draft-ietf-eai-rfc5336bis-07.txt   draft-ietf-eai-rfc5336bis-08.txt 
Network Working Group J. Yao Network Working Group J. Yao
Internet-Draft W. Mao Internet-Draft W. Mao
Obsoletes: RFC5336 CNNIC Obsoletes: RFC5336 CNNIC
(if approved) December 4, 2010 (if approved) March 7, 2011
Updates: RFC5321 and 5322 Updates: RFC5321 and 5322
(if approved) (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: June 7, 2011 Expires: September 8, 2011
SMTP Extension for Internationalized Email Address SMTP Extension for Internationalized Email Address
draft-ietf-eai-rfc5336bis-07.txt draft-ietf-eai-rfc5336bis-08.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 syntax rules defined in RFC information.
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 June 7, 2011. This Internet-Draft will expire on September 8, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Role of This Specification . . . . . . . . . . . . . . . . 4 1.1. Role of This Specification . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Updates to Other Specifications . . . . . . . . . . . . . 5
2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 5 2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 5
3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 5 3. Mail Transport-Level Protocol . . . . . . . . . . . . . . . . 5
3.1. Framework for the Internationalization Extension . . . . . 5 3.1. Framework for the Internationalization Extension . . . . . 5
3.2. The UTF8SMTPbis Extension . . . . . . . . . . . . . . . . 5 3.2. The UTF8SMTPbis Extension . . . . . . . . . . . . . . . . 6
3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7 3.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 7
3.4. UTF8 addresses and Response Codes . . . . . . . . . . . . 9 3.4. MAIL Command Parameter Usage . . . . . . . . . . . . . . . 10
3.5. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 9 3.5. Non-ASCII addresses and Reply-codes . . . . . . . . . . . 10
3.6. Additional ESMTP Changes and Clarifications . . . . . . . 10 3.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 11
3.6.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 10 3.7. Additional ESMTP Changes and Clarifications . . . . . . . 11
3.6.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 10 3.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 11
3.6.3. Trace Information . . . . . . . . . . . . . . . . . . 11 3.7.2. Mail eXchangers . . . . . . . . . . . . . . . . . . . 12
3.6.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 12 3.7.3. Trace Information . . . . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 3.7.4. UTF-8 Strings in Replies . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. draft-yao-eai-rfc5336bis: Version 00 . . . . . . . . . . . 16 7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 18
7.2. draft-ietf-eai-rfc5336bis: Version 00 . . . . . . . . . . 16 7.1. draft-yao-eai-rfc5336bis: Version 00 . . . . . . . . . . . 18
7.3. draft-ietf-eai-rfc5336bis: Version 01 . . . . . . . . . . 16 7.2. draft-ietf-eai-rfc5336bis: Version 00 . . . . . . . . . . 19
7.4. draft-ietf-eai-rfc5336bis: Version 02 . . . . . . . . . . 16 7.3. draft-ietf-eai-rfc5336bis: Version 01 . . . . . . . . . . 19
7.5. draft-ietf-eai-rfc5336bis: Version 03 . . . . . . . . . . 16 7.4. draft-ietf-eai-rfc5336bis: Version 02 . . . . . . . . . . 19
7.6. draft-ietf-eai-rfc5336bis: Version 04 . . . . . . . . . . 16 7.5. draft-ietf-eai-rfc5336bis: Version 03 . . . . . . . . . . 19
7.7. draft-ietf-eai-rfc5336bis: Version 05 . . . . . . . . . . 16 7.6. draft-ietf-eai-rfc5336bis: Version 04 . . . . . . . . . . 19
7.8. draft-ietf-eai-rfc5336bis: Version 06 . . . . . . . . . . 17 7.7. draft-ietf-eai-rfc5336bis: Version 05 . . . . . . . . . . 19
7.9. draft-ietf-eai-rfc5336bis: Version 07 . . . . . . . . . . 17 7.8. draft-ietf-eai-rfc5336bis: Version 06 . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.9. draft-ietf-eai-rfc5336bis: Version 07 . . . . . . . . . . 19
8.1. Normative References . . . . . . . . . . . . . . . . . . . 17 7.10. draft-ietf-eai-rfc5336bis: Version 08 . . . . . . . . . . 19
8.2. Informative References . . . . . . . . . . . . . . . . . . 18 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 8.1. Normative References . . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
The Simple Mail Transfer Protocol [RFC5321] provides a negotiation The Simple Mail Transfer Protocol [RFC5321] provides a negotiation
mechanism about service extension with which clients can discover mechanism about service extension by which SMTP clients can discover
server capabilities and make decisions for further processing. This SMTP server capabilities and make decisions for further processing.
document use this mechanism to support an internationalized email This document uses this mechanism and specifies an SMTP extension to
address. An extended overview of the extension model for permit internationalized email addresses (see Section 1.2) in the
internationalized addresses and headers appears in [RFC4952bis], SMTP envelope, and Unicode characters encoded in UTF-8 [RFC3629] in
referred to as "the framework document" or just as "framework" the headers. An extended overview of the extension model for
elsewhere in this specification. This document specifies an SMTP internationalized email addresses and the email header appears in
extension to permit internationalized email addresses in envelopes, [RFC4952bis], referred to as "the framework document" or just as
and UNICODE characters (encoded in UTF-8) [RFC3629] in headers. "framework" elsewhere in this specification.
[[anchor1: Note in Draft and to RFC Editor: The keyword represented
in this document by "UTF8SMTPbis" (and in the XML source
byUTF8SMTPbis) is a placeholder. The actual keyword will be assigned
when the standards track SMTP extension in this series [RFC5336bis-
SMTP] is approved for publication and should be substituted here.
This paragraph should be treated as normative reference to that SMTP
extension draft, creating a reference hold until it is approved by
the IESG. This paragraph should be removed before RFC publication.]]
