draft-ietf-eai-smtpext-05.txt   draft-ietf-eai-smtpext-06.txt 
Network Working Group J. Yao, Ed. Network Working Group J. Yao, Ed.
Internet-Draft W. Mao, Ed. Internet-Draft W. Mao, Ed.
Intended status: Experimental CNNIC Intended status: Experimental CNNIC
Expires: October 11, 2007 April 9, 2007 Expires: December 8, 2007 June 6, 2007
SMTP extension for internationalized email address SMTP extension for internationalized email address
draft-ietf-eai-smtpext-05.txt draft-ietf-eai-smtpext-06.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 34 skipping to change at page 1, line 34
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."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 11, 2007. This Internet-Draft will expire on December 8, 2007.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document specifies the use of SMTP extension for This document specifies the use of SMTP extension for
internationalized email address delivery. Communication with systems internationalized email address delivery. Communication with systems
that do not implement this specification is specified in another that do not implement this specification is specified in another
skipping to change at page 2, line 16 skipping to change at page 2, line 16
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 . . . . . . . . . . . . . . . . . . . . . . . 3 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 UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5 2.2. The UTF8SMTP Extension . . . . . . . . . . . . . . . . . . 5
2.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 6 2.3. Extended Mailbox Address Syntax . . . . . . . . . . . . . 6
2.4. The ALT-ADDRESS parameter . . . . . . . . . . . . . . . . 8 2.4. The ALT-ADDRESS parameter . . . . . . . . . . . . . . . . 8
2.5. Using the ALT-ADDRESS parameter . . . . . . . . . . . . . 8 2.5. Using the ALT-ADDRESS 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 . . . . . . . 9 2.7. Additional ESMTP Changes and Clarifications . . . . . . . 10
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. Mail eXchangers . . . . . . . . . . . . . . . . . . . 10
2.7.3. Trace Information . . . . . . . . . . . . . . . . . . 11 2.7.3. Trace Information . . . . . . . . . . . . . . . . . . 10
3. Issues with Other Parts of the Email System . . . . . . . . . 12 2.7.4. UTF-8 Reply . . . . . . . . . . . . . . . . . . . . . 11
3.1. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3. Issues with Other Parts of the Email System . . . . . . . . . 13
3.2. SMTP Service Extension for DSNs . . . . . . . . . . . . . 12 3.1. LMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3. POP and IMAP . . . . . . . . . . . . . . . . . . . . . . . 12 3.2. SMTP Service Extension for DSNs . . . . . . . . . . . . . 13
4. Potential problems . . . . . . . . . . . . . . . . . . . . . . 12 3.3. POP and IMAP . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Impact many email related RFC . . . . . . . . . . . . . . 12 4. Potential problems . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Impact many email related RFC . . . . . . . . . . . . . . 13
5. Implementation Advice . . . . . . . . . . . . . . . . . . . . 13 5. Implementation Advice . . . . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Security considerations . . . . . . . . . . . . . . . . . . . 13 7. Security considerations . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
9. Change History . . . . . . . . . . . . . . . . . . . . . . . . 14 9. Change History . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 14 9.1. draft-ietf-eai-smtpext: Version 00 . . . . . . . . . . . . 15
9.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 14 9.2. draft-ietf-eai-smtpext: Version 01 . . . . . . . . . . . . 15
9.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 14 9.3. draft-ietf-eai-smtpext: Version 02 . . . . . . . . . . . . 15
9.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 14 9.4. draft-ietf-eai-smtpext: Version 03 . . . . . . . . . . . . 15
9.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 15 9.5. draft-ietf-eai-smtpext: Version 04 . . . . . . . . . . . . 16
9.6. draft-ietf-eai-smtpext: Version 05 . . . . . . . . . . . . 15 9.6. draft-ietf-eai-smtpext: Version 05 . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9.7. draft-ietf-eai-smtpext: Version 06 . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . . 15 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . . 16 10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Intellectual Property and Copyright Statements . . . . . . . . . . 20
1. Introduction 1. Introduction
Internationalized email address includes two parts, the local part Internationalized email address includes two parts, the local part
and the domain part. The ways email addresses are used by protocols and the domain part. The ways email addresses are used by protocols
are different from the ways domain names are used. The most critical are different from the ways domain names are used. The most critical
difference is that emails are delivered through a chain of peering difference is that emails are delivered through a chain of peering
clients and servers while domain names are resolved by name servers clients and servers while domain names are resolved by name servers
by looking up their own tables. In addition to this, email transport by looking up their own tables. In addition to this, email transport
protocol ESMTP[RFC1869] provide a negotiation mechanism through which protocol ESMTP[RFC1869] provide a negotiation mechanism through which
skipping to change at page 3, line 25 skipping to change at page 3, line 25
[EAI-framework]. Email addresses can exploit the SMTP extension [EAI-framework]. Email addresses can exploit the SMTP extension
negotiation mechanism while Internationalized Domain Name(IDN) does negotiation mechanism while Internationalized Domain Name(IDN) does
not have such a facility. This is also more desirable not have such a facility. This is also more desirable
architecturally. This document specifies an SMTP extension to permit architecturally. This document specifies an SMTP extension to permit
internationalized email addresses in envelopes, and UTF-8 in headers. internationalized email addresses in envelopes, and UTF-8 in headers.
