Network Working Group                     A. Melnikov, Messaging Direct
Internet Draft
Document: draft-melnikov-smtp-lang-00.txt                     June 1999


                          SMTP Language Extension


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  Internet-Drafts are
   working documents of the Internet Engineering Task Force (IETF), its
   areas, and its working groups.  Note that other groups may also
   distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
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   at any time.  It is inappropriate to use Internet- Drafts as
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
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   This document  suggests  a  proposed  protocol  for  the   Internet
   community,    and   requests   discussion   and   suggestions   for
   improvements. Distribution of this draft is unlimited.

   The protocol discussed in this document is experimental and subject
   to change.  Persons planning on either implementing or using this
   protocol are STRONGLY URGED to get in touch with the author before
   embarking on such a project.


1. Abstract

   The Simple Mail Transfer Protocol [RFC-821] allows server
   responses to include human-readable text that in many cases needs to
   be presented to the user.  This document specifies a way for a
   client to negotiate which language the server should use when
   sending human-readable text.


2. Conventions used in this document

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.   If such lines are wrapped without a new "C:"
   or "S:" label, then the wrapping is for editorial clarity and is not
   part of the command.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in [KEYWORDS].


3. Framework for the Language SMTP service extension

   The Language SMTP  service  extension  uses the  SMTP  service  extension  
   mechanism described in [ESMTP].  The following SMTP service extension is 
   therefore defined:

  (1) The name of the SMTP service extension is "Language".

  (2) The EHLO keyword value associated with this service extension is
      "LANGUAGE".

  (3) The AUTH EHLO keyword contains as a parameter a space separated
      list of the names of supported language tags. This list is optional. 
      If the language tag argument is omitted, this means that server is 
      unable to enumerate the list of languages it supports.

  (4) A new SMTP verb "LANG" is defined

  (5) No additional SMTP parameters to either MAIL FROM or RCPT TO commands 
      are defined by this extension.


4. Requirements

   A server that supports this extension SHOULD use the language "i-
   default" as described in [CHARSET-POLICY] as its default language
   until another supported language is negotiated by the client.  A
   server MUST support and include "i-default" in EHLO response.


5. LANG Command

   LANG [language-tag]

     Arguments:
         Zero or one language tag as defined by [RFC-1766].

     Restrictions:
         The LANG command is permitted throughout a mail connection.

     Reply Codes:
         Success:
            250 LANG command completed successfully
         Error: 
            504 Language tag is unknown
            421 <domain> Service not available, closing transmission channel

     Discussion:
         The LANG command requests that human-readable text emitted by
         the server be localized to the language specified in the language
         tag argument.

         If the command succeeds, the server will return human-readable
         responses in the specified language starting with the successful
         250 response to the LANG command.  These responses will be in UTF-8
         [RFC-2044]. In particular, LANG command MAY affect the result of 
         a HELP command.

         If the command fails, the server will continue to return human-
         readable responses in the language it was previously using.

     Example:

        < The server defaults to using English responses until the user
          explicitly changes the language. >

         S: 220 smtp.example.com ESMTP server ready
         C: EHLO main.example.com
         S: 250-smtp.example.com
         S: 250-AUTH CRAM-MD5 DIGEST-MD5
         S: 250 LANGUAGE EN DE RU i-default

         C: HELP
         S: 214-This is Sendmail version X.X.X
         S: 214-Topics:
         S: 214-    HELO    EHLO    MAIL    RCPT    DATA
         S: 214-    RSET    NOOP    QUIT    HELP    VRFY
         S: 214-    EXPN    VERB    ETRN    DSN
         S: 214-For more info use "HELP <topic>".
         S: 214 End of HELP info

        < Once the client changes the language, all responses will be in
          that language starting with 250 response to the LANG command. >

         C: LANG FR
         S: 250 La Language commande a ete executee avec success

         C: HELP
         S: 214-C'est le programme Sendmail version X.X.X
         S: 214-Topics:
         S: 214-    HELO    EHLO    MAIL    RCPT    DATA
         S: 214-    RSET    NOOP    QUIT    HELP    VRFY
         S: 214-    EXPN    VERB    ETRN    DSN
         S: 214-Pour obtenir l'information supplementaire utiliser "HELP <topic>".
         S: 214 La fin de l'information 

        < If a server does not support the requested language, responses
          will continue to be returned in the current language the server is
          using. >

         C: LANG DE
         S: 250 Ce Language n'est pas supporte


5. Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) as described in [ABNF].

   Except as noted otherwise, all alphabetic characters are case-
   insensitive.  The use of upper or lower case characters to define
   token strings is for editorial clarity only.  Implementations MUST
   accept these strings in a case-insensitive fashion.

   CR              = %x0C           ;; ASCII CR, carriage return

   CRLF            = CR LF

   LF              = %x0A           ;; ASCII LF, line feed

   SPACE           = %x20           ;; ASCII SP, space

   LANG_Command = "LANG" SPACE language_tag CRLF

   LANGUAGE_List = "LANGUAGE" *(SPACE <language_tag>) CRLF
      ; Note: the server is required to support the language i-default
      ; and as such i-default must appear in the language response.
      ; When "i-default" is used, all responses MUST contain only 
      ; English text.

   language_tag =  <language_tag> as defined in [RFC-1766]


6. Security Considerations

   This extension allows the negotiation of a language for the human-
   readable text returned by a server.  A user is able to query the
   languages that a server supports.


7. References

   [RFC-821], Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
   821, August 1982, <ftp://ftp.isi.edu/in-notes/rfc821.txt>

   [RFC-1766], Alvestrand, H., "Tags for the Identification of
   Languages", RFC 1766, UNINETT, March 1995,
   <ftp://ftp.isi.edu/in-notes/rfc1766.txt>

   [RFC-2044], Yergeau, F., "UTF-8, a transformation format of Unicode
   and ISO 10646, RFC 2044, Alis Technologies, October 1996,
   <ftp://ftp.isi.edu/in-notes/rfc2044.txt>

   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
   Requirement Levels", RFC 2119, March 1997,
   <ftp://ftp.isi.edu/in-notes/rfc2119.txt>

   [IMAP-LANGUAGE], Gahrns, M., McCown, A., "IMAP4 Language Extension", 
   draft-gahrns-imap-language-00.txt (work in progress), Microsoft, 
   Mitsubishi Electric ITA, November 1997

   [ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
   ABNF", RFC 2234, Internet Mail Consortium, Demon Internet Ltd.,
   November 1997, <ftp://ftp.isi.edu/in-notes/rfc2234.txt>

   [CHARSET-POLICY] Alvestrand, H., "IETF Policy on Character Sets and 
   Languages", RFC 2277, January 1998, <ftp://ftp.isi.edu/in-notes/rfc2277.txt>


8.  Acknowledgments

   This document is derived from [IMAP-LANGUAGE]. The authors would thank 
   Mike Gahrns and Andrew McCown for their perfect work.


9.  Copyright

   Copyright (C) The Internet Society 1999. All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

10. Author's Address

    Alexey Melnikov
    Messaging Direct, Inc.

    Home address :
    121293, Russia, Moscow,
    general Ermolov street, 6 - 90

    Email: alexey.melnikov@messagingdirect.com

    Fax (San Diego, CA) : 1 (619) 8393837