1.1. Role of This Specification 1.1. Role of This Specification
The framework document specifies the requirements for, and describes The framework document [RFC4952bis] specifies the requirements for,
components of, full internationalization of the electronic mail. A and describes components of, full internationalization of electronic
thorough understanding of the information in that document and in the mail. A thorough understanding of the information in that document
base Internet email specifications [RFC5321] [RFC5322] is necessary and in the base Internet email specifications [RFC5321] [RFC5322] is
to understand and implement this specification. necessary 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 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", "MAY", and "OPTIONAL" in this document are to
document are to be interpreted as described in RFC 2119 [RFC2119]. 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 to refer to
refer to Unicode characters encoded in UTF-8. All other specialized Unicode characters encoded in UTF-8. All other specialized terms
terms used in this specification are defined in the framework used in this specification are defined in the framework document or
document or in the base Internet email specifications. In in the base Internet email specifications. In particular, the terms
particular, the terms "ASCII address", "internationalized email "ASCII address", "internationalized email address", "non-ASCII
address", "non-ASCII address", "i18mail address", address", "UTF8SMTPbis", "internationalized message", and "message"
"UTF8SMTPbis","conventional message", "internationalized message", are used in this document according to the definitions in the
"message", and "mailing list" are used in this document according to framework document.
the definitions in the framework document.
This specification defines only those Augmented BNF (ABNF) [RFC5234] Non-ASCII characters or strings referred in this document MUST be
syntax rules that are different from those of the base email expressed in UTF-8, a standard Unicode Encoding Form.
specifications and, where the earlier rules are upgraded or extended,
gives them new names. When the new rule is a small modification to This specification uses Augmented BNF (ABNF) rules [RFC5234], with
the older one, it is typically given a name starting with "u". Rules some modifications. The modified rules are defined in this
that are undefined here may be found in the base email specifications specification. When a new rule has a name starting with "u", it is a
under the same names. small modification to an older rule. Rules that are undefined here
can be found from [RFC5234] or [RFC5321] or [RFC5322] under the same
names.
1.3. Updates to Other Specifications
This specification modifies RFC 5321 by permitting internationalized
email address in the envelop. It also updates some syntax rules
defined in RFC 5321. It modifies RFC 5322 by permitting data formats
defined in [RFC5335bis]. It does not modify the 8BITMIME
specification [RFC6152] in any way, but it does require that the
8BITMIME extension be announced by the EAI-aware SMTP server and used
with "BODY=8BMITMIME".
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 characters in both the
the envelope and header fields of messages, which are encoded with envelope and header fields of messages, which are encoded in UTF-8.
UTF-8 characters. The extension is identified with the token The extension is identified with the token "UTF8SMTPbis".
"UTF8SMTPbis".
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 email header features enabled by this extension
fields of messages. The context for this specification is described
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 this keyword.
Clients MUST reject any parameters; that is, clients MUST behave The EAI-aware SMTP client MUST reject any parameters if they
as if the parameters do not appear. If a server includes appear for this keyword; that is, the EAI-aware SMTP client MUST
UTF8SMTPbis in its EHLO response, it MUST be fully compliant with behave as if the parameters do not appear. If an SMTP server
this version of this specification. includes UTF8SMTPbis in its EHLO response, it MUST be fully
4. One optional parameter "UTF8REPLY" is added to the VRFY and EXPN compliant with this version of this specification.
commands. The parameter UTF8REPLY has no value. The parameter 4. One OPTIONAL parameter "UTF8SMTPbis" is added to the MAIL
indicates that the SMTP client can accept Unicode characters in command. The parameter has no value. If this parameter is set
UTF-8 encoding in replies from the VRFY and EXPN commands. in the MAIL command, it indicates that the SMTP client is EAI-
5. No additional SMTP verbs are defined by this extension. aware and asserts that the envelop includes the non-ASCII
6. Servers offering this extension MUST provide support for, and address or the message being sent is internationalized message
announce, the 8BITMIME extension [RFC1652]. or the message being sent needs the UTF8SMTPbis support.
7. The reverse-path and forward-path of the SMTP MAIL and RCPT 5. The maximum length of a MAIL command line is increased by 12
commands are extended to allow Unicode characters encoded in characters by the possible addition of the UTF8SMTPbis
UTF-8 in mailbox names (addresses). parameter. [[anchor6: RFC Editor: the number '12' will be
8. The mail message body is extended as specified in [RFC5335bis]. replaced by the new number (1 space + length of the new keyword
9. The UTF8SMTPbis extension is valid on the submission port supposed to replace "UTF8SMTPbis").]]
[RFC4409], and can be used with LMTP [RFC2033]. 6. One OPTIONAL parameter "UTF8SMTPbis" is added to the VRFY and
EXPN commands. The parameter UTF8SMTPbis has no value. The
parameter indicates that the SMTP client can accept Unicode
characters in UTF-8 encoding in replies from the VRFY and EXPN
commands.
7. No additional SMTP verbs are defined by this extension.
8. Servers offering this extension MUST provide support for, and
announce, the 8BITMIME extension [RFC6152].
9. The reverse-path and forward-path of the SMTP MAIL and RCPT
commands are extended to allow Unicode characters encoded in
UTF-8 in mailbox names (addresses).
10. The mail message body is extended as specified in [RFC5335bis].
11. The UTF8SMTPbis extension is valid on the submission port
[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 UTF8SMTPbis extension MUST be
accept a UTF-8 string [RFC3629] in any position in which RFC 5321 prepared to accept a UTF-8 string [RFC3629] in any position in which
specifies that a mailbox can appear. That string MUST be parsed only RFC 5321 specifies that a <mailbox> can appear. Although the
as specified in [RFC5321], i.e., by separating the mailbox into characters in the <local-part> are permitted to contain non-ASCII
source route, local part, and domain part, using only the characters characters, actual parsing of the <local-part>, and the delimiters
colon (U+003A), comma (U+002C), and at-sign (U+0040) as specified used, are unchanged from the base email specification [RFC5321]. Any
there. Once isolated by this parsing process, the local part MUST be domain names to be looked up in the DNS MUST allow for [RFC5890]
treated as opaque unless the SMTP server is the final delivery Mail behavior. When doing lookups, the EAI-aware SMTP server MUST either
Transfer Agent (MTA). Any domain names to be looked up in the DNS use a Unicode aware DNS library, or transform it to A-label defined
MUST allow for [RFC5890] behavior. When doing lookups, the server in [RFC5890].
