draft-ietf-eai-smtpext-04.txt   draft-ietf-eai-smtpext-05.txt 
Network Working Group J. Yao, Ed. Network Working Group J. Yao, Ed.
Internet-Draft W. Mao, Ed. Internet-Draft W. Mao, Ed.
Expires: September 4, 2007 CNNIC Intended status: Experimental CNNIC
March 3, 2007 Expires: October 11, 2007 April 9, 2007
SMTP extension for internationalized email address SMTP extension for internationalized email address
draft-ietf-eai-smtpext-04.txt draft-ietf-eai-smtpext-05.txt
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Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
Internationalized email address includes two parts, the local part This document specifies the use of SMTP extension for
and the domain part. The ways email addresses are used by protocols internationalized email address delivery. Communication with systems
are different from the ways domain names are used. The most critical that do not implement this specification is specified in another
difference is that emails are delivered through a chain of peering document.
clients and servers while domain names are resolved by name servers
by looking up their own tables. In addition to this, email transport
protocols SMTP and ESMTP provide a negotiation mechanism through
which clients can make decisions for further processing. This
document specifies the use of SMTP extension for internationalized
email address delivery. It also mentions the backward compatible
mechanism for downgrade procedure, as specified in an associated
specification.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Role of this specification . . . . . . . . . . . . . . . . 3 1.1. Role of this specification . . . . . . . . . . . . . . . . 3
1.2. Proposal Context . . . . . . . . . . . . . . . . . . . . . 3 1.2. Proposal Context . . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Mail Transport-level Protocol . . . . . . . . . . . . . . . . 4 2. Mail Transport-level Protocol . . . . . . . . . . . . . . . . 4
2.1. Framework for the Internationalization Extension . . . . . 4 2.1. Framework for the Internationalization Extension . . . . . 4
2.2. The Address Internationalization Service Extension . . . . 5 2.2. The UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5
2.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 5 2.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 6
2.4. The ALT-ADDRESS parameter . . . . . . . . . . . . . . . . 8 2.4. The ALT-ADDRESS parameter . . . . . . . . . . . . . . . . 8
2.5. The Suggestion of the Value of the ALT-ADDRESS 2.5. Using the ALT-ADDRESS parameter . . . . . . . . . . . . . 8
parameter . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 9 2.6. Body Parts and SMTP Extensions . . . . . . . . . . . . . . 9
2.7. Additional ESMTP Changes and Clarifications . . . . . . . 10 2.7. Additional ESMTP Changes and Clarifications . . . . . . . 9
2.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 10 2.7.1. The Initial SMTP Exchange . . . . . . . . . . . . . . 10
2.7.2. Message Retry . . . . . . . . . . . . . . . . . . . . 10 2.7.2. Message Retry . . . . . . . . . . . . . . . . . . . . 10
2.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11 2.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11
2.7.4. Mailing List Question . . . . . . . . . . . . . . . . 12 3. Issues with Other Parts of the Email System . . . . . . . . . 12
2.7.5. POP and IMAP . . . . . . . . . . . . . . . . . . . . . 12 3.1. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.7.6. SMTP Service Extension for DSNs . . . . . . . . . . . 12 3.2. SMTP Service Extension for DSNs . . . . . . . . . . . . . 12
3. Potential problems . . . . . . . . . . . . . . . . . . . . . . 12 3.3. POP and IMAP . . . . . . . . . . . . . . . . . . . . . . . 12
3.1. Impact to RFC 4409 and many email related RFC . . . . . . 13 4. Potential problems . . . . . . . . . . . . . . . . . . . . . . 12
4. Implementation Advice . . . . . . . . . . . . . . . . . . . . 13 4.1. Impact many email related RFC . . . . . . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 5. Implementation Advice . . . . . . . . . . . . . . . . . . . . 13
6. Security considerations . . . . . . . . . . . . . . . . . . . 13 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 7. Security considerations . . . . . . . . . . . . . . . . . . . 13
8. Change History . . . . . . . . . . . . . . . . . . . . . . . . 14 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 14 9. Change History . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 14 9.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 14
8.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 14 9.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 14
8.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 14 9.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 14
8.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 15 9.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . . 15 9.6. draft-ietf-eai-smtpext: Version 05 . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 17 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19
1. Introduction 1. Introduction
Internationalized email address is different from the Internationalized email address includes two parts, the local part
internationalized domain name (IDN). It can be solved by exploiting and the domain part. The ways email addresses are used by protocols
the negotiation mechanism while IDN can not use the negotiation are different from the ways domain names are used. The most critical
mechanism. So internationalized email address SHOULD be solved in difference is that emails are delivered through a chain of peering
the mail transport-level using the negotiation mechanism, which is an clients and servers while domain names are resolved by name servers
architecturally desirable approach. This document specifies a by looking up their own tables. In addition to this, email transport
protocol to solve the problem of internationalized email address protocol ESMTP[RFC1869] provide a negotiation mechanism through which
based on ESMTP. The protocol proposed here is MTA-level solution clients can make decisions for further processing; please see more in
which is feasible, architecturally elegant, and not as difficult to [EAI-framework]. Email addresses can exploit the SMTP extension
be deployed in relevant communities. negotiation mechanism while Internationalized Domain Name(IDN) does
not have such a facility. This is also more desirable
architecturally. This document specifies an SMTP extension to permit
internationalized email addresses in envelopes, and UTF-8 in headers.
The protocol described here is an MTA solution which is feasible,
architecturally elegant, and not difficult to deploy.
1.1. Role of this specification 1.1. Role of this specification
An overview document [EAI-overview] specifies the requirements for, An framework document [EAI-framework] specifies the requirements for,
and components of, full internationalization of electronic mail. and components of, full internationalization of electronic mail. To
understand and implement this specification, understanding the
context presented in [EAI-framework] is necessary.
This document specifies an element of that work, specifically the This document specifies an element of that work, specifically the
definition of an SMTP extension [RFC1869] for the internationalized definition of an SMTP extension [RFC1869] for the internationalized
email address transport delivery. email address transport delivery.
1.2. Proposal Context 1.2. Proposal Context
In order to use internationalized email addresses, we need to
internationalize both the domain part and the local part of the email
address. The domain part of the email address has been
internationalized through IDNA RFC 3490 [RFC3490]. But the local
part of the email address still remains as non-internationalized.