The protocol described here is an MTA solution which is feasible, The protocol described here is an MTA solution which is feasible,
architecturally elegant, and not difficult to deploy. architecturally elegant, and not difficult to deploy.
1.1. Role of this specification 1.1. Role of this specification
An framework document [EAI-framework] specifies the requirements for, The framework document [EAI-framework] specifies the requirements
and components of, full internationalization of electronic mail. To for, and components of, full internationalization of electronic mail.
understand and implement this specification, understanding the To understand and implement this specification, understanding the
context presented in [EAI-framework] is necessary. 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
This specification describes a change to the email transport This specification describes a change to the email transport
mechanism that permits non-ASCII characters in both the envelope and mechanism that permits non-ASCII characters in both the envelope and
skipping to change at page 4, line 42 skipping to change at page 4, line 42
EHLO response MUST NOT contain any parameters for that keyword. EHLO response MUST NOT contain any parameters for that keyword.
Clients MUST ignore any parameters, that is, clients MUST behave Clients MUST ignore any parameters, that is, clients MUST behave
as if the parameters do not appear. If a server includes as if the parameters do not appear. If a server includes
UTF8SMTP in its EHLO response, it MUST be fully compliant with UTF8SMTP in its EHLO response, it MUST be fully compliant with
this version of this specification. this version of this specification.
4. One optional parameter, ALT-ADDRESS, is added to the SMTP MAIL 4. One optional parameter, ALT-ADDRESS, is added to the SMTP MAIL
and RCPT commands. ALT-ADDRESS specifies an all-ASCII address and RCPT commands. ALT-ADDRESS specifies an all-ASCII address
which can be used as a substitute for the i18mail addresses that which can be used as a substitute for the i18mail addresses that
we call the primary address; you can learn more in we call the primary address; you can learn more in
[EAI-framework] or [EAI-downgrading]. [EAI-framework] or [EAI-downgrading].
5. No additional SMTP verbs are defined by this extension. 5. One optional parameter "UTF8REPLY" is added to the VRFY and EXPN
6. Servers offering this extension MUST provide support for, and commands. The parameter UTF8REPLY has no value. The parameter
indicates the SMTP client can accept UTF-8 on replies of the
VRFY and EXPN commands.
6. No additional SMTP verbs are defined by this extension.
7. 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
8. The reverse-path and forward-path of SMTP MAIL and RCPT commands
are extended to allow UTF-8 characters in the specified mailbox are extended to allow UTF-8 characters in the specified mailbox
address. address.
8. The mail data is extended on compliance with [EAI-utf8header] 9. The mail datum is extended in compliance with [EAI-utf8header]
9. The maximum length of a MAIL FROM and RCPT TO command lines is 10. The maximum length of a MAIL and RCPT command lines is increased
increased by 396 characters by the possible addition of the ALT- by 460 characters by the possible addition of the ALT-ADDRESS
ADDRESS keyword and value. keyword and value.
2.2. The UTF8SMTP 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
skipping to change at page 5, line 32 skipping to change at page 5, line 37
validity and then MUST be compared as specified in section 3.4 of validity and then MUST be compared as specified in section 3.4 of
IDNA. IDNA.
The UTF8SMTP extension is valid on the submission port [RFC4409]. 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 UTF-8 header internationalized string in UTF-8 form and MAY send an UTF-8 header
[EAI-utf8header]. It MAY transmit the domain part of that string in [EAI-utf8header]. It MAY transmit the domain part of that string in
either the form of ACE labels specified in [RFC3490] or UTF-8 form. either the form of ACE labels specified in [RFC3490] or UTF-8 form.