MUST either use a Unicode aware DNS library, or transform it to
A-label defined in [RFC5890]. Any domain names that are to be
compared to local strings SHOULD be checked for validity and then
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 A-labels or U-labels SMTP commands or the message header as A-labels or U-labels
[RFC5890]. All labels in domain parts of mailbox names which are IDN [RFC5890]. The presence of the UTF8SMTPbis extension does not change
forms of A-labels or U-labels MUST be valid. When a Mail User RFC 5321 server relaying behaviors.
Agent(MUA) submits a message to a Message Submission Server
("MSA")[RFC4409], it is the responsibility of the MSA to ensure that
all domain labels are valid. The presence of the UTF8SMTPbis
extension does not change the requirement of RFC 5321 that servers
relaying mail MUST NOT attempt to parse, evaluate, or transform the
local part in any way.
If the UTF8SMTPbis SMTP extension is not offered by the server, the
SMTP client MUST NOT transmit an internationalized address and MUST
NOT transmit a mail message containing internationalized mail headers
as described in [RFC5335bis] at any level within its MIME structure
[RFC2045] and [RFC2047]. (For this paragraph, the internationalized
domain name in the form of A-labels as specified in IDNA definitions
[RFC5890] is not considered to be "internationalized".) Instead, if
an SMTP client (SMTP sender) attempts to transfer an
internationalized message and encounters a server that does not
support the extension, it MUST make one of the following three
choices:
1. If and only if the SMTP client (sender) is a Message Submission If the UTF8SMTPbis SMTP extension is not offered by the SMTP server,
Server ("MSA") [RFC4409], it MAY, consistent with the general the EAI-aware SMTP client MUST NOT transmit an internationalized
provisions for changes by such servers, rewrite the envelope, email address and MUST NOT transmit a mail message containing
headers, or message material to make them entirely ASCII and internationalized mail headers as described in [RFC5335bis] at any
consistent with the provisions of RFC 5321 [RFC5321] and RFC 5322 level within its MIME structure [RFC2045] and [RFC2047]. (For this
[RFC5322]. paragraph, the internationalized domain name in the form of A-labels
as specified in IDNA definitions [RFC5890] is not considered to be
"internationalized".) Instead, if an EAI-aware SMTP client (EAI-
aware SMTP sender) attempts to transfer an internationalized message
and encounters an SMTP server that does not support the extension, it
MUST make one of the following three choices and the priority order
is 1, 2 and 3.
2. It may either reject the message during the SMTP transaction or 1. It MAY either reject the message during the SMTP transaction or
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 2. If and only if the EAI-aware SMTP client (sender) is a Message
UTF8SMTPbis. That route may be discovered by trying alternate Submission Agent ("MSA") [RFC4409] [RFC5598], it MAY rewrite the
envelope, headers, or message material to make them entirely
ASCII [ASCII] and consistent with the provisions of RFC 5321
[RFC5321] and RFC 5322 [RFC5322].
3. It MAY find an alternate route to the destination that permits
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 EAI-aware SMTP
client.
This document applies only when an UTF8SMTPbis-aware client is trying This document applies only when an EAI-aware SMTP client is trying to
to send an internationalized message to an UTF8SMTPbis-aware server. send an internationalized message to an EAI-aware SMTP server. For
For all other cases, and for addresses and messages that do not all other cases, and for addresses and messages that do not require
require an UTF8SMTPbis extension, SMTP clients and servers are an UTF8SMTPbis extension, EAI-aware SMTP clients and servers do not
expected to behave exactly as specified in [RFC5321]. change the behavior specified in [RFC5321].
A UTF8SMTPbis aware MUA/MSA sending to a legacy SMTP server [RFC5321] An EAI-aware MUA/MSA sending to a legacy SMTP server [RFC5321] and
and [RFC5322] MAY convert an ASCII@non-ASCII address into the format [RFC5322] MAY convert an ASCII@U-label [RFC5890] address into the
of ASCII@A-label [RFC5890] if the email address is in the format of format of ASCII@A-label [RFC5890] if the email address is in the
ASCII@non-ASCII. format of ASCII@U-label.
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
terms of ASCII characters, using the production for a mailbox and in terms of ASCII characters.
those productions on which it depends.
The key changes made by this specification are, informally, to The key changes made by this specification include:
o Change the definition of "Domain" to permit either the RFC 5321
definition above or a UTF-8 string representing a DNS label that o Change the definition of <Domain> to permit both the RFC 5321
is conformant with IDNA definitions [RFC5890]. definition and a UTF-8 string representing a DNS label that is
o Change the definition of "Local-part" to permit either the conformed with IDNA definitions [RFC5890].
