SMTP Service Extension for 8bit-MIMEtransport
RFC 1426

Document Type RFC - Proposed Standard (February 1993; No errata)
Obsoleted by RFC 1652
Last updated 2013-03-02
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Network Working Group                               J. Klensin, WG Chair
Request for Comments: 1426                     United Nations University
                                                        N. Freed, Editor
                                            Innosoft International, Inc.
                                                                 M. Rose
                                            Dover Beach Consulting, Inc.
                                                            E. Stefferud
                                     Network Management Associates, Inc.
                                                              D. Crocker
                                                       The Branch Office
                                                           February 1993

                         SMTP Service Extension
                         for 8bit-MIMEtransport

Status of this Memo

   This RFC specifies an IAB standards track protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

1.  Abstract

   This memo defines an extension to the SMTP service whereby an SMTP
   content body containing octets outside of the US ASCII octet range
   (hex 00-7F) may be relayed using SMTP.

2.  Introduction

   Although SMTP is widely and robustly deployed, various extensions
   have been requested by parts of the Internet community. In
   particular, a significant portion of the Internet community wishes to
   exchange messages in which the content body consists of a MIME
   message [3] containing arbitrary octet-aligned material. This memo
   uses the mechanism described in [5] to define an extension to the
   SMTP service whereby such contents may be exchanged. Note that this
   extension does NOT eliminate the possibility of an SMTP server
   limiting line length; servers are free to implement this extension
   but nevertheless set a line length limit no lower than 1000 octets.

3.  Framework for the 8bit MIME Transport Extension

   The 8bit MIME transport extension is laid out as follows:

Klensin, Freed, Rose, Stefferud & Crocker                       [Page 1]
RFC 1426                SMTP 8bit-MIMEtransport            February 1993

          (1)  the name of the SMTP service extension defined here is

          (2)  the EHLO keyword value associated with the extension is

          (3)  no parameter is used with the 8BITMIME EHLO keyword;

          (4)  one optional parameter using the keyword BODY is added to
               the MAIL FROM command.  The value associated with this
               parameter is a keyword indicating whether a 7bit message
               (in strict compliance with [1]) or a MIME message (in
               strict compliance with [3]) with arbitrary octet content
               is being sent. The syntax of the value is as follows,
               using the ABNF notation of [2]:

                    body-value ::= "7BIT" / "8BITMIME"

          (5)  no additional SMTP verbs are defined by this extension;

          (6)  the next section specifies how support for the extension
               affects the behavior of a server and client SMTP.

4.  The 8bit-MIMEtransport service extension

   When a client SMTP wishes to submit (using the MAIL command) a
   content body consisting of a MIME message containing arbitrary
   octet-aligned material, it first issues the EHLO command to the
   server SMTP. If the server SMTP responds with code 250 to the EHLO
   command, and the response includes the EHLO keyword value 8BITMIME,
   then the server SMTP is indicating that it supports the extended MAIL
   command and will accept MIME messages containing arbitrary octet-
   aligned material.

   The extended MAIL command is issued by a client SMTP when it wishes
   to transmit a content body consisting of a MIME message containing
   arbitrary octet-aligned material. The syntax for this command is
   identical to the MAIL command in [1], except that a BODY parameter
   must appear after the address.

   The complete syntax of this extended command is defined in [5]. The
   esmtp-keyword is BODY and the syntax for esmtp-value is given by the
   syntax for body-value shown above.

   The value associated with the BODY parameter indicates whether the
   content body which will be passed using the DATA command consists of
   a MIME message containing some arbitrary octet-aligned material

Klensin, Freed, Rose, Stefferud & Crocker                       [Page 2]
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