If it sends the domain in UTF-8 form, the Submission SMTP client that In the domain part of the mailbox string, if any of the labels are
first injects the message into the Internet SHOULD first verify that intended to be interpreted as non-ASCII (i.e., are IDNs), then the
the string is valid for a domain name according to IDNA rules. The Message Submission Server ("MSA") [RFC4409] MUST take responsibility
presence of the UTF8SMTP extension does not change the requirement of for ensuring that the labels are valid (whether they appear in native
RFC 2821 that servers MUST not attempt to parse, evaluate, or character or ACE form). The presence of the UTF8SMTP extension does
transform the local part in any way. We say that an ASCII address is not change the requirement of RFC 2821 that servers relaying mail
"available" for a forwarding path or return path if the address is MUST not attempt to parse, evaluate, or transform the local part in
all-ASCII or an ALT-ADDRESS parameter is specified for the path. If any way.
the UTF8SMTP SMTP extension is not offered by the Server, the SMTP
If the UTF8SMTP SMTP extension is not offered by the Server, the SMTP
client MUST NOT transmit an internationalized address 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] at any level within it MIME structure. Instead, an [EAI-utf8header] at any level within its MIME structure. Instead, if
SMTP client other than the Submission MTA MUST make one of the an SMTP client (SMTP sender) attempts to transfer a UTF8SMTP message
following three choices: and encounters a server that does not support the extension, it MUST
1. Reject or return the message as undeliverable. make one of the following four choices:
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, 1. If and only if the SMTP client (sender) is a Message Submission
we need to upgrade SMTP server to be able to carry the Server[RFC4409], it MAY, consistent with the general provisions
internationalized email address. Submission servers [RFC4409] are for changes by such servers, rewrite the envelope, headers, or
permitted to perform a broader range of changes to allow the message material to make them entirely ASCII and consistent with
internationalized email address. The older SMTP servers, the mail- the provisions of RFC 2821 [RFC2821] and RFC 2822 [RFC2822].
reading clients and other systems that are downstream from them might 2. Reject the message during the SMTP transaction or generate a
not be prepared to handle these extended addresses. If a SMTP server notification of non-deliverability, as specified in RFC 2821
does not support the UTF8SMTP extension, then the SMTP client MUST [RFC2821] and RFC 3464 [RFC3464]. If the message content can be
NOT, under any circumstances, attempt to send UTF8SMTP message to returned without alteration, content should be returned as
this server or attempt to use UTF-8 characters of the MAIL FROM or specified in 2821 but, if a server is encountered along the
RCPT TO commands. return path that cannot accept UTF8SMTP traffic, the content
should simply be abridged or dropped.
3. Find an alternate route to the destination that permits UTF8SMTP.
That route may be discovered by trying alternate MX hosts (using
preference rules as specified in RFC 2821) or using other means
available to the SMTP-sender.
4. If and only if ASCII addresses are available for all addresses
that appear in the return path and the specific forward paths
being attempted, downgrade the message to an all-ASCII form as
specified in [EAI-downgrading]. An ASCII address is considered
to be "available" for a particular address if the original
address in the envelope is in ASCII or if an ALT-Address
parameter is specified for a UTF8SMTP address.
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
skipping to change at page 8, line 15 skipping to change at page 8, line 15
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", which specifies an alternate all-ASCII address which may be ADDRESS", which specifies an alternate all-ASCII address which may be
used when downgrading. If the ALT-ADDRESS esmtp-keyword is used, it used when downgrading. If the ALT-ADDRESS esmtp-keyword is used, it
MUST have an associated esmtp-value (ALT-ADDRESS-esmtp-value which is MUST have an associated esmtp-value (ALT-ADDRESS-esmtp-value which is
defined below). defined below).
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" and "RCPT" is
is defined below. defined below.
"MAIL FROM:" SP <uReverse-path> [ SP <ALT-ADDRESS-parameter> ] "MAIL FROM:" ("<>" / uReverse-path) [ SP Mail-parameters ] CRLF
; Update mail command in RFC 2821, section 3.3 ; Update mail command in RFC 2821, section 4.1.1.2.
; The syntax for "esmtp-value" in RFC2821 ; A new parameter defined by the ABNF non-terminal
; does not allow "=", SP and control characters. ; <ALT-ADDRESS-parameter> is added. It complies
; Therefore ALT-ADDRESS-paramater is extended. ; with the syntax specified by <esmtp-param>.