definition above or a UTF-8 string. That string MUST NOT contain o Change the definition of <Local-part> to permit both the RFC 5321
any of the ASCII characters (either graphics or controls) that are definition and a UTF-8 string. That string MUST NOT contain any
not permitted in "atext"; it is otherwise unrestricted. of the ASCII characters (either graphics or controls) that are 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 / address-literal ) uMailbox = uLocal-part "@" ( uDomain / address-literal )
; Replace Mailbox in RFC 5321, Section 4.1.2 ; Replace Mailbox in RFC 5321, Section 4.1.2
address-literal = <See Section 4.1.2 of RFC 5321> address-literal = <Defined in Section 4.1.2 of RFC 5321>
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 5321, Section 4.1.2 ; Replace Local-part in RFC 5321, Section 4.1.2
uDot-string = uAtom *("." uAtom) uDot-string = uAtom *("." uAtom)
; Replace Dot-string in RFC 5321, Section 4.1.2 ; Replace Dot-string in RFC 5321, Section 4.1.2
uAtom = 1*ucharacter uAtom = 1*ucharacter
; Replace Atom in RFC 5321, Section 4.1.2 ; Replace Atom in RFC 5321, Section 4.1.2
ucharacter = atext / UTF8-non-ascii ucharacter = atext / UTF8-non-ascii
atext = <See Section 3.2.3 of RFC 5322> atext = <Defined in Section 3.2.3 of RFC 5322>
; Same definition with atext in RFC 5321, Section 4.1.2
uQuoted-string = DQUOTE *uqcontent DQUOTE uQuoted-string = DQUOTE *uQcontentSMTP DQUOTE
; Replace Quoted-string in RFC 5321, Section 4.1.2 ; Replace Quoted-string in RFC 5321, Section 4.1.2
DQUOTE = <See appendix B.1 of RFC 5234> DQUOTE = <Defined in appendix B.1 of RFC 5234>
uqcontent = qcontent / UTF8-non-ascii uQcontentSMTP = qtextSMTP / quoted-pairSMTP / UTF8-non-ascii
qcontent = <See Section 3.2.4 of RFC 5322> qtextSMTP = <Defined in Section 4.1.2 of RFC 5321>
uDomain = sub-udomain *("." sub-udomain) quoted-pairSMTP = <Defined in Section 4.1.2 of RFC 5321>
; Replace Domain in RFC 5321, Section 4.1.2
sub-udomain = uLet-dig [uLdh-str] uDomain = sub-udomain *("." sub-udomain)
; Replace sub-domain in RFC 5321, Section 4.1.2 ; Replace Domain in RFC 5321, Section 4.1.2
uLet-dig = Let-dig / UTF8-non-ascii sub-udomain = uLet-dig [uLdh-str]
; Replace sub-domain in RFC 5321, Section 4.1.2
Let-dig = <See Section 4.1.2 of RFC 5321> uLet-dig = Let-dig / UTF8-non-ascii
uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-non-ascii) uLet-dig Let-dig = <Defined in Section 4.1.2 of RFC 5321>
; Replace Ldh-str in RFC 5321, Section 4.1.2
UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4 uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-non-ascii) uLet-dig
; Replace Ldh-str in RFC 5321, Section 4.1.2
UTF8-2 = <See Section 4 of RFC 3629> UTF8-non-ascii = <Defined in Section 4.1 of RFC5335bis>
UTF8-3 = <See Section 4 of RFC 3629> 3.4. MAIL Command Parameter Usage
UTF8-4 = <See Section 4 of RFC 3629> If the envelope or message being sent requires the capabilities of
the UTF8SMTPbis extension, the SMTP client MUST supply the
UTF8SMTPbis parameter with the MAIL command. If this parameter is
provided, it MUST have no value. If the SMTP client is aware that
neither the envelope nor the message being sent requires any of the
UTF8SMTPbis extension capabilities, it SHOULD NOT supply the
UTF8SMTPbis parameter with the MAIL command.
The value of "uDomain" SHOULD be verified by IDNA definitions Because there is no guarantee that a next-hop SMTP server will
[RFC5890]. If that verification fails, the email address with that support the UTF8SMTPbis extension, use of the UTF8SMTPbis extension
uDomain MUST NOT be regarded as a valid email address. always carries a risk of transmission failure. In fact, during the
early stages of deployment for the UTF8SMTPbis extension, the risk
will be quite high. Hence there is a distinct near-term advantage
for ASCII-only messages to be sent without using this extension. The
long-term advantage of casting ASCII [ASCII] characters(0x7f and
below) as UTF-8 form is that it permits pure-Unicode environments.
3.4. UTF8 addresses and Response Codes This specification does not require that the EAI-aware SMTP client
inspect the message or otherwise go to extraordinary lengths to
assure itself whether the UTF8SMTPbis extension is REQUIRED for the
particular message.
An internationalized message MUST NOT be sent to an SMTP server that 3.5. Non-ASCII addresses and Reply-codes
does not support UTF8SMTPbis. Such a message should be rejected by a
server if it lacks the support of UTF8SMTPbis.
The three-digit reply codes used in this section are consistent with An EAI-aware SMTP client MUST only send an internationalized message
their meanings as defined in RFC 5321. to an SMTP server that supports UTF8SMTPbis. If the SMTP server does
not support this option, then the EAI-aware SMTP client has three
choices according to section 3.2 of this specification and MAY choose
to reject the internationalized message.
The three-digit Reply-codes used in this section are based on 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 reply-code 553 is returned with the meaning "mailbox
not allowed". When messages are rejected for other reasons, such as name not allowed". When messages are rejected because the MAIL
the MAIL command requiring an ASCII address, the response code 550 is command requires an ASCII address, the reply-code 550 is returned
used with the meaning "mailbox unavailable". When the server with the meaning "mailbox unavailable". When the EAI-aware SMTP
supports enhanced mail system status codes [RFC3463], response code server supports enhanced mail system status codes [RFC3463], reply-
"X.6.7" [RFC5248] is used, meaning that "UTF-8 addresses not code "X.6.7" [RFC5248] is used, meaning that "non-ASCII addresses not
permitted for that sender/recipient". permitted for that sender/recipient".
If the response code is issued after the final "." of the DATA When messages are rejected for other reasons, the server SHOULD
command, the response code "554" is used with the meaning follow the model of the base email specifications [RFC5321]; this
"Transaction failed". When the server supports enhanced mail system extension does not change those circumstances or reply messages.
status codes [RFC3463], response code "X.6.9" [RFC5248] is used,
meaning that "UTF-8 header message can not be transferred to one or
more recipient so the message must be rejected".
3.5. Body Parts and SMTP Extensions If the reply-code is issued after the final "." of the DATA command,
the reply-code "554" is used with the meaning "Transaction failed".
When the EAI-aware SMTP server supports enhanced mail system status
codes [RFC3463], reply-code "X.6.9" [RFC5248] is used, meaning that
"UTF-8 header message can not be transmitted to one or more
recipients, so the message MUST be rejected".
There is no ESMTP parameter to assert that a message is an 3.6. Body Parts and SMTP Extensions
internationalized message. An SMTP server that requires accurate
knowledge of whether a message is internationalized is required to
parse all message header fields and MIME header fields [RFC2045] and
[RFC2047] in the message body.
While this specification requires that servers support the 8BITMIME The MAIL command parameter UTF8SMTPbis asserts that a message is an
extension [RFC1652] to ensure that servers have adequate handling internationalized message or the message being sent needs the
capability for 8-bit data and to avoid a number of complex encoding UTF8SMTPbis support. The message being sent via the MAIL command
problems, the use of internationalized addresses obviously does not with the UTF8SMTPbis parameter has still a chance of that the message
require non-ASCII body parts in the MIME message [RFC2045] and transmitted is not an internationalized message. An EAI-aware SMTP
[RFC2047]. The UTF8SMTPbis extension MAY be used with the client or server that requires accurate knowledge of whether a
BODY=8BITMIME parameter if that is appropriate given the body content message is internationalized needs to parse all message header fields
or, with the BODY=BINARYMIME parameter, if the server advertises and MIME header fields [RFC2045] and [RFC2047] in the message body.