The syntax of Internet email addresses is restricted to a subset of
7-bit ASCII for the domain-part, with a less-restricted subset for
the local-part. These restrictions are specified in RFC 2821
[RFC2821]. To be able to deliver internationalized email through
SMTP servers, we need to upgrade SMTP server to be able to carry the
internationalized email address. Since the older SMTP servers, the
mail-reading clients and other systems that are downstream from them
might not be prepared to handle these extended addresses, an SMTP
extension is specified to identify and protect the addressing
mechanism.
This specification describes a change to the email transport This specification describes a change to the email transport
mechanism that permits non-ASCII address in both the envelope and mechanism that permits non-ASCII characters in both the envelope and
header fields of messages. The context for the change is described header fields of messages while the specification in [EAI-utf8header]
in [EAI-overview] and the details of the header changes are described specifies the details of how and where non-ASCII characters are
in [EAI-utf8header]. permitted in the header fields of messages. The context for the
change is described in [EAI-framework].
1.3. Terminology 1.3. Terminology
The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED", The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED",
and "MAY" in this document are to be interpreted as described in RFC and "MAY" in this document are to be interpreted as described in RFC
2119 [RFC2119]. 2119 [RFC2119].
All specialized terms used in this specification are defined in the All specialized terms used in this specification are defined in the
EAI overview [EAI-overview] or in [RFC2821] and [RFC2822]. The terms EAI framework [EAI-framework] or in [RFC2821] and [RFC2822]. The
"ASCII address", "internationalized email address", "non-ASCII terms "ASCII address", "internationalized email address", "non-ASCII
address", "i18mail address", "UTF8SMTP", "message" and "mailing list" address", "i18mail address", "UTF8SMTP", "message" and "mailing list"
are used with the definitions from the EAI overview document. are used with the definitions from the [EAI-framework] document.
This document defines only those syntax rules that are different from This document defines only those ABNF [RFC4234] syntax rules that are
those of the base email specifications [RFC2821][RFC2822] and, where different from those of the base email specifications
the earlier rules are upgraded or extended, gives them new names. [RFC2821][RFC2822] and, where the earlier rules are upgraded or
When the new rule is a small upgrade to the older one, it is extended, gives them new names. When the new rule is a small upgrade
typically given a name starting with "u". Rules that are undefined to the older one, it is typically given a name starting with "u".
here may be found in the base email documents under the same names. Rules that are undefined here may be found in the base email
documents under the same names.
This document is being discussed on the EAI mailing list. See [[anchor4: RFC EDITOR'S NOTE: The following text should be deleted
https://www1.ietf.org/mailman/listinfo/ima for information about before publication.]] This document is being discussed on the EAI
subscribing. The list's archive is at mailing list. See https://www1.ietf.org/mailman/listinfo/ima for
information about subscribing. The list's archive is at
http://www1.ietf.org/mail-archive/web/ima/index.html. http://www1.ietf.org/mail-archive/web/ima/index.html.
2. Mail Transport-level Protocol 2. Mail Transport-level Protocol
2.1. Framework for the Internationalization Extension 2.1. Framework for the Internationalization Extension
The following service extension is defined: The following service extension is defined:
1. The name of the SMTP service extension is "Email Address 1. The name of the SMTP service extension is "Email Address
Internationalization"; Internationalization";
2. The EHLO keyword value associated with this extension is 2. The EHLO keyword value associated with this extension is
"UTF8SMTP"; "UTF8SMTP";
3. No parameter values are defined for this EHLO keyword value. In 3. No parameter values are defined for this EHLO keyword value. In
order to permit future (although unanticipated) extensions, the order to permit future (although unanticipated) extensions, the
EHLO response MUST NOT contain any parameters for that keyword. EHLO response MUST NOT contain any parameters for that keyword.
If a parameter appears, the SMTP client that is conformant to Clients MUST ignore any parameters, that is, clients MUST behave
this version of this specification MUST treat the ESMTP response as if the parameters do not appear. If a server includes
as if the "UTF8SMTP" keyword did not appear. UTF8SMTP in its EHLO response, it MUST be fully compliant with
4. An optional parameter is added to the SMTP MAIL and RCPT this version of this specification.
commands. The parameter is named as ALT-ADDRESS. The "ALT- 4. One optional parameter, ALT-ADDRESS, is added to the SMTP MAIL
ADDRESS" requires an all-ASCII address as a substitute for the and RCPT commands. ALT-ADDRESS specifies an all-ASCII address
i18mail addresses that we call the primary address; you can learn which can be used as a substitute for the i18mail addresses that
more in [EAI-overview] or [EAI-downgrading]. The value of "ALT- we call the primary address; you can learn more in
ADDRESS" is set by the sender when MUA and the Submission server [EAI-framework] or [EAI-downgrading].
have a communication.
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 SMTP MAIL and RCPT commands
are extended to allow UTF-8 characters in the specified mailbox
address.
8. The mail data is extended on compliance with [EAI-utf8header]
9. The maximum length of a MAIL FROM and RCPT TO command lines is
increased by 396 characters by the possible addition of the ALT-
ADDRESS keyword and value.
2.2. The Address Internationalization Service Extension 2.2. The UTF8SMTP Extension
An SMTP Server that announces this extension MUST be prepared to An SMTP Server that announces this extension MUST be prepared to
accept a UTF-8 string [RFC3629] in any position in which RFC 2821 accept a UTF-8 string [RFC3629] in any position in which RFC 2821
specifies that a "mailbox" MAY appear. That string MUST be parsed specifies that a "mailbox" MAY appear. That string MUST be parsed
only as specified in RFC 2821, i.e., by separating the mailbox into only as specified in RFC 2821, 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
treated as opaque unless the SMTP Server is the final delivery MTA. treated as opaque unless the SMTP Server is the final delivery MTA.
Any domain names that are to be looked up in the DNS MUST first be Any domain names that are to be looked up in the DNS MUST first be
processed into the form as specified in IDNA [RFC3490] by means of processed into the form specified in IDNA [RFC3490] by means of the
the ToASCII() operation unless they are already in that form. Any ToASCII() operation unless they are already in that form. Any domain
domain names that are to be compared to local strings SHOULD be names that are to be compared to local strings SHOULD be checked for
checked for validity and then MUST be compared as specified in validity and then MUST be compared as specified in section 3.4 of
section 3.4 of IDNA. IDNA.
The UTF8SMTP extension is valid on the submission port [RFC4409].