"RCPT TO:" SP <uForward-path> [ SP <rcpt-parameters> ] "RCPT TO:" ("<Postmaster@" domain ">" / "<Postmaster>" /
; Update rcpt command in RFC 2821, section 3.3 uForward-Path) [ SP Rcpt-parameters ] CRLF
; Update rcpt command in RFC 2821, section 4.1.1.3.
; A new parameter defined by the ABNF non-terminal
; <ALT-ADDRESS-parameter> is added. It complies
; with the syntax specified by <esmtp-param>.
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-parameter="ALT-ADDRESS=" ALT-ADDRESS-esmtp-value ALT-ADDRESS-parameter="ALT-ADDRESS=" ALT-ADDRESS-esmtp-value
ALT-ADDRESS-esmtp-value=xtext ALT-ADDRESS-esmtp-value=xtext
; xtext is defined in RFC 3461, section 4.2 ; Mailbox encoded as xtext.
; xtext is defined in RFC 3461 [RFC3461], section 4.2
The ALT-ADDRESS-parameter MUST NOT appear more than once in any MAIL The ALT-ADDRESS-parameter MUST NOT appear more than once in any MAIL
or RCPT command. ALT-ADDRESS-esmtp-value MUST be an all-ASCII email or RCPT command. ALT-ADDRESS-esmtp-value MUST be an all-ASCII email
address before xtext encoding. address before xtext encoding.
2.5. Using the ALT-ADDRESS parameter 2.5. Using the ALT-ADDRESS parameter
A message containing non-ASCII envelope addresses or header fields A message containing non-ASCII envelope addresses or header fields
MUST NOT be sent to an SMTP server which does not support UTF8SMTP. MUST NOT be sent to an SMTP server which does not support UTF8SMTP.
Such a message MAY be rejected due to lack of the ALT-ADDRESS as Such a message MAY be rejected due to lack of the ALT-ADDRESS as
discussed in section 2.2 of this document. discussed in section 2.2 of this document.
When messages are rejected because they require UTF8SMTP, response When messages are rejected because they require UTF8SMTP, response
code "550" is used, defined in [RFC2821], meaning "mailbox code "550" is used, defined in [RFC2821], meaning "mailbox
unavailable". If enhanced mail system status codes [RFC3463] is unavailable". If enhanced mail system status codes [RFC3463] is
used, the response code should be "5.6.x" [SMTP-codes], meaning that used, the response code should be "5.6.x" [SMTP-codes], meaning that
"alt-address is required but not specified". "alt-address is required but not specified".
If the response code is issued after the final "." of the DATA
command, the response code "554" is used, defined in [RFC2821],
meaning "Transaction failed". if enhanced mail system status codes
[RFC3463] is used, the response code should be "5.6.z" [SMTP-codes],
meaning that "UTF8SMTP downgrade failed".
[[anchor8: REMOVE THIS: IANA please assign the proper error codes for [[anchor8: REMOVE THIS: IANA please assign the proper error codes for
"5.6.x".]] "5.6.x" and "5.6.z".]]
2.6. Body Parts and SMTP Extensions 2.6. Body Parts and SMTP Extensions
Since there is no ESMTP parameter which tells whether the message is Since there is no ESMTP parameter which tells whether the message is
UTF8SMTP message, SMTP server needs to parse all message header UTF8SMTP message, SMTP server needs to parse all message header
fields and MIME header fields in the message body to discover which fields and MIME header fields in the message body to discover which
messages are UTF8SMTP. While this specification requires that messages are UTF8SMTP. While this specification requires that
servers support the 8BITMIME extension [RFC1652] to ensure that servers support the 8BITMIME extension [RFC1652] to ensure that
servers have adequate handling capability for 8-bit data and to avoid servers have adequate handling capability for 8-bit data and to avoid
a number of complex encoding problems, the use of internationalized a number of complex encoding problems, the use of internationalized
addresses obviously does not require non-ASCII body parts in the MIME addresses obviously does not require non-ASCII body parts in the MIME
message. The UTF8SMTP extension MAY be used with the BODY=8BITMIME message. The UTF8SMTP extension MAY be used with the BODY=8BITMIME
parameter if that is appropriate given the body content or, if the parameter if that is appropriate given the body content or, if the
server advertises it and it is appropriate, with the BODY=BINARYMIME server advertises it and it is appropriate, with the BODY=BINARYMIME
parameter specified in [RFC3030]. This document does not modify the parameter specified in [RFC3030].
