RFC 1830 (rfc1830) - Page 1 of 8

SMTP Service Extensions for Transmission of Large and Binary MIME Messages

Network Working Group                                       G. Vaudreuil
Request for Comments: 1830                        Octel Network Services
Category: Experimental                                       August 1995


                        SMTP Service Extensions
                       for Transmission of Large
                        and Binary MIME Messages

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  This memo does not specify an Internet standard of any
   kind.  Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

1. Abstract

   This memo defines two extensions to the SMTP service.  The first
   service enables a SMTP client and server to negotiate the use of an
   alternate DATA command "BDAT" for efficiently sending large MIME
   messages.  The second extension takes advantage of the BDAT command
   to permit the negotiated sending of unencoded binary data.

2. Introduction

   The MIME extensions to the Internet message protocol provides for the
   transmission of many kinds of data which were previously unsupported
   in Internet mail.  Anticipating the need to more efficiently
   transport the new media made possible with MIME, the SMTP protocol
   has been extended to provide transport for new message types.  RFC
   1426 defines one such extension for the transmission of unencoded 8
   bit MIME messages [8BIT].  This service extension permits the
   receiver SMTP to declare support for 8 bit body parts and the sender
   to request 8 bit transmission of a particular message.

   One expected result of the use of MIME is that the Internet mail
   system will be expected to carry very large mail messages.  In such
   transactions, there is a need to eliminate the requirement that the
   message be scanned for "CR LF . CR LF" sequences upon sending and
   receiving to detect the end of message.

   Independent of the need to send large messages, Internet mail is
   increasingly multi-media there is a need to avoid the overhead of
   base64 and quoted-printable encoding of binary objects sent using the
   MIME message format over SMTP between hosts which support binary
   message processing.




Vaudreuil                     Experimental