An SMTP Client that receives the UTF8SMTP extension keyword in An SMTP Client that receives the UTF8SMTP extension keyword in
response to the "EHLO" command MAY transmit a mailbox name as an response to the "EHLO" command MAY transmit a mailbox name as an
internationalized string in UTF-8 form and MAY send an internationalized string in UTF-8 form and MAY send an UTF-8 header
internationalized mail header [EAI-utf8header]. It MAY transmit the [EAI-utf8header]. It MAY transmit the domain part of that string in
domain part of that string in either punycode (derived from the IDNA either the form of ACE labels specified in [RFC3490] or UTF-8 form.
process) or UTF-8 form. If it sends the domain in UTF-8 form, the If it sends the domain in UTF-8 form, the Submission SMTP client that
original SMTP client SHOULD first verify that the string is valid for first injects the message into the Internet SHOULD first verify that
a domain name according to IDNA rules. As required by RFC 2821, it the string is valid for a domain name according to IDNA rules. The
MUST not attempt to parse, evaluate, or transform the local part in presence of the UTF8SMTP extension does not change the requirement of
any way if the UTF8SMTP SMTP extension is offered by the server. If RFC 2821 that servers MUST not attempt to parse, evaluate, or
transform the local part in any way. We say that an ASCII address is
"available" for a forwarding path or return path if the address is
all-ASCII or an ALT-ADDRESS parameter is specified for the path. If
the UTF8SMTP SMTP extension is not offered by the Server, the SMTP the UTF8SMTP SMTP extension is not offered by the Server, the SMTP
Client MUST NOT transmit an internationalized address and MUST NOT client MUST NOT transmit an internationalized address and MUST NOT
transmit a mail message which contains internationalized mail headers transmit a mail message which contains internationalized mail headers
[EAI-utf8header]. Instead, it MUST either return the message to the [EAI-utf8header] at any level within it MIME structure. Instead, an
user as undeliverable or replace it with the alternate ASCII address. SMTP client other than the Submission MTA MUST make one of the
If it is replaced, the replacement MUST be the ASCII-only address following three choices:
specified with the ALT-ADDRESS parameter.[EAI-downgrading]. 1. Reject or return the message as undeliverable.
2. Find an alternate route to the destination that permits UTF8SMTP.
3. If and only if an ASCII address is available for the return path
and one or more of the specific forwarding paths being attempted,
downgrade the message to an all-ASCII form as specified in
[EAI-downgrading].
To be able to deliver internationalized email through SMTP servers,
we need to upgrade SMTP server to be able to carry the
internationalized email address. Submission servers [RFC4409] are
permitted to perform a broader range of changes to allow the
internationalized email address. The older SMTP servers, the mail-
reading clients and other systems that are downstream from them might
not be prepared to handle these extended addresses. If a SMTP server
does not support the UTF8SMTP extension, then the SMTP client MUST
NOT, under any circumstances, attempt to send UTF8SMTP message to
this server or attempt to use UTF-8 characters of the MAIL FROM or
RCPT TO commands.
2.3. Extended Mailbox Address Syntax 2.3. Extended Mailbox Address Syntax
RFC 2821, section 4.1.2, defines the syntax of a mailbox entirely in RFC 2821, section 4.1.2, defines the syntax of a mailbox entirely in
terms of ASCII characters, using the production for "Mailbox" and terms of ASCII characters, using the production for "Mailbox" and
those on which it depends. those on which it depends.
The key changes made by this specification are, informally, to The key changes made by this specification are, informally, to
o Change the definition of "sub-domain" to permit either the o Change the definition of "sub-domain" to permit either the
definition above or a UTF-8 string representing a DNS label that definition above or a UTF-8 string representing a DNS label that
is conformant with IDNA [RFC3490]. That label MUST NOT contain is conformant with IDNA [RFC3490].
the characters "@" or ".", even though those characters can
normally be inserted into a DNS label.
o Change the definition of "Atom" to permit either the definition o Change the definition of "Atom" to permit either the definition
above or a UTF-8 string. That string MUST NOT contain any of the above or a UTF-8 string. That string MUST NOT contain any of the
ASCII characters (either graphics or controls) that are not ASCII characters (either graphics or controls) that are not
permitted in "atext"; it is otherwise unrestricted. permitted in "atext"; it is otherwise unrestricted.
According to the description above, define the syntax of an According to the description above, define the syntax of an
internationalized email mailbox with ABNF [RFC4234] as internationalized email mailbox with ABNF [RFC4234] as
uMailbox = uLocal-part "@" uDomain uMailbox = uLocal-part "@" uDomain
; Replace Mailbox in RFC 2821, section 4.1.2 ; Replace Mailbox in RFC 2821, section 4.1.2
uLocal-part = uDot-string / uQuoted-string uLocal-part = uDot-string / uQuoted-string
; MAY be case-sensitive ; MAY be case-sensitive
; Replace Local-part in RFC 2821, section 4.1.2 ; Replace Local-part in RFC 2821, section 4.1.2
uDot-string = uAtom *("." uAtom) uDot-string = uAtom *("." uAtom)
; Replace Dot-string in RFC 2821, section 4.1.2 ; Replace Dot-string in RFC 2821, section 4.1.2
uAtom = 1*ucharacter uAtom = 1*ucharacter
; Replace Atom in RFC 2821, section 4.1.2 ; Replace Atom in RFC 2821, section 4.1.2
ucharacter = atext / UTF8-non-ASCII ucharacter = atext / UTF8-xtra-char
; Replace character in RFC 2821, section 4.1.2 ; Replace character in RFC 2821, section 4.1.2
; atext is defined in RFC 2822 ; atext is defined in RFC 2822
uQuoted-string = DQUOTE *uqcontent DQUOTE uQuoted-string = DQUOTE *uqcontent DQUOTE
; Replace Quoted-string in RFC 2821, section 4.1.2 ; Replace Quoted-string in RFC 2821, section 4.1.2
; DQUOTE is Double Quote defined in RFC 4234 ; DQUOTE is Double Quote defined in RFC 4234
uqcontent = qcontent / UTF8-non-ASCII uqcontent = qcontent / UTF8-xtra-char
; qcontent is defined in RFC 2822, section 3.2.5 ; qcontent is defined in RFC 2822, section 3.2.5
uDomain = (sub-udomain 1*("." sub-udomain)) / address-literal uDomain = (sub-udomain 1*("." sub-udomain)) / address-literal
; Replace Domain in RFC 2821, section 4.1.2 ; Replace Domain in RFC 2821, section 4.1.2
; address-literal is defined in RFC2821 section 4.1.2 ; address-literal is defined in RFC2821 section 4.1.2
sub-udomain = uLet-dig [uLdh-str] sub-udomain = uLet-dig [uLdh-str]
; Replace sub-domain in RFC 2821, section 4.1.2 ; Replace sub-domain in RFC 2821, section 4.1.2
uLet-dig = Let-dig / UTF8-non-ASCII uLet-dig = Let-dig / UTF8-xtra-char
; Let-dig is defined in RFC 2821, section 4.1.3 ; Let-dig is defined in RFC 2821, section 4.1.3
uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-non-ASCII) uLet-dig uLdh-str = *( ALPHA / DIGIT / "-" / UTF8-xtra-char) uLet-dig
; Replace Ldh-str in RFC 2821, section 4.1.3 ; Replace Ldh-str in RFC 2821, section 4.1.3
UTF8-non-ASCII = UTF8-2 / UTF8-3 / UTF8-4 UTF8-xtra-char = UTF8-2 / UTF8-3 / UTF8-4
; UTF8-2, UTF8-3 and UTF8-4 are defined in RFC 3629 ; UTF8-2, UTF8-3 and UTF8-4 are defined in RFC 3629
The value of "udomain" SHOULD be verified with [RFC3490]; If failed, The value of "udomain" SHOULD be verified with IDNA [RFC3490]; If
the email address with that udomain can not be regarded as the valid failed, the email address with that udomain can not be regarded as
email address. the valid email address.
