.4 of RFC 5321 ; Replaces Time-stamp-line in Section 4.4 of RFC 5321
uStamp = From-domain By-domain uOpt-info ";" FWS date-time uStamp = From-domain By-domain uOpt-info [CFWS] ";" FWS date-time
; Replaces Stamp in Section 4.4 of RFC 5321 ; Replaces Stamp in Section 4.4 of RFC 5321
From-domain = <See section 4.4 of RFC 5321>
By-domain = <See section 4.4 of RFC 5321>
date-time = <See section 3.3 of RFC 5322>
uOpt-info = [Via] [With] [ID] [uFor] uOpt-info = [Via] [With] [ID] [uFor]
[Additional-Registered-Clauses]
; Replaces Opt-info in Section 4.4 of RFC 5321 ; Replaces Opt-info in Section 4.4 of RFC 5321
; The protocol value for With will allow a UTF8SMTPbis value ; The protocol value for With will allow a UTF8SMTPbis value
uFor = "FOR" ( FWS (uPath / uMailbox) ) CFWS Via = <See section 4.4 of RFC 5321>
With = <See section 4.4 of RFC 5321>
ID = <See section 4.4 of RFC 5321>
Additional-Registered-Clauses = <See section 4.4 of RFC 5321>
uFor = CFWS "FOR" FWS ( uPath / uMailbox)
; Replaces For in Section 4.4 of RFC 5321 ; Replaces For in Section 4.4 of RFC 5321
; uMailbox is defined in section 3.3 of this document ; uMailbox is defined in section 3.3 of this document
uPath = "<" [ A-d-l ":" ] uMailbox ">"
; Replace Path in RFC 5321, section 4.1.2
; A-d-l is defined in RFC 5321, section 4.1.2
; uMailbox is defined in section 3.3 of this document
Except in the 'uFor' clause and 'uReverse-path' value where non-ASCII Except in the 'uFor' clause and 'uReverse-path' value where non-ASCII
domain names may be used, internationalized domain names in Received domain names may be used, internationalized domain names in Received
fields MUST be transmitted in the form of ACE labels. The protocol fields MUST be transmitted in the form of A-labels. The protocol
value of the WITH clause when this extension is used is one of the value of the WITH clause when this extension is used is one of the
UTF8SMTPbis values specified in the "IANA Considerations" section of UTF8SMTPbis values specified in the "IANA Considerations" section of
this document. this document.
3.6.4. UTF-8 Strings in Replies 3.6.4. UTF-8 Strings in Replies
3.6.4.1. MAIL and RCPT Commands 3.6.4.1. RCPT Commands
If the client issues a RCPT command containing non-ASCII characters,
the SMTP server is permitted to use UTF-8 characters in the email
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, the SMTP server is permitted
and process 251 or 551 responses containing UTF-8 email addresses. to use UTF-8 characters in the email address associated with 251 and
If a given RCPT command does not include a non-ASCII envelope 551 response codes, and the client MUST be able to accept and process
them. If a given RCPT command does not include a non-ASCII envelope
address, the server MUST NOT return a 251 or 551 response containing address, the server MUST NOT return a 251 or 551 response containing
a non-ASCII mailbox. Instead, it MUST transform such responses into a non-ASCII mailbox. Instead, it MUST transform such responses into
250 or 550 responses that do not contain addresses. 250 or 550 responses that do not contain non-ASCII addresses.