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 of "No 'Body' parameter", "BODY= interpretation of "No 'Body' parameter", "BODY= 8BITMIME", and "BODY=
8BITMIME", and "BODY= BINARYMIME" of the MAIL command is: BINARYMIME" in the MAIL command is:
1. For No "Body" parameter, headers are in UTF-8, body parts are in 1. For No "Body" parameter, headers are in UTF-8, body parts are in
ASCII. ASCII.
2. For BODY=8BITMIME parameter, headers are in UTF-8, some or all 2. For BODY=8BITMIME parameter, headers are in UTF-8, some or all
body parts contain 8-bit line-oriented data. body parts contain 8-bit line-oriented data.
3. For BODY=BINARYMIME parameter, headers are in UTF-8, some or all 3. For BODY=BINARYMIME parameter, headers are in UTF-8, some or all
body parts contain binary data without restriction as to line body parts contain binary data without restriction as to line
lengths or delimiters. 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
skipping to change at page 10, line 9 skipping to change at page 10, line 22
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 the form of ACE labels if its raw form is non- the name SHOULD be in the form of ACE labels if its raw form is non-
ASCII. 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 capable SMTP
SMTP server. 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 normally sends When an SMTP or ESMTP connection is opened, the server normally sends
a "greeting" 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 the hostname form, this dialogue, or in responses to EHLO, MUST be in the hostname form,
i.e., internationalized ones MUST be in the form of ACE labels. i.e., internationalized ones MUST be in the form of ACE labels.
2.7.2. Message Retry 2.7.2. Mail eXchangers
An MSA or MTA may encounter a server that doesn't support UTF8SMTP
while relaying a message that requires such support. 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. It
is suggested that an alternate MX be tried, and/or the message is
requeued for a later attempt, rather than immediately downgrading or
rejecting. If the message is requeued, the total elapsed time before
rejecting or downgrading SHOULD be smaller than the value used for
other SMTP error conditions such as host unreachable or persistent
'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 Commonly, organizations authorize multiple servers to accept mail
the message's return path is a non-ASCII address and the specific addressed to them. For example, the organization may itself operate
forward path being attempted is an ASCII address (because the more than one server, and may also or instead have an agreement with
implication that the delivery path normally supports UTF8SMTP does other organizations to accept mail as a backup. Authorized servers
not hold in this case). are generally listed in MX records [RFC2821]. When more than one
server accepts mail for the domain-part of a Mailbox, it is strongly
advised that either all or none of them support the UTF8SMTP
extension. Otherwise, surprising downgrades can happen during
temporary failures, which is not a good thing.
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. Time stamp information at the beginning of the message content. Time stamp
appears in the form of "Received: lines". The most important use of appears in the form of "Received: lines". The most important use of
Received: lines is for debugging mail faults. When the delivery SMTP Received: lines is for debugging mail faults. When the delivery SMTP
server makes the "final delivery" of a message, it inserts a return- 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 path line at the beginning of the mail data. The primary purpose of
skipping to change at page 11, line 46 skipping to change at page 11, line 24
; 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 protocol value will allow UTF8SMTP value
uFor = "FOR" FWS 1*( uPath / uMailbox ) CFWS uFor = "FOR" 1*( FWS (uPath / uMailbox) ) CFWS
; Replaces For in the section 4.4 of [RFC2821] ; Replaces For in the section 4.4 of [RFC2821]
; uPath is defined in section 2.4 of this document ; uPath is defined in section 2.4 of this document
; uMailbox is defined in section 2.3 of this document ; uMailbox is defined in section 2.3 of this document
[[anchor12: Note: Whether the FOR parameter is permitted to accept
more than one address is now under discussion as part of the
rfc2821bis effort. The multiple-address construction was introduced
with RFC 2821; it is not clear that it has been widely implemented or
that it is wise. Whatever decision is reached about RFC2821bis will
be reflected in the syntax of a future version 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 form of ACE labels. The protocol value of MUST be transmitted in the form of ACE labels. The protocol value of
the WITH clause is UTF8SMTP when this extension is used. More the WITH clause is UTF8SMTP when this extension is used. More
information is in the "IANA Considerations" section of this document, information is in the "IANA Considerations" section of this document.
below.