2.4. The ALT-ADDRESS parameter 2.4. The ALT-ADDRESS parameter
If the UTF8SMTP extension is offered, the syntax of the SMTP MAIL and If the UTF8SMTP extension is offered, the syntax of the SMTP MAIL and
RCPT commands is extended to support the optional esmtp-keyword "ALT- RCPT commands is extended to support the optional esmtp-keyword "ALT-
ADDRESS", to specify the conditions under which the SMTP server may ADDRESS", which specifies an alternate all-ASCII address which may be
use ALT-ADDRESS for the possible downgrading. If the ALT-ADDRESS used when downgrading. If the ALT-ADDRESS esmtp-keyword is used, it
esmtp-keyword is used, it MUST have an associated esmtp-value (ALT- MUST have an associated esmtp-value (ALT-ADDRESS-esmtp-value which is
ADDRESS-esmtp-value which is defined below) which requires an all- defined below).
ASCII email address.
Based on the definition of mail-parameters in [RFC2821], the ALT- Based on the definition of mail-parameters in [RFC2821], the ALT-
ADDRESS parameter usage in the commands of "mail from" and "rcpt to" ADDRESS parameter usage in the commands of "mail from" and "rcpt to"
is defined below. is defined below.
"MAIL FROM:" SP <uReverse-path> [ SP <mail-parameters> ]<CRLF> "MAIL FROM:" SP <uReverse-path> [ SP <ALT-ADDRESS-parameter> ]
; Update mail command in RFC 2821, section 3.3 ; Update mail command in RFC 2821, section 3.3
; The syntax for "esmtp-value" in RFC2821
; does not allow "=", SP and control characters.
; Therefore ALT-ADDRESS-paramater is extended.
"RCPT TO:" SP <uForward-path> [ SP <rcpt-parameters> ]<CRLF> "RCPT TO:" SP <uForward-path> [ SP <rcpt-parameters> ]
; Update rcpt command in RFC 2821, section 3.3 ; Update rcpt command in RFC 2821, section 3.3
uReverse-path = uPath uReverse-path = uPath
; Replace Reverse-path in RFC 2821, section 4.1.2 ; Replace Reverse-path in RFC 2821, section 4.1.2
uForward-path = uPath uForward-path = uPath
; Replace Forward-path in RFC 2821, section 4.1.2 ; Replace Forward-path in RFC 2821, section 4.1.2
uPath = "<" [ A-d-l ":" ] uMailbox ">" uPath = "<" [ A-d-l ":" ] uMailbox ">"
; Replace Path in RFC 2821, section 4.1.2 ; Replace Path in RFC 2821, section 4.1.2
; A-d-l is defined in RFC 2821, section 4.1.2 ; A-d-l is defined in RFC 2821, section 4.1.2
; uMailbox is defined in section 2.3 of this document ; uMailbox is defined in section 2.3 of this document
ALT-ADDRESS-esmtp-value=Mailbox ALT-ADDRESS-parameter="ALT-ADDRESS=" ALT-ADDRESS-esmtp-value
; Mailbox is defined in RFC 2821, section 4.1.2
The use of the ALT-ADDRESS is specified below: If some involved SMTP ALT-ADDRESS-esmtp-value=xtext
servers can not support UTF8SMTP capability and if the sender has ; xtext is defined in RFC 3461, section 4.2
already set the ALT-ADDRESS value, the client SMTP server will use
this address as the email address when the SMTP server does the
subsequent operations. If the ALT-ADDRESS value is not set by the
sender, the email must be rejected to the original sender. If the
email is rejected due to the incapability of supporting UTF8SMTP, the
relative server should issue the response error code "5.3.3" defined
in [RFC3463] which means that System is not capable of selected
features, permanent failure.
2.5. The Suggestion of the Value of the ALT-ADDRESS parameter The ALT-ADDRESS-parameter MUST NOT appear more than once in any MAIL
or RCPT command. ALT-ADDRESS-esmtp-value MUST be an all-ASCII email
address before xtext encoding.
The "ALT-ADDRESS" requires an all-ASCII address. There are two 2.5. Using the ALT-ADDRESS parameter
alternative ways to set ALT-ADDRESS value: one is set by the sender
using the all-ASCII address, the other is set using the transformed
email address.
Some may prefer transforming the non-ASCII address to the ASCII A message containing non-ASCII envelope addresses or header fields
Compatible Encoding(ACE) address as the value of the ALT-ADDRESS. A MUST NOT be sent to an SMTP server which does not support UTF8SMTP.
significant obstacle with applying an ACE to all local-parts is that Such a message MAY be rejected due to lack of the ALT-ADDRESS as
the sending or converting system doesn't know if there are some discussed in section 2.2 of this document.
specific data or instructions embedded in the address that the ACE
process would hide. Some SMTP servers may depend on these specific
data or instructions to do some operations while the local parts
applied with ACE will lose or hide these data or instructions. SMTP
[RFC2821] prohibits SMTP relays from converting local parts because
the level of SMTP relays' knowledge on the structure of local parts
is assumed to be zero. However, we can raise the knowledge level by
supplying additional information. Many human users' email addresses
do not have any embedded structure processed by the final delivery
MTA. In that case, the sender can specify that these email addresses
are safe to be converted in the predefined way. The final delivery
SMTP server can revert the addresses even though they are as in all
ASCII form. Unless the MUA or the submission server clearly knows
that the non-ASCII address can be safely transformed into the all-
ASCII address, the non-ASCII address should not be transformed
because transformed email address may cause some potential problems.