3.6.4.2. VRFY and EXPN Commands and the UTF8REPLY Parameter 3.6.4.2. 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 the optional
parameter "UTF8REPLY", it indicates the client can accept UTF-8 parameter "UTF8REPLY", it indicates the client can accept UTF-8
strings in replies to those commands. This allows the server to use strings in replies to those commands. This allows the server to use
UTF-8 strings in mailbox names and full names that occur in replies UTF-8 strings in mailbox names and full names that occur in replies
without concern that the client might be confused by them. An SMTP without concern that the client might be confused by them. An SMTP
client that conforms to this specification MUST accept and correctly client that conforms to this specification MUST accept and correctly
process replies from the VRFY and EXPN commands that contain UTF-8 process replies from the VRFY and EXPN commands that contain UTF-8
strings. However, the SMTP server MUST NOT use UTF-8 strings in strings. However, the SMTP server MUST NOT use UTF-8 strings in
replies if the SMTP client does not specifically allow such replies replies if the SMTP client does not specifically allow such replies
by transmitting this parameter. Most replies do not require that a by transmitting this parameter. Most replies do not require that a
mailbox name be included in the returned text, and therefore UTF-8 is mailbox name be included in the returned text, and therefore UTF-8 is
not needed in them. Some replies, notably those resulting from not needed in them. Some replies, notably those resulting from
successful execution of the VRFY and EXPN commands, do include the successful execution of the VRFY and EXPN commands, do include the
mailbox, making the provisions of this section important. 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 = "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 = "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 did not use the "UTF8REPLY" parameter, then the server MUST client did not use the "UTF8REPLY" parameter, then the server MUST
use either the response code 252 or 550. Response code 252, defined use either the response code 252 or 550. Response code 252, defined
in [RFC5321], means "Cannot VRFY user, but will accept the message in [RFC5321], means "Cannot VRFY user, but will accept the message
and attempt the delivery". Response code 550, also defined in and attempt the delivery". Response code 550, also defined in
[RFC5321], means "Requested action not taken: mailbox unavailable". [RFC5321], means "Requested action not taken: mailbox unavailable".
skipping to change at page 11, line 28 skipping to change at page 13, line 30
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 "X.6.8" or "X.6.10" [RFC3463], the enhanced response code [RFC5248] is either "X.6.8" if
[RFC5248], meaning "A reply containing a UTF-8 string is required to the associated basic status code [RFC5321] is 252 or "Y.6.8" if the
show the mailbox name, but that form of response is not permitted by associated basic status code [RFC5321] is 553 or 550, meaning "A
the client". reply containing a UTF-8 string is required to show the mailbox name,
but that form of response is not permitted by the client".
If the SMTP client does not support the UTF8SMTPbis extension, but If the SMTP client does not support the UTF8SMTPbis extension, but
receives a UTF-8 string in a reply, it may not be able to properly receives a UTF-8 string in a reply, it may not be able to properly
report the reply to the user, and some clients might 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
skipping to change at page 12, line 18 skipping to change at page 14, line 20
| UTF8SMTPbis | Internationalized email address | [RFCXXXX] | | UTF8SMTPbis | Internationalized email address | [RFCXXXX] |
+-------------+---------------------------------+-----------+ +-------------+---------------------------------+-----------+
This document updates the values to the SMTP Enhanced Status Code This document updates the 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 Sections 3.4 and 3.6.4.2 of this document, and being based on in Sections 3.4 and 3.6.4.2 of this document, and being based on
[RFC5248]. The registration data is as follows: [RFC5248]. The registration data is as follows:
Code: X.6.7 Code: X.6.7
Sample Text: UTF-8 addresses not permitted Sample Text: UTF-8 addresses not permitted
for that sender/recipient for that sender/recipient
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
command that rUTF-8 addresses are not permitted command that rUTF-8 addresses are not permitted
Defined: RFC XXXX (Standard track) Defined: RFC XXXX (Standard track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: ima@ietf.org
Code: X.6.8 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 (Standard track) Defined: RFC XXXX (Standard track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: ima@ietf.org
Code: X.6.9 Code: X.6.9