BINARYMIME [RFC3030] and that is appropriate. However, this specification does not require that the SMTP client or
server inspects the message.
Assuming that the server advertises UTF8SMTPbis and 8BITMIME, and While this specification requires that EAI-aware SMTP servers support
receives at least one non-ASCII address, the precise interpretation the 8BITMIME extension [RFC6152] to ensure that servers have adequate
of "BODY=8BITMIME", and "BODY=BINARYMIME" in the MAIL command is: handling capability for 8-bit data and to avoid a number of complex
1. If a BODY=8BITMIME parameter is present, the header contains encoding problems, the use of internationalized email addresses
UTF-8 characters, and some or all of the body parts contain 8-bit obviously does not require non-ASCII body parts in the MIME message
line-oriented data. in RFC 2045 and RFC 2047. The UTF8SMTPbis extension MAY be used with
2. If a BODY=BINARYMIME parameter is present, the header contains the BODY=8BITMIME parameter [RFC6152] if that is appropriate given
UTF-8 characters, and some or all body parts contain binary data the body content or, with the BODY=BINARYMIME parameter, if the SMTP
without restriction as to line lengths or delimiters. server advertises BINARYMIME [RFC3030] and that is appropriate.
3.6. Additional ESMTP Changes and Clarifications 3.7. Additional ESMTP Changes and Clarifications
The information carried in the mail transport process involves The information carried in the mail transport process involves
addresses ("mailboxes") and domain names in various contexts in addresses ("mailboxes") and domain names in various contexts in
addition to the MAIL and RCPT commands and extended alternatives to addition to the MAIL and RCPT commands and extended alternatives to
them. In general, the rule is that, when RFC 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 SMTP extension requires UTF-8 form to be used for the
string; when RFC 5321 specifies a domain name, the name SHOULD be in entire string; when RFC 5321 specifies a domain name, the name SHOULD
the form of A-label if its raw form is non-ASCII. be in the form of A-label if this domain name is an internationalized
domain name[RFC5890].
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 3.7.1. The Initial SMTP Exchange
When an SMTP connection is opened, the server normally sends a When an SMTP connection is opened, the SMTP server sends a "greeting"
"greeting" response consisting of the 220 response code and some response consisting of the 220 reply-code and some information. The
information. The client then sends the EHLO command. Since the SMTP client then sends the EHLO command. Since the SMTP client
client cannot know whether the server supports UTF8SMTPbis until cannot know whether the SMTP server supports UTF8SMTPbis until after
after it receives the response from EHLO, the client must send only it receives the response from EHLO, the EAI-aware SMTP client MUST
ASCII (LDH label [RFC5890] or A-label) domains in the EHLO command send only ASCII (LDH label or A-label [RFC5890] ) domains in the EHLO
and that, if the server provides domain names in the EHLO response, command and that, if the EAI-aware SMTP server provides domain names
they must be in the form of LDH labels or A-labels. in the EHLO response, they MUST be in the form of LDH labels or
A-labels.
3.6.2. Mail eXchangers 3.7.2. Mail eXchangers
Organizations often authorize multiple servers to accept mail If multiple DNS MX records are used to specify multiple servers for a
addressed to them. For example, the organization may itself operate domain in section 5 of [RFC5321], it is strongly advised that all or
more than one server, and may also or instead have an agreement with none of them SHOULD support the UTF8SMTPbis extension. Otherwise,
other organizations to accept mail as a backup. Authorized servers surprising rejections can happen during temporary or permanent
are generally listed in MX records as described in RFC 5321. When failures, which users might perceive as serious reliability issues.
more than one server accepts mail for the domain-part of a mailbox, In order to avoid the possible surprising rejections, the EAI-aware
it is strongly advised that either all or none of them support the email system MAY also implement the advice in EAI addresses advice
UTF8SMTPbis extension. Otherwise, surprising rejections can happen
during temporary failures, which users might perceive as a serious
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 document [EAI addresses] and EAI deployment advice document [EAI
Deployment]. Deployment].
3.6.3. Trace Information 3.7.3. Trace Information
When an SMTP server receives a message for delivery or further For the trace information [RFC5321], this memo updates the time stamp
processing, RFC 5321 requires that it MUST insert trace ("time stamp" line and the return path line [RFC5321] formally defined as follows:
or "Received") information at the beginning of the message content.
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 = uPath / "<>" uReverse-path = uPath / "<>"
; Replace Reverse-path in RFC 5321, section 4.1.2 ; Replace Reverse-path in RFC 5321, section 4.1.2
uPath = "<" [ A-d-l ":" ] uMailbox ">" uPath = "<" [ A-d-l ":" ] uMailbox ">"
; Replace Path in RFC 5321, section 4.1.2 ; Replace Path in RFC 5321, section 4.1.2
; uMailbox is defined in section 3.3 of this document ; uMailbox is defined in section 3.3 of this document
A-d-l = <See section 4.1.2 of RFC 5321> A-d-l = <Defined in 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 [CFWS] ";" 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> From-domain = <Defined in section 4.4 of RFC 5321>
By-domain = <See section 4.4 of RFC 5321> By-domain = <Defined in section 4.4 of RFC 5321>
date-time = <See section 3.3 of RFC 5322> date-time = <Defined in section 3.3 of RFC 5322>
; Same definition with date-time in Section 4.4 of RFC 5321
uOpt-info = [Via] [With] [ID] [uFor] uOpt-info = [Via] [With] [ID] [uFor]
[Additional-Registered-Clauses] [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
Via = <See section 4.4 of RFC 5321> Via = <Defined in section 4.4 of RFC 5321>
With = <See section 4.4 of RFC 5321> With = <Defined in section 4.4 of RFC 5321>
ID = <See section 4.4 of RFC 5321> ID = <Defined in section 4.4 of RFC 5321>
Additional-Registered-Clauses = <See section 4.4 of RFC 5321> Additional-Registered-Clauses = <Defined in section 4.4 of RFC 5321>
uFor = CFWS "FOR" FWS ( uPath / uMailbox) 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
Except in the 'uFor' clause and 'uReverse-path' value where non-ASCII Except in the 'uFor' clause and 'uReverse-path' value where
domain names may be used, internationalized domain names in Received internationalized domain name with the U-label form MAY be used,
fields MUST be transmitted in the form of A-labels. The protocol internationalized domain names in Received fields MUST be transmitted
value of the WITH clause when this extension is used is one of the in the form of A-labels. The protocol value of the WITH clause when
UTF8SMTPbis values specified in the "IANA Considerations" section of this extension is used is one of the UTF8SMTPbis values specified in
this document. the "IANA Considerations" section of this document.