This document suggests that the ALT-ADDRESS is set directly by the When messages are rejected because they require UTF8SMTP, response
sender; In default, the all-ASCII address should not be gotten from code "550" is used, defined in [RFC2821], meaning "mailbox
the transformation of the non-ASCII address. unavailable". If enhanced mail system status codes [RFC3463] is
used, the response code should be "5.6.x" [SMTP-codes], meaning that
"alt-address is required but not specified".
[[anchor8: REMOVE THIS: IANA please assign the proper error codes for
"5.6.x".]]
2.6. Body Parts and SMTP Extensions 2.6. Body Parts and SMTP Extensions
While this specification requires that servers support the 8BITMIME Since there is no ESMTP parameter which tells whether the message is
extension [RFC1652] to ensure that servers have adequate handling UTF8SMTP message, SMTP server needs to parse all message header
capability for 8-bit data and to avoid a number of complex encoding fields and MIME header fields in the message body to discover which
problems, the use of internationalized addresses obviously does not messages are UTF8SMTP. While this specification requires that
require non-ASCII body parts in the MIME message. The UTF8SMTP servers support the 8BITMIME extension [RFC1652] to ensure that
extension MAY be used with the BODY=8BITMIME parameter if that is servers have adequate handling capability for 8-bit data and to avoid
appropriate given the body content or, if the server advertises it a number of complex encoding problems, the use of internationalized
and it is appropriate, with the BODY=BINARYMIME parameter specified addresses obviously does not require non-ASCII body parts in the MIME
in [RFC3030]. message. The UTF8SMTP extension MAY be used with the BODY=8BITMIME
parameter if that is appropriate given the body content or, if the
server advertises it and it is appropriate, with the BODY=BINARYMIME
parameter specified in [RFC3030]. This document does not modify the
intent of BODY=BINARYMIME that text body parts and headers must still
be handled in a line-oriented way.
Assuming that the server advertises UTF8SMTP and 8BITMIME, and at Assuming that the server advertises UTF8SMTP and 8BITMIME, and at
least one non-ASCII address, with or without ALT-ADDRESS, the precise least one non-ASCII address, with or without ALT-ADDRESS, the precise
interpretation of these parameters on the MAIL command is: interpretation of these parameters of "No 'Body' parameter", "BODY=
8BITMIME", and "BODY= BINARYMIME" of the MAIL command is:
1. Headers are in UTF-8, body parts are in ASCII. 1. For No "Body" parameter, headers are in UTF-8, body parts are in
2. Headers are in UTF-8, some or all body parts contain 8-bit line- ASCII.
oriented data. 2. For BODY=8BITMIME parameter, headers are in UTF-8, some or all
3. Headers are in UTF-8, some or all body parts contain binary data body parts contain 8-bit line-oriented data.
without restriction as to line lengths or delimiters. 3. For BODY=BINARYMIME parameter, headers are in UTF-8, some or all
body parts contain binary data without restriction as to line
lengths or delimiters.
2.7. Additional ESMTP Changes and Clarifications 2.7. Additional ESMTP Changes and Clarifications
The mail transport process involves addresses ("mailboxes") and The mail transport process involves addresses ("mailboxes") and
domain names in contexts in addition to the MAIL and RCPT commands domain names in contexts in addition to the MAIL and RCPT commands
and extended alternatives to them. In general, the rule is that, and extended alternatives to them. In general, the rule is that,
when RFC 2821 specifies a mailbox, this document expects UTF-8 to be when RFC 2821 specifies a mailbox, this document expects UTF-8 to be
used for the entire string; when RFC 2821 specifies a domain name, used for the entire string; when RFC 2821 specifies a domain name,
the name SHOULD be in punycode form if its raw form is non-ASCII. the name SHOULD be in the form of ACE labels if its raw form is non-
ASCII.
The following subsections list and discuss all of the relevant cases. The following subsections list and discuss all of the relevant cases.
Support and use of this extension requires support for 8BITMIME. It Support and use of this extension requires support for 8BITMIME. It
means that 8BITMIME MUST be advertised by the UTF8SMTP capability means that 8BITMIME MUST be advertised by the UTF8SMTP capability
SMTP server. SMTP server.
2.7.1. The Initial SMTP Exchange 2.7.1. The Initial SMTP Exchange
When an SMTP or ESMTP connection is opened, the server sends a When an SMTP or ESMTP connection is opened, the server normally sends
"banner" response consisting of the 220 reply code and some a "greeting" response consisting of the '220' reply code and some
information. The client then sends the EHLO command. Since the information. The client then sends the EHLO command. Since the
client cannot know whether the server supports UTF8SMTP until after client cannot know whether the server supports UTF8SMTP until after
it receives the response from EHLO, any domain names that appear in it receives the response from EHLO, any domain names that appear in
this dialogue, or in responses to EHLO, MUST be in hostname form, this dialogue, or in responses to EHLO, MUST be in the hostname form,
i.e., internationalized ones MUST be in punycode form. i.e., internationalized ones MUST be in the form of ACE labels.
2.7.2. Message Retry 2.7.2. Message Retry
When an MSA or MTA encounters a server that doesn't support UTF8SMTP An MSA or MTA may encounter a server that doesn't support UTF8SMTP
while relaying a message that requires such support, it is while relaying a message that requires such support. The selection
RECOMMENDED that an alternate MX be tried, and/or the message is of submission servers is presumably under the control of the sender's
client, while the selection of potential intermediate relays is under
the control of the administration of the final delivery server.
Hence, there is a presumption, at least when the recipient address is
non-ASCII, that the delivery path servers normally support UTF8SMTP
(if the sender's client or MSA didn't support UTF8SMTP, the message
would not have been accepted for delivery in the first place). Thus,
a lack of UTF8SMTP support is likely to be a temporary situation. It
is suggested that an alternate MX be tried, and/or the message is
requeued for a later attempt, rather than immediately downgrading or requeued for a later attempt, rather than immediately downgrading or
bouncing. If the message is requeued, the total elapsed time before rejecting. If the message is requeued, the total elapsed time before
bouncing or downgrading SHOULD be smaller than the value used for rejecting or downgrading SHOULD be smaller than the value used for
other SMTP error conditions such as host unreachable or persistent other SMTP error conditions such as host unreachable or persistent
4xx response codes. '4xx' response codes.