Sample Text: UTF-8 header message can not be transferred Sample Text: UTF-8 header message can not be transferred
to one or more recipient so the message to one or more recipient so the message
must be bounced must be rejected
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 (Standard track) Defined: RFC XXXX (Standard track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: ima@ietf.org
Code: X.6.10 Code: Y.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: 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 (Standard track) Defined: RFC XXXX (Standard track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: IESG. Change controller: ima@ietf.org
The "Mail Transmission Types" registry under the Mail Parameters The "Mail Transmission Types" registry under the Mail Parameters
registry is requested to be updated to include the following new registry is requested to be updated to include the following new
entries: entries:
+---------------+-----------------------------+---------------------+ +---------------+-----------------------------+---------------------+
| WITH protocol | Description | Reference | | WITH protocol | Description | Reference |
| types | | | | types | | |
+---------------+-----------------------------+---------------------+ +---------------+-----------------------------+---------------------+
| UTF8SMTPbis | UTF8SMTPbis with Service | [RFCXXXX] | | UTF8SMTPbis | UTF8SMTPbis with Service | [RFCXXXX] |
skipping to change at page 14, line 43 skipping to change at page 16, line 43
7.5. draft-ietf-eai-rfc5336bis: Version 03 7.5. draft-ietf-eai-rfc5336bis: Version 03
improve the text improve the text
7.6. draft-ietf-eai-rfc5336bis: Version 04 7.6. draft-ietf-eai-rfc5336bis: Version 04
update the abstract update the abstract
improve the text improve the text
8. References 7.7. draft-ietf-eai-rfc5336bis: Version 05
improve the text based on AD and Co-chairs
8. References
8.1. Normative References 8.1. Normative References
[ASCII] American National Standards Institute (formerly United [ASCII] American National Standards Institute (formerly United
States of America Standards Institute), "USA Code for States of America Standards Institute), "USA Code for
Information Interchange", ANSI X3.4-1968, 1968. Information Interchange", ANSI X3.4-1968, 1968.
[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.
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033,
October 1996.
[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.
[RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service
Extension for Delivery Status Notifications (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 Format
for Delivery Status Notifications", RFC 3464, for Delivery Status Notifications", RFC 3464,
January 2003. January 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.
skipping to change at page 15, line 46 skipping to change at page 17, line 50
[RFC5248] Hansen , T. and J. Klensin, "A Registry for SMTP Enhanced [RFC5248] Hansen , T. and J. Klensin, "A Registry for SMTP Enhanced
Mail System Status Codes", RFC 5248, June 2008. Mail System Status Codes", RFC 5248, June 2008.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008. October 2008.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008. October 2008.
[RFC5335bis] [RFC5335bis]
Abel, Y., Ed., "Internationalized Email Headers", Abel, Y. and S. Steel, "Internationalized Email Headers",
RFC 5335, August 2010. RFC 5335, December 2010.
[RFC5337bis] [RFC5337bis]
Newman, C. and A. Melnikov, Ed., "Internationalized Newman, C. and A. Melnikov, Ed., "Internationalized
Delivery Status and Disposition Notifications", RFC 5337, Delivery Status and Disposition Notifications", RFC 5337,
August 2008. August 2008.
[RFC5890] Klensin, J., "Internationalizing Domain Names in [RFC5890] Klensin, J., "Internationalizing Domain Names in
Applications (IDNA definitions)", RFC 5890, June 2010. Applications (IDNA definitions)", RFC 5890, June 2010.
[RFC5891] Klensin, J., "Internationalized Domain Names in [RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891, August 2010. Applications (IDNA): Protocol", RFC 5891, August 2010.
8.2. Informative References 8.2. Informative References
[RFC0974] Partridge, C., "Mail routing and the domain system", [EAI Deployment]
RFC 974, January 1986. Yao, J., Lee, X., and S. Steel, "Advice for EAI
deployment", draft 5335, December 2010.
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033, [EAI addresses]
October 1996. Steel, S., Yao, J., and Mark. Davis, "Advice for non-ASCII
& ASCII addresses", draft 5335, December 2010.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996. Bodies", RFC 2045, November 1996.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text", Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996. RFC 2047, November 1996.
[RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission [RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission
 End of changes. 55 change blocks. 
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