3.6.4. UTF-8 Strings in Replies 3.7.4. UTF-8 Strings in Replies
3.6.4.1. RCPT Commands 3.7.4.1. MAIL and RCPT Commands
If an SMTP client follows this specification and sends any RCPT If an SMTP client follows this specification and sends any MAIL
commands containing non-ASCII addresses, the SMTP server is permitted commands containing the UTF8SMTPbis parameter or any RCPT commands
to use UTF-8 characters in the email address associated with 251 and containing non-ASCII addresses, the EAI-aware SMTP server is
551 response codes, and the client MUST be able to accept and process permitted to use UTF-8 characters in the email address associated
them. If a given RCPT command does not include a non-ASCII envelope with 251 and 551 reply-codes, and the SMTP client MUST be able to
address, the server MUST NOT return a 251 or 551 response containing accept and process them. If a given MAIL command does not include
a non-ASCII mailbox. Instead, it MUST transform such responses into the UTF8SMTPbis parameter or a given RCPT command does not include a
250 or 550 responses that do not contain non-ASCII addresses. non-ASCII envelope address, the EAI-aware SMTP server MUST NOT return
a 251 or 551 response containing a non-ASCII mailbox. Instead, it
MUST transform such responses into 250 or 550 responses that do not
contain non-ASCII addresses.
3.6.4.2. VRFY and EXPN Commands and the UTF8REPLY Parameter 3.7.4.2. VRFY and EXPN Commands and the UTF8SMTPbis Parameter
If the VRFY and EXPN commands are transmitted with the optional If the VRFY and EXPN commands are transmitted with the parameter
parameter "UTF8REPLY", it indicates the client can accept UTF-8 "UTF8SMTPbis", it indicates the SMTP client can accept UTF-8 strings
strings in replies to those commands. This allows the server to use in replies to those commands. This parameter for the VRFY and EXPN
UTF-8 strings in mailbox names and full names that occur in replies commands SHOULD only be used after the SMTP client sees the EHLO
without concern that the client might be confused by them. An SMTP response with the UTF8SMTPbis keyword. This allows the EAI-aware
client that conforms to this specification MUST accept and correctly SMTP server to use UTF-8 strings in mailbox names and full names that
process replies from the VRFY and EXPN commands that contain UTF-8 occur in replies without concern that the SMTP client might be
strings. However, the SMTP server MUST NOT use UTF-8 strings in confused by them. An SMTP client that conforms to this specification
replies if the SMTP client does not specifically allow such replies MUST accept and correctly process replies from the VRFY and EXPN
by transmitting this parameter. Most replies do not require that a commands that contain UTF-8 strings. However, the EAI-aware SMTP
mailbox name be included in the returned text, and therefore UTF-8 is server MUST NOT use UTF-8 strings in replies if the SMTP client does
not needed in them. Some replies, notably those resulting from not specifically allow such replies by transmitting this parameter.
successful execution of the VRFY and EXPN commands, do include the Most replies do not require that a mailbox name be included in the
mailbox, making the provisions of this section important. returned text, and therefore UTF-8 string is not needed in them.
Some replies, notably those resulting from successful execution of
the VRFY and EXPN commands, do include the mailbox.
VERIFY (VRFY) and EXPAND (EXPN) command syntaxes are changed to: VERIFY (VRFY) and EXPAND (EXPN) command syntaxes are changed to:
vrfy = "VRFY" SP ( uLocal-part / uMailbox ) vrfy = "VRFY" SP uString
[ SP "UTF8REPLY" ] CRLF [ SP "UTF8SMTPbis" ] CRLF
; uLocal-part and uMailbox are defined in
; Section 3.3 of this document.
expn = "EXPN" SP ( uLocal-part / uMailbox ) expn = "EXPN" SP uString
[ SP "UTF8REPLY" ] CRLF [ SP "UTF8SMTPbis" ] CRLF
; uLocal-part and uMailbox are defined in
; Section 3.3 of this document.
The "UTF8REPLY" parameter does not use a value. If the reply to a uString = uAtom / uQuoted-string
VERIFY (VRFY) or EXPAND (EXPN) command requires UTF-8, but the SMTP ; uAtom and uQuoted-string are defined in
client did not use the "UTF8REPLY" parameter, then the server MUST ; Section 3.3 of this document.
use either the response code 252 or 550. Response code 252, defined
in [RFC5321], means "Cannot VRFY user, but will accept the message The "UTF8SMTPbis" parameter does not use a value. If the reply to a
and attempt the delivery". Response code 550, also defined in VERIFY (VRFY) or EXPAND (EXPN) command requires UTF-8 string, but the
[RFC5321], means "Requested action not taken: mailbox unavailable". SMTP client did not use the "UTF8SMTPbis" parameter, then the EAI-
When the server supports enhanced mail system status codes [RFC3463], aware SMTP server MUST use either the reply-code 252 or 550. Reply-
the enhanced response code as specified below is used. Using the code 252, defined in [RFC5321], means "Cannot VRFY user, but will
"UTF8REPLY" parameter with a VERIFY (VRFY) or EXPAND (EXPN) command accept the message and attempt the delivery". Reply-code 550, also
enables UTF-8 replies for that command only. defined in [RFC5321], means "Requested action not taken: mailbox
unavailable". When the EAI-aware SMTP server supports enhanced mail
system status codes [RFC3463], the enhanced reply-code as specified
below is used. Using the "UTF8SMTPbis" parameter with a VERIFY
(VRFY) or EXPAND (EXPN) command enables UTF-8 replies for that
command only.