An example of such an algorithm:
If a message requires UTF8SMTP but the contacted server doesn't
support it, treat this as a temporary failure if the message has been
queued for less than 24 hours, unless the return-path is non-ASCII
and the forward path is all-ASCII. Normal temporary failure action
is taken, such as, additional address records of the current MX
record are attempted, then additional MX records are attempted, then
the message is requeued with increasing back-off timers.
If message has been queued for less than 24 hours and the message
requires UTF8SMTP support but the contact server doesn't offer this,
the following diagram describes some situations:
return-path forward-path action
----------- ------------ ------
ASCII ASCII reject or downgrade
non-ASCII non-ASCII temp fail
ASCII non-ASCII temp fail
non-ASCII ASCII reject or downgrade
This alternate-MX-or-retry-later technique SHOULD NOT be used when This alternate-MX-or-retry-later technique SHOULD NOT be used when
the message's return path is a non-ASCII address and the specific the message's return path is a non-ASCII address and the specific
forward path being attempted is an ASCII address (because the forward path being attempted is an ASCII address (because the
implication that the delivery path normally supports UTF8SMTP does implication that the delivery path normally supports UTF8SMTP does
not hold in this case). not hold in this case).
The selection of submission servers is presumably under the control
of the sender's client, while the selection of potential intermediate
relays is under the control of the administration of the final
delivery server. Hence, there is a presumption, at least when the
recipient address is non-ASCII, that the delivery path servers
normally support UTF8SMTP (if the sender's client or MSA didn't
support UTF8SMTP, the message would not have been accepted for
delivery in the first place). Thus, a lack of UTF8SMTP support is
likely to be a temporary situation, such as a normal inbound server
being down and a cooperating site acting as a backup MX. If the lack
of UTF8SMTP in the delivery path of a message is a temporary
situation, and the message is sent successfully after retrying, then
it was a good thing to do. Of course, if there is always an ASCII-
only SMTP server in the path, then retrying only adds delay to the
failure (reject or downgrade).
2.7.3. Trace Information 2.7.3. Trace Information
When an SMTP server receives a message for delivery or further When an SMTP server receives a message for delivery or further
processing, it MUST insert trace ("time stamp" or "Received") processing, it MUST insert trace ("time stamp" or "Received")
information at the beginning of the message content. The most information at the beginning of the message content. Time stamp
important use of Received: lines is for debugging mail faults. For appears in the form of "Received: lines". The most important use of
the trace information, we update the time stamp line and the return Received: lines is for debugging mail faults. When the delivery SMTP
path line [RFC2821] formally defined as follows: 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, we update the time stamp line and the
return path line [RFC2821] 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 the section 4.4 of [RFC2821] ; Replaces Return-path-line in the section 4.4 of [RFC2821]
; uReverse-path is defined in Section 2.3 ; uReverse-path is defined in Section 2.3
uTime-stamp-line = "Received:" FWS uStamp <CRLF> uTime-stamp-line = "Received:" FWS uStamp <CRLF>
; Replaces Time-stamp-line in the section 4.4 of [RFC2821] ; Replaces Time-stamp-line in the section 4.4 of [RFC2821]
uStamp = From-domain By-domain uOpt-info ";" FWS date-time uStamp = From-domain By-domain uOpt-info ";" FWS date-time
; Replaces Stamp in the section 4.4 of [RFC2821] ; Replaces Stamp in the section 4.4 of [RFC2821]
uOpt-info = [Via] [With] [ID] [uFor] uOpt-info = [Via] [With] [ID] [uFor]
; Replaces Opt-info in the section 4.4 of [RFC2821] ; Replaces Opt-info in the section 4.4 of [RFC2821]
; [With]'s protocl value will allow UTF8SMTP value ; [With]'s protocl value will allow UTF8SMTP value
uFor = "FOR" FWS 1*( uPath / uMailbox ) CFWS uFor = "FOR" FWS 1*( uPath / uMailbox ) CFWS
; Replaces For in the section 4.4 of [RFC2821] ; Replaces For in the section 4.4 of [RFC2821]
; uReverse-path is defined in Section 2.4 ; uPath is defined in section 2.4 of this document
; uMailbox is defined in section 2.3 of this document
Except in the 'uFor' and 'uReverse-path' line where non-ASCII domain Except in the 'uFor' and 'uReverse-path' line where non-ASCII domain
name may be used, internationalized domain names in Received fields name may be used, internationalized domain names in Received fields
MUST be transmitted in the punycode form. The [With]'s protocl value MUST be transmitted in the form of ACE labels. The protocol value of
will have the value of 'UTF8SMTP' for UTF8SMTP extension. We will the WITH clause is UTF8SMTP when this extension is used. More
give more informaiton about this in "IANA consideration" section of information is in the "IANA Considerations" section of this document,
this document. If a "for" clause containing non-ASCII is encountered below.
when downgrading a message, it is better to just drop the "for"
clause rather than figure out some creative way to encode it. When
only the domain portion of a "for" clause address contains non-ASCII,
this document suggests using the punycode form of the domain portion.
For more detailed information, you may see it in [EAI-utf8header].
2.7.4. Mailing List Question
How a mixture of traditional and internationalized addresses on a
mailing list will impact message flows, error reports, and delivery
notifications in all plausible combinations of UTF8SMTP capability
and un-capability servers is discussed and specified in the
[EAI-mailing list].
2.7.5. POP and IMAP 3. Issues with Other Parts of the Email System
While SMTP mainly takes care of the transportation of messages and 3.1. LMTP
the header fields on wire, POP essentially handles the retrieval of
mail objects from the server by a client. In order to use
internationalized user names based on i18mail for the retrieval of
messages from a mail server using the POP protocol, a new capability
SHOULD be introduced following the POP3 extension mechanism
[RFC2449]. This is discussed and specified in the [EAI-pop].
IMAP [RFC3501] uses the traditional user name which is based on LMTP [RFC2033] may be used as the final delivery agent. In such
ASCII. IMAP SHOULD be updated to support the internationalized user cases, LMTP may be arranged to deliver the mail to the mail store.
names based on i18mail for the retrieval of messages from a mail The mail store may not have UTF8SMTP capability. LMTP need to be
server. This is discussed and specified in the [EAI-imap]. updated to deal with these situations.