2.7.4. UTF-8 Reply
If the client issues the "RCPT" command which contains non-ASCII
characters, the SMTP server is permitted to use UTF-8 characters
within 251 and 551 response codes. Servers MUST NOT include non-
ASCII characters except in the limited cases specifically permitted
in this section.
If the VRFY and EXPN commands has the optional parameter "UTF8REPLY",
it indicates the client can accept UTF-8 on replies of the VRFY and
EXPN commands. Specially this allows to use UTF-8 on mailboxes and
full names which occur on replies. The SMTP client following this
specification MUST accept UTF-8 on replies of the VRFY and EXPN
commands. However the SMTP server MUST not use UTF-8 on replies, if
SMTP client does not ask UTF-8 replies. Some replies include the
mailbox, but usually most of replies do not require that the mailbox
is included in it and therefore UTF-8 is not needed. UTF8REPLY
parameter on the VRFY and EXPN commands tells the SMTP server that
the client is prepared for UTF-8 on SMTP replies.
VERIFY (VRFY) and EXPAND (EXPN)command syntaxes are changed to:
"VRFY" SP uAtom [SP "UTF8REPLY"] CRLF;
;uAtom is defined in section 2.3 of this document
"EXPN" SP uAtom [SP "UTF8REPLY"] CRLF;
;uAtom is defined in section 2.3 of this document
This parameter "UTF8REPLY" does not have value. If SMTP reply
requires UTF-8, but SMTP client does not use "UTF8REPLY" parameter in
the VERIFY (VRFY) and EXPAND (EXPN) commands, the response code "252"
is used, defined in [RFC2821], meaning "Cannot VRFY user, but will
accept the message and attempt the delivery". If enhanced mail
system status code [RFC3463] is used, the response code should be
"5.6.y" or "2.6.y" [SMTP-codes], meaning that "The UTF-8 reply
required, but the UTF8REPLY parameter not used.". [[anchor13: REMOVE
THIS: IANA please assign the proper error codes for "5.6.y" and
"2.6.y".]] "UTF8REPLY" on the VERIFY (VRFY) or EXPAND (EXPN)
commands enables UTF-8 for that command only.
The uAtom of the VRFY and EXPN commands is a user name or a user name
and a domain (see below). If a normal (i.e., 250) response is
returned, the response 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:
User Name <uMailbox>
; uMailbox is defined in section 2.3 of this document
; User Name allows the non-ASCII character.
uMailbox
; uMailbox is defined in section 2.3 of this document
If the SMTP Client lack of the UTF8SMTP support receives the UTF-8
message on reply, it may crash. UTF-8 messages on reply are only
allowed in the commands under the situations described above. Under
any other circumstances, UTF-8 messages on the reply MUST NOT be
used.
3. Issues with Other Parts of the Email System 3. Issues with Other Parts of the Email System
3.1. LMTP 3.1. LMTP
LMTP [RFC2033] may be used as the final delivery agent. In such LMTP [RFC2033] may be used as the final delivery agent. In such
cases, LMTP may be arranged to deliver the mail to the mail store. cases, LMTP may be arranged to deliver the mail to the mail store.
The mail store may not have UTF8SMTP capability. LMTP need to be The mail store may not have UTF8SMTP capability. LMTP need to be
updated to deal with these situations. updated to deal with these situations.
skipping to change at page 13, line 24 skipping to change at page 14, line 18
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.
6. 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 IANA is requested to assign the proper error codes "5.6.x", "5.6.z",
specification based on [SMTP-codes]. "5.6.y" and "2.6.y" 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 [RFC2554bis]
[RFCxxxx]
UTF8SMTPS UTF8SMTP with STARTTLS [RFC3207]
[RFCxxxx]
UTF8SMTPSA UTF8SMTP with both STARTTLS and [RFC3207]
SMTP AUTH [RFC2554bis]
[RFCxxxx]
[[anchor20: REMOVE THIS: where RFCxxxx represents the future RFC N0. [[anchor22: REMOVE THIS: where RFCxxxx represents the future RFC N0.
of this document. When this document is published as RFC and of this document. When this document is published as RFC and
assigned with a RFC No., "xxxx" should be replaced with 4-digits assigned with a RFC No., "xxxx" should be replaced with 4-digits No..
No..]] "RFC2554bis" should be replaced with the new RFC No. when the
"RFC2554bis" document is assigned with the new RFC No.]]