If a normal success response (i.e., 250) is returned, the response If a normal success response (i.e., 250) is returned, the response
MAY include the full name of the user and MUST include the mailbox of MAY include the full name of the user and MUST include the mailbox of
the user. It MUST be in either of the following forms: the user. It MUST be in either of the following forms:
User Name <uMailbox> User Name <uMailbox>
; uMailbox is defined in Section 3.3 of this document. ; uMailbox is defined in Section 3.3 of this document.
; User Name can contain non-ASCII characters. ; User Name can contain non-ASCII characters.
uMailbox uMailbox
; uMailbox is defined in Section 3.3 of this document. ; uMailbox is defined in Section 3.3 of this document.
If the SMTP reply requires UTF-8 strings, but UTF-8 is not allowed in If the SMTP reply requires UTF-8 strings, but UTF-8 string is not
the reply, and the server supports enhanced mail system status codes allowed in the reply, and the EAI-aware SMTP server supports enhanced
[RFC3463], the enhanced response code is "X.6.8" [RFC5248], meaning mail system status codes [RFC3463], the enhanced reply-code is
"A reply containing a UTF-8 string is required to show the mailbox "X.6.8" [RFC5248], meaning "A reply containing a UTF-8 string is
name, but that form of response is not permitted by the client". REQUIRED to show the mailbox name, but that form of response is not
permitted by the SMTP client".
If the SMTP client does not support the UTF8SMTPbis extension, but If the SMTP client does not support the UTF8SMTPbis extension, but
receives a UTF-8 string in a reply, it may not be able to properly receives a UTF-8 string in a reply, it may not be able to properly
report the reply to the user, and some clients might 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 string MUST NOT appear in the reply.
Although UTF-8 is needed to represent email addresses in responses Although UTF-8 form is needed to represent email addresses in
under the rules specified in this section, this extension does not responses under the rules specified in this section, this extension
permit the use of UTF-8 for any other purposes. SMTP servers MUST does not permit the use of UTF-8 string for any other purposes. EAI-
NOT include non-ASCII characters in replies except in the limited aware SMTP servers MUST NOT include non-ASCII characters in replies
cases specifically permitted in this section. except in the limited cases specifically permitted in this section.
4. IANA Considerations 4. IANA Considerations
IANA should add a new value "UTF8SMTPbis" to the SMTP Service IANA SHOULD add a new value "UTF8SMTPbis" to the SMTP Service
Extension subregistry of the Mail Parameters registry, according to Extension subregistry of the Mail Parameters registry, according to
the following data: the following data:
+-------------+---------------------------------+-----------+ +-------------+---------------------------------+-----------+
| Keywords | Description | Reference | | Keywords | Description | Reference |
+-------------+---------------------------------+-----------+ +-------------+---------------------------------+-----------+
| 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 3.5 and 3.7.4.2 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: non-ASCII addresses not permitted
for that sender/recipient for that sender/recipient
Associated basic status code: 550, 553 Associated basic status code: 550, 553
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 non-ASCII addresses are not permitted
Defined: RFC XXXX (Standard track) Defined: RFC XXXX (Standard track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: ima@ietf.org 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 SMTP client
Associated basic status code: 252, 550, 553 Associated basic status code: 252, 550, 553
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 SMTP client.
Defined: RFC XXXX (Standard track) Defined: RFC XXXX (Standard track)
Submitter: Jiankang YAO Submitter: Jiankang YAO
Change controller: ima@ietf.org 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 rejected 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: ima@ietf.org Change controller: ima@ietf.org
Code: X.6.10 Code: X.6.10
Description: This is a duplicate of X.6.8 and Description: This is a duplicate of X.6.8 and
SHOULD be deprecated for further use. SHOULD be deprecated for further use.
The following entries SHOULD be updated or added in the "Mail The following entries SHOULD be updated or added in the "Mail
Transmission Types" registry under the Mail Parameters registry. Transmission Types" registry under the Mail Parameters registry.
+--------------+-------------------------------+--------------------+ +--------------+-------------------------------+--------------------+
| WITH | Description | Reference | | WITH | Description | Reference |
| protocol | | | | protocol | | |
| types | | | | types | | |
+--------------+-------------------------------+--------------------+ +--------------+-------------------------------+--------------------+
| UTF8SMTP | ESMTP with UTF8SMTP | [RFCXXXX] | | UTF8SMTP | ESMTP with UTF8SMTP | [RFCXXXX] |
skipping to change at page 15, line 36 skipping to change at page 17, line 36
| | AUTH | [RFCXXXX] | | | AUTH | [RFCXXXX] |
| UTF8LMTPS | LMTP with UTF8SMTP and | [RFC3207] | | UTF8LMTPS | LMTP with UTF8SMTP and | [RFC3207] |
| | STARTTLS | [RFCXXXX] | | | STARTTLS | [RFCXXXX] |
| UTF8LMTPSA | LMTP with UTF8SMTP and both | [RFC3207] | | UTF8LMTPSA | LMTP with UTF8SMTP and both | [RFC3207] |
| | STARTTLS and LMTP AUTH | [RFC4954] | | | STARTTLS and LMTP AUTH | [RFC4954] |
| | | [RFCXXXX] | | | | [RFCXXXX] |
+--------------+-------------------------------+--------------------+ +--------------+-------------------------------+--------------------+
5. Security Considerations 5. Security Considerations
See the extended security considerations discussion in the framework The extended security considerations discussion in the framework
document [RFC4952bis]. document [RFC4952bis] will be applied here.
More security considerations are discussed below:
Beyond the use inside the email global system (in SMTP envelopes and
message headers), internationalized email addresses will also show up
inside other cases, in particular:
o the logging systems of SMTP transactions and other logs to monitor
the email systems;
o the trouble ticket systems used by Security Teams to manage
security incidents, when an email address is involved;
This will likely require extending support for full UTF-8 also into
these systems, in order to avoid problems, which could cause also
important loss of data, or require to provide an adequate mechanism
to map non-ASCII strings into them.
Another security aspect to be considered is related to the ability by
security team members to quickly understand, read and identify email
addresses from the logs, when they are tracking an incident.
Mechanims to automatically and quickly provide the origin or
ownership of an internationalized email address SHALL be implemented
for use also by log readers which cannot read easily non-ASCII
information.
The SMTP commands VRFY and EXPN are sometimes used in SMTP
transactions where there is no message to transfer (by tools used to
take automated actions in case potential spam messages are
identified). RFC 5321 section 3.5 and 7.3 give some detailed
description of use and possible behaviours. Implementation of
internationalized addrsses can affect also logs and actions by these
tools.