2.7.6. SMTP Service Extension for DSNs 3.2. SMTP Service Extension for DSNs
The existing draft standard Delivery status notifications The existing draft standard Delivery status notifications
(DSNs)[RFC3461] is presently limited to US-ASCII text in the machine (DSNs)[RFC3461] is presently limited to US-ASCII text in the machine
readable portions of the protocol. "International Delivery and readable portions of the protocol. "International Delivery and
Disposition Notifications" [EAI-dsn] adds a new address type for Disposition Notifications" [EAI-dsn] adds a new address type for
international email addresses so an original recipient address with international email addresses so an original recipient address with
non-US-ASCII characters can be correctly preserved even after non-US-ASCII characters can be correctly preserved even after
downgrading. If an SMTP server advertises both the UTF8SMTP and the downgrading. If an SMTP server advertises both the UTF8SMTP and the
DSN extension, that server MUST implement EAI-dsn [EAI-dsn] including DSN extension, that server MUST implement EAI-dsn [EAI-dsn] including
support for the ORCPT parameter. support for the ORCPT parameter.
3. Potential problems 3.3. POP and IMAP
3.1. Impact to RFC 4409 and many email related RFC The [EAI-framework] has introduced two documents [EAI-pop] and
[EAI-imap] to how to use internationalized user names based on UTF-8
characters for the retrieval of messages from a mail server.
The internationalized email address protocols will impact on many 4. Potential problems
email related RFC documents such as Message Submission [RFC4409].
Those protocols SHOULD be considered when implementing the
internationalized email address protocols.
4. Implementation Advice 4.1. Impact many email related RFC
Internationalized email has implications for all processes and
protocols which examine, handle, generate, or otherwise deal with
mail. In particular, address parsing or validity checks, message
parsing or handling, etc.
5. Implementation Advice
In the absence of this extension, SMTP clients and servers are In the absence of this extension, SMTP clients and servers are
constrained to using only those addresses permitted by RFC 2821. The constrained to using only those addresses permitted by RFC 2821. The
local parts of those addresses MAY be made up of any ASCII local parts of those addresses MAY be made up of any ASCII
characters, although some of them MUST be quoted as specified there. characters, although some of them MUST be quoted as specified there.
It is notable in an internationalization context that there is a long It is notable in an internationalization context that there is a long
history on some systems of using overstruck ASCII characters (a history on some systems of using overstruck ASCII characters (a
character, a backspace, and another character) within a quoted string character, a backspace, and another character) within a quoted string
to approximate non-ASCII characters. This form of to approximate non-ASCII characters. This form of
internationalization SHOULD be phased out as this extension becomes internationalization SHOULD be phased out as this extension becomes
widely deployed but backward-compatibility considerations require widely deployed but backward-compatibility considerations require
that it continue to be supported. that it continue to be supported.
5. IANA Considerations 6. IANA Considerations
IANA is requested to add "UTF8SMTP" to the SMTP extensions registry IANA is requested to add "UTF8SMTP" to the SMTP extensions registry
with the entry pointing to this specification for its definition. with the entry pointing to this specification for its definition.
IANA is requested to assign the proper error codes "5.6.x" for this
specification based on [SMTP-codes].
The "Mail Transmission Types" registry is requested to be updated to The "Mail Transmission Types" registry is requested to be updated to
include the following new entries: include the following new entries:
WITH protocol types Description Reference WITH protocol types Description Reference
------------------- ---------------------------- --------- ------------------- ---------------------------- ---------
UTF8SMTP UTF8SMTP with Service Extensions [RFCxxxx] UTF8SMTP UTF8SMTP with Service Extensions [RFCxxxx]
UTF8SMTPA UTF8SMTP with SMTP AUTH [RFCxxxx]
UTF8SMTPS UTF8SMTP with STARTTLS [RFCxxxx]
UTF8SMTPSA UTF8SMTP with both STARTTLS and [RFCxxxx]
SMTP AUTH
6. Security considerations [[anchor20: REMOVE THIS: where RFCxxxx represents the future RFC N0.
of this document. When this document is published as RFC and
assigned with a RFC No., "xxxx" should be replaced with 4-digits
No..]]
See the extended security considerations discussion in [EAI-overview] 7. Security considerations
7. Acknowledgements See the extended security considerations discussion in
[EAI-framework]
8. Acknowledgements
Much of the text in the initial version of this document was derived Much of the text in the initial version of this document was derived
or copied from [Klensin-emailaddr] with the permission of the author. or copied from [Klensin-emailaddr] with the permission of the author.
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 document. Special thanks to team and were incorporated into the document. Special thanks to
those contributors for this version of document, those includes (but those contributors for this version of document, those includes (but
not limited to) John C Klensin, Charles Lindsey, Dave Crocker, Harald not limited to) John C Klensin, Charles Lindsey, Dave Crocker, Harald
Tveit Alvestrand, Marcos Sanz, Chris Newman, Martin Duerst, Edmon Tveit Alvestrand, Marcos Sanz, Chris Newman, Martin Duerst, Edmon
Chung, Tony Finch, Kari Hurtta, Randall Gellens, Frank Ellermann. Chung, Tony Finch, Kari Hurtta, Randall Gellens, Frank Ellermann. Of
course, none of the individuals are necessarily responsible for the
combination of ideas represented here.
8. Change History 9. Change History
[[anchor19: REMOVE THIS: This section is used for tracking the update [[anchor23: REMOVE THIS: This section is used for tracking the update
of this document. It may be useful to retain parts of it to of this document. It may be useful to retain parts of it to
facilitate establishing dates and documents for the history of this facilitate establishing dates and documents for the history of this
work.]] work.]]
8.1. draft-ietf-eai-smtpext: Version 00 9.1. draft-ietf-eai-smtpext: Version 00
This version supercedes draft-yao-ima-smtpext-03.txt. It refines the This version supercedes draft-yao-ima-smtpext-03.txt. It refines the
ABNF definiton of the internationalized email address. It represents ABNF definition of the internationalized email address. It
as the EAI working group document. represents as the EAI working group document.
8.2. draft-ietf-eai-smtpext: Version 01 9.2. draft-ietf-eai-smtpext: Version 01
o Upgraded to reflect discussions during IETF 66. o Upgraded to reflect discussions during IETF 66.
o Remove the atomic parameter. o Remove the atomic parameter.
o Add the new section of "the Suggestion of the value of the ALT- o Add the new section of "the Suggestion of the value of the ALT-
ADDRESS parameter". ADDRESS parameter".
8.3. draft-ietf-eai-smtpext: Version 02 9.3. draft-ietf-eai-smtpext: Version 02
o Upgraded to reflect the recent discussion of the ima@ietf.org o Upgraded to reflect the recent discussion of the ima@ietf.org
mailing list. mailing list.
o Add the section of "Body Parts and SMTP Extensions". o Add the section of "Body Parts and SMTP Extensions".
o Add the new section of "Change History". o Add the new section of "Change History".
o Add the subsection about SMTP extensions for DSN. o Add the subsection about SMTP extensions for DSN.
