SMTP Service Extensions for Transmission of Large and Binary MIME Messages
RFC 3030

Document Type RFC - Proposed Standard (December 2000; Errata)
Obsoletes RFC 1830
Last updated 2013-03-02
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IESG IESG state RFC 3030 (Proposed Standard)
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Network Working Group                                       G. Vaudreuil
Request for Comments: 3030                           Lucent Technologies
Obsolete: 1830                                             December 2000
Category: Standards Track

                        SMTP Service Extensions
                       for Transmission of Large
                        and Binary MIME Messages

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This memo defines two extensions to the SMTP (Simple Mail Transfer
   Protocol) service.  The first extension enables a SMTP client and
   server to negotiate the use of an alternative to the DATA command,
   called "BDAT", for efficiently sending large MIME (Multipurpose
   Internet Mail Extensions) messages.  The second extension takes
   advantage of the BDAT command to permit the negotiated sending of
   MIME messages that employ the binary transfer encoding.  This
   document is intended to update and obsolete RFC 1830.

Working Group Summary

   This protocol is not the product of an IETF working group, however
   the specification resulted from discussions within the ESMTP working
   group.  The resulting protocol documented in RFC 1830 was classified
   as experimental at that time due to questions about the robustness of
   the Binary Content-Transfer-Encoding deployed in then existent MIME
   implementations.  As MIME has matured and other uses of the Binary
   Content-Transfer-Encoding have been deployed, these concerns have
   been allayed.  With this document, Binary ESMTP is expected to become
   standards-track.

Vaudreuil                   Standards Track                     [Page 1]
RFC 3030                      Binary ESMTP                 December 2000

Document Conventions

   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 RFC 2119 [RFC2119].

Table of Contents

   1.   Overview ...................................................  2
   2.   Framework for the Large Message Extensions .................  3
   3.   Framework for the Binary Service Extension .................  5
   4.   Examples ...................................................  8
     4.1  Simple Chunking ..........................................  8
     4.2  Pipelining BINARYMIME ....................................  8
   5.   Security Considerations ....................................  9
   6.   References .................................................  9
   7.   Author's Address ........................................... 10
   8.   Appendix A - Changes from RFC 1830 ......................... 11
   9.   Full Copyright Statement ................................... 12

1. Overview

   The MIME extensions to the Internet message format provides for the
   transmission of many kinds of data that were previously unsupported
   in Internet mail.  Anticipating the need to transport the new media
   more efficiently, the SMTP protocol has been extended to provide
   transport for new message types.  RFC 1652 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 performance-based desire 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 multimedia.  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 that support binary
   message processing.

Vaudreuil                   Standards Track                     [Page 2]
RFC 3030                      Binary ESMTP                 December 2000

   This memo uses the mechanism defined in [ESMTP] to define two
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