6. Acknowledgements 6. Acknowledgements
This document revised the [RFC5336]document based on the EAI WG's This document revised the [RFC5336]document based on the EAI WG's
discussion result. Many EAI WG members did some tests and discussion result. Many EAI WG members did some tests and
implementations to move this document to the Standard Track document. implementations to move this document to the Standard Track document.
Significant comments and suggestions were received from Xiaodong LEE, Significant comments and suggestions were received from Xiaodong LEE,
Nai-Wen Hsu, Yangwoo KO, Yoshiro YONEYA, and other members of the JET Nai-Wen Hsu, Yangwoo KO, Yoshiro YONEYA, and other members of the JET
team and were incorporated into the specification. Additional team and were incorporated into the specification. Additional
important comments and suggestions, and often specific text, were important comments and suggestions, and often specific text, were
skipping to change at page 16, line 13 skipping to change at page 18, line 44
contributions include material from John C Klensin, Charles Lindsey, contributions include material from John C Klensin, Charles Lindsey,
Dave Crocker, Harald Tveit Alvestrand, Marcos Sanz, Chris Newman, Dave Crocker, Harald Tveit Alvestrand, Marcos Sanz, Chris Newman,
Martin Duerst, Edmon Chung, Tony Finch, Kari Hurtta, Randall Gellens, Martin Duerst, Edmon Chung, Tony Finch, Kari Hurtta, Randall Gellens,
Frank Ellermann, Alexey Melnikov, Pete Resnick, S. Moonesamy, Soobok Frank Ellermann, Alexey Melnikov, Pete Resnick, S. Moonesamy, Soobok
Lee, Shawn Steele, Alfred Hoenes, Miguel Garcia, Magnus Westerlund, Lee, Shawn Steele, Alfred Hoenes, Miguel Garcia, Magnus Westerlund,
and Lars Eggert. Of course, none of the individuals are necessarily and Lars Eggert. Of course, none of the individuals are necessarily
responsible for the combination of ideas represented here. responsible for the combination of ideas represented here.
7. Change History 7. Change History
[[anchor11: RFC Editor: Please remove this section.]] [[anchor14: RFC Editor: Please remove this section.]]
7.1. draft-yao-eai-rfc5336bis: Version 00 7.1. draft-yao-eai-rfc5336bis: Version 00
Applied errata suggested by Alfred Hoenes. Applied errata suggested by Alfred Hoenes.
7.2. draft-ietf-eai-rfc5336bis: Version 00 7.2. draft-ietf-eai-rfc5336bis: Version 00
Applied the changes suggested by the EAI new charter. Applied the changes suggested by the EAI new charter.
7.3. draft-ietf-eai-rfc5336bis: Version 01 7.3. draft-ietf-eai-rfc5336bis: Version 01
skipping to change at page 17, line 13 skipping to change at page 19, line 43
improve the text based on AD and Co-chairs improve the text based on AD and Co-chairs
7.8. draft-ietf-eai-rfc5336bis: Version 06 7.8. draft-ietf-eai-rfc5336bis: Version 06
update the iana consideration update the iana consideration
7.9. draft-ietf-eai-rfc5336bis: Version 07 7.9. draft-ietf-eai-rfc5336bis: Version 07
improve the iana consideration improve the iana consideration
7.10. draft-ietf-eai-rfc5336bis: Version 08
improve the texts
add the mail parameter
add the new section about mail command parameter usage
update the security consideration
8. References 8. References
8.1. Normative References 8.1. Normative References
[ASCII] American National Standards Institute (formerly United [ASCII] American National Standards Institute (formerly United
States of America Standards Institute), "USA Code for States of America Standards Institute), "USA Code for
Information Interchange", ANSI X3.4-1968, 1968. Information Interchange", ANSI X3.4-1968, 1968.
[RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
Crocker, "SMTP Service Extension for 8bit-MIMEtransport",
RFC 1652, July 1994.
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033, [RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033,
October 1996. 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.
[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
skipping to change at page 17, line 46 skipping to change at page 20, line 34
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.
[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.
[RFC4952bis] [RFC4952bis]
Klensin, J. and Y. Ko, "Overview and Framework for Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2010. Internationalized Email", I-D rfc4952bis, September 2010.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[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. and S. Steel, "Internationalized Email Headers", Abel, Y. and S. Steel, "Internationalized Email Headers",
RFC 5335, December 2010. I-D rfc5335bis, March 2011.
[RFC5337bis] [RFC5337bis]
Newman, C. and A. Melnikov, Ed., "Internationalized Hansen, T., Ed., Newman, C., and A. Melnikov, Ed.,
Delivery Status and Disposition Notifications", RFC 5337, "Internationalized Delivery Status and Disposition
August 2008. Notifications", I-D 5337bis, October 2010.
[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.
[RFC6152] Klensin, J., Freed, N., Rose, M., and D. Crocker, "SMTP
Service Extension for 8-bit MIME Transport", STD 71,
RFC 6152, March 2011.
8.2. Informative References 8.2. Informative References
[EAI Deployment] [EAI Deployment]
Yao, J., Lee, X., and S. Steel, "Advice for EAI Yao, J., Lee, X., and S. Steel, "Advice for EAI
deployment", draft 5335, December 2010. deployment", draft eai-deployment, December 2010.
[EAI addresses] [EAI addresses]
Steel, S., Yao, J., and Mark. Davis, "Advice for non-ASCII Steel, S., Yao, J., and Mark. Davis, "Advice for non-ASCII
& ASCII addresses", draft 5335, December 2010. & ASCII addresses", draft eai-address-advice,
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
skipping to change at page 19, line 11 skipping to change at page 21, line 50
[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.
[RFC5336] Yao, J. and W. Mao, "SMTP Extension for Internationalized [RFC5336] Yao, J. and W. Mao, "SMTP Extension for Internationalized
Email Addresses", RFC 5336, September 2008. Email Addresses", RFC 5336, September 2008.
[RFC5598] Crocker, D., "Internet Mail Architecture", RFC 5598,
July 2009.
Authors' Addresses Authors' Addresses
Jiankang YAO Jiankang YAO
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
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