8.4. draft-ietf-eai-smtpext: Version 03 9.4. draft-ietf-eai-smtpext: Version 03
o Update the syntax related to mailbox. o Update the syntax related to mailbox.
o Update the trace field section. o Update the trace field section.
o Add the new section about message retry. o Add the new section about message retry.
o Update the subsection about SMTP extensions for DSN. o Update the subsection about SMTP extensions for DSN.
8.5. draft-ietf-eai-smtpext: Version 04 9.5. draft-ietf-eai-smtpext: Version 04
o Refine some syntax. o Refine some syntax.
o Delete "Message Header Label" section. o Delete "Message Header Label" section.
o Change "bounce" to "reject". o Change "bounce" to "reject".
9. References 9.6. draft-ietf-eai-smtpext: Version 05
9.1. Normative References
[ASCII] Cerf, V., "ASCII format for network interchange", RFC 20,
October 1969.
[EAI-downgrading] o Refine the abstract.
YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading o Delete "The Suggestion of the Value of the ALT-ADDRESS parameter"
mechanism for Internationalized eMail Address (IMA)", section.
draft-ietf-eai-downgrade-02 (work in progress), o Move original section 2.7.4 and 2.7.5 to section 3 with the name
August 2006. "Issues with other parts of the email system".
o Add the new section "LMTP".
o Refine some text according to suggestions from the EAI mailing
list discussion
o Remove the section "Mailing List Question"
[EAI-dsn] Newman, C., "SMTP extensions for DSNs", 10. References
draft-ietf-eai-dsn-00.txt (work in progress), 1 2007.
[EAI-imap] 10.1. Normative References
Resnick, P. and C. Newman, "Considerations for IMAP in
Conjunction with Email Address Internationalization",
draft-ietf-eai-imap-utf8-00 (work in progress), May 2006.
[EAI-mailing list] [ASCII] Cerf, V., "ASCII format for network interchange", RFC 20,
Gellens, R. and E. Chung, "Mailing Lists and October 1969.
Internationalized Email Addresses",
draft-ietf-eai-mailinglist-01.txt (work in progress),
January 2007.
[EAI-overview] [EAI-framework]
Klensin, J. and Y. Ko, "Overview and Framework for Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", draft-ietf-eai-framework-04.txt Internationalized Email", draft-ietf-eai-framework-05.txt
(work in progress), 12 2006. (work in progress), 2 2007.
[EAI-pop] Newman, C., "POP3 Support for UTF-8",
draft-ietf-eai-pop-01.txt (work in progress),
January 2007.
[EAI-utf8header] [EAI-utf8header]
Yeh, J., "Transmission of Email Headers in UTF-8 Yeh, J., "Transmission of Email Headers in UTF-8
Encoding", draft-ietf-eai-utf8headers-01.txt (work in Encoding", draft-ietf-eai-utf8headers-05.txt (work in
progress), August 2006. progress), April 2007.
[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.
[RFC1869] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. [RFC1869] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
Crocker, "SMTP Service Extensions", STD 10, RFC 1869, Crocker, "SMTP Service Extensions", STD 10, RFC 1869,
November 1995. November 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
skipping to change at page 16, line 26 skipping to change at page 16, line 12
[RFC2449] Gellens, R., Newman, C., and L. Lundblade, "POP3 Extension [RFC2449] Gellens, R., Newman, C., and L. Lundblade, "POP3 Extension
Mechanism", RFC 2449, November 1998. Mechanism", RFC 2449, November 1998.
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001. April 2001.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001. April 2001.
[RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission
of Large and Binary MIME Messages", RFC 3030,
December 2000.
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454, Internationalized Strings ("stringprep")", RFC 3454,
December 2002. December 2002.
[RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service [RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service
Extension for Delivery Status Notifications (DSNs)", Extension for Delivery Status Notifications (DSNs)",
RFC 3461, January 2003. 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.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)", "Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003. RFC 3490, March 2003.
[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, March 2003. (IDNA)", RFC 3492, March 2003.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 3629, November 2003. 10646", RFC 3629, November 2003.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005. Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005. Specifications: ABNF", RFC 4234, October 2005.
[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail", 10.2. Informative References
RFC 4409, April 2006.
9.2. Informative References [EAI-downgrading]
YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading
mechanism for Internationalized eMail Address (IMA)",
draft-ietf-eai-downgrade-02 (work in progress),
August 2006.
[EAI-dsn] Newman, C., "SMTP extensions for DSNs",
draft-ietf-eai-dsn-00.txt (work in progress), 1 2007.
[EAI-imap]
Resnick, P. and C. Newman, "Considerations for IMAP in
Conjunction with Email Address Internationalization",
draft-ietf-eai-imap-utf8-01 (work in progress),
March 2007.
[EAI-mailing list]
Gellens, R. and E. Chung, "Mailing Lists and
Internationalized Email Addresses",
draft-ietf-eai-mailinglist-01.txt (work in progress),
January 2007.
[EAI-pop] Newman, C., "POP3 Support for UTF-8",
draft-ietf-eai-pop-01.txt (work in progress),
January 2007.
[Klensin-emailaddr] [Klensin-emailaddr]
Klensin, J., "Internationalization of Email Addresses", Klensin, J., "Internationalization of Email Addresses",
draft-klensin-emailaddr-i18n-03 (work in progress), draft-klensin-emailaddr-i18n-03 (work in progress),
July 2005. July 2005.
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033,
October 1996.
[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.
[RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission
of Large and Binary MIME Messages", RFC 3030,
December 2000.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail",
RFC 4409, April 2006.
[SMTP-codes]
KLensin, J., "An IANA Registry for Extended SMTP Status
Codes", draft-klensin-smtp-code-registry-00 (work in
progress), April 2007.
Authors' Addresses Authors' Addresses
Jiankang YAO (editor) Jiankang YAO (editor)
CNNIC CNNIC
No.4 South 4th Street, Zhongguancun No.4 South 4th Street, Zhongguancun
Beijing Beijing
Phone: +86 10 58813007 Phone: +86 10 58813007
Email: yaojk@cnnic.cn Email: yaojk@cnnic.cn
Wei MAO (editor) Wei MAO (editor)
CNNIC CNNIC
No.4 South 4th Street, Zhongguancun No.4 South 4th Street, Zhongguancun
Beijing Beijing
Phone: +86 10 58813055 Phone: +86 10 58813055
Email: mao@cnnic.cn Email: maowei_ietf@cnnic.cn
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
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