7. Security considerations 7. Security considerations
See the extended security considerations discussion in See the extended security considerations discussion in
[EAI-framework] [EAI-framework]
8. Acknowledgements 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.
skipping to change at page 14, line 4 skipping to change at page 15, line 9
7. Security considerations 7. Security considerations
See the extended security considerations discussion in See the extended security considerations discussion in
[EAI-framework] [EAI-framework]
8. Acknowledgements 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. Of Chung, Tony Finch, Kari Hurtta, Randall Gellens, Frank Ellermann,
course, none of the individuals are necessarily responsible for the Alexey Melnikov. Of course, none of the individuals are necessarily
combination of ideas represented here. responsible for the combination of ideas represented here.
9. Change History 9. Change History
[[anchor23: REMOVE THIS: This section is used for tracking the update [[anchor25: 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.]]
9.1. 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 definition of the internationalized email address. It ABNF definition of the internationalized email address. It
represents as the EAI working group document. represents as the EAI working group document.
skipping to change at page 15, line 23 skipping to change at page 16, line 27
o Refine the abstract. o Refine the abstract.
o Delete "The Suggestion of the Value of the ALT-ADDRESS parameter" o Delete "The Suggestion of the Value of the ALT-ADDRESS parameter"
section. section.
o Move original section 2.7.4 and 2.7.5 to section 3 with the name o Move original section 2.7.4 and 2.7.5 to section 3 with the name
"Issues with other parts of the email system". "Issues with other parts of the email system".
o Add the new section "LMTP". o Add the new section "LMTP".
o Refine some text according to suggestions from the EAI mailing o Refine some text according to suggestions from the EAI mailing
list discussion list discussion
o Remove the section "Mailing List Question" o Remove the section "Mailing List Question"
9.7. draft-ietf-eai-smtpext: Version 06
o Delete the section about message retry.
o Add the new subsection about Mail eXchangers
o Add the new section about "UTF-8 Reply"
o Refine some response code for the section "Using the ALT-ADDRESS
parameter"
10. References 10. References
10.1. Normative References 10.1. Normative References
[ASCII] Cerf, V., "ASCII format for network interchange", RFC 20, [ASCII] Cerf, V., "ASCII format for network interchange", RFC 20,
October 1969. October 1969.
[EAI-framework] [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-05.txt Internationalized Email", draft-ietf-eai-framework-05.txt
skipping to change at page 15, line 51 skipping to change at page 17, line 16
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
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2449] Gellens, R., Newman, C., and L. Lundblade, "POP3 Extension
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.
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
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.
[RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format
for Delivery Status Notifications", RFC 3464,
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
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, 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
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.
10.2. Informative References 10.2. Informative References
[EAI-downgrading] [EAI-downgrading]
YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading
mechanism for Internationalized eMail Address (IMA)", mechanism for Internationalized eMail Address (IMA)",
draft-ietf-eai-downgrade-02 (work in progress), draft-ietf-eai-downgrade-02 (work in progress),
August 2006. August 2006.
skipping to change at page 17, line 27 skipping to change at page 18, line 29
January 2007. 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, [RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033,
October 1996. October 1996.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2554bis]
Extensions (MIME) Part One: Format of Internet Message Siemborski, R. and A. Melnikov, "SMTP Service Extension
Bodies", RFC 2045, November 1996. for Authentication", draft-siemborski-rfc2554bis-09 (work
in progress), April 2007.
[RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission [RFC3030] Vaudreuil, G., "SMTP Service Extensions for Transmission
of Large and Binary MIME Messages", RFC 3030, of Large and Binary MIME Messages", RFC 3030,
December 2000. December 2000.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION [RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over
4rev1", RFC 3501, March 2003. Transport Layer Security", RFC 3207, February 2002.
[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.
[SMTP-codes] [SMTP-codes]
KLensin, J., "An IANA Registry for Extended SMTP Status KLensin, J., "An IANA Registry for Extended SMTP Status
Codes", draft-klensin-smtp-code-registry-00 (work in Codes", draft-klensin-smtp-code-registry-00 (work in
progress), April 2007. progress), April 2007.
Authors' Addresses Authors' Addresses
 End of changes. 45 change blocks. 
162 lines changed or deleted 223 lines changed or added

This html diff was produced by rfcdiff 1.33. The latest version is available from http://tools.ietf.org/tools/rfcdiff/