The Batch SMTP Media Type
RFC 2442

Document Type RFC - Informational (November 1998; No errata)
Was draft-freed-bsmtp (individual)
Last updated 2013-03-02
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Network Working Group                                         N. Freed
Request for Comments: 2442                                   D. Newman
Category: Informational                                       Innosoft
                                                          J. Belissent
                                                      Sun Microsystems
                                                                M. Hoy
                                                         November 1998

                               Batch SMTP
                               Media Type

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.


   This document defines a MIME content type suitable for tunneling an
   ESMTP [RFC-821, RFC-1869] transaction through any MIME-capable
   transport.  This type can be used for a variety of purposes,
   including:  Extending end-to-end MIME-based security services (e.g.,
   [RFC-1847]) to cover message envelope information as well as message
   content.  Making it possible to use specific SMTP extensions such as
   NOTARY [RFC-1891] over unextended SMTP transport infrastructure.
   Enabling the transfer of multiple separate messages in a single
   transactional unit.

Requirements Notation

   This document occasionally uses terms that appear in capital letters.
   When the terms "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
   appear capitalized, they are being used to indicate particular
   requirements of this specification. A discussion of the meanings of
   the terms "MUST", "SHOULD", and "MAY" appears in [RFC-1123]; the
   terms "MUST NOT" and "SHOULD NOT" are logical extensions of this

Freed, et. al.               Informational                      [Page 1]
RFC 2442                 Batch SMTP Media Type             November 1998

The Application/batch-SMTP Content Type

   The "application/batch-SMTP" MIME content type is a container for the
   client side of an SMTP or ESMTP transaction. In keeping with
   traditional SMTP, the contents are line oriented and CRLF line
   terminators MUST be used.

   The "application/batch-SMTP" type is defined as follows:

      Media type name: application
      Media subtype name: batch-SMTP
      Required parameters: none
      Optional parameters: required-extensions
      Encoding considerations:
        8bit material may appear, so quoted-printable or base64
        encoding may be necessary on transports that do not
        support 8bit. While the content of this type is
        line-oriented and uses conventional CR/LF terminators,
        lines longer than 7bit and 8bit encodings allow (998
        octets) may appear, hence quoted-printable or
        base64 encoding may be necessary even in conjunction
        with 8bit transports.
      Security considerations:
        Discussed in the Security Considerations Section.

How application/batch-SMTP is used

   The following diagram illustrates how the application/batch-SMTP type
   is intended to be used:

                    application/batch-SMTP object
                         |                |
           +-----------+ v  +----------+  v +-----------+
           | batch     |    | MIME-    |    | batch     |
        => | SMTP      | => | capable  | => | SMTP      | =>
           | generator |    |transport |    | processor |
        ^  +-----------+    +----------+    +-----------+  ^
        |                                                  |
        +-- conventional SMTP/RFC822 message transaction --+

   A conventional SMTP message transaction is converted into an
   application/batch-SMTP object by the batch SMTP generator. This
   object is then carried over some type of MIME-capable transport. Once
   the destination is reached the object is presented to a batch SMTP
   processor, which converts the application/batch-SMTP object back into
   a conventional SMTP message transaction.

Freed, et. al.               Informational                      [Page 2]
RFC 2442                 Batch SMTP Media Type             November 1998

Generation of application/batch-SMTP material

   Application/batch-SMTP material is generated by a specially modified
   SMTP client operating without a corresponding SMTP server. The client
   simply assumes a successful response to all commands it issues. The
   resulting content then consists of the collected output from the SMTP

Honoring SMTP restrictions

   Most batch SMTP processors will be constructed by modifying and
   extending existing SMTP servers. As such, all of the restrictions on
   SMTP constructs imposed by RFC 821, RFC 1123, and RFC 1869 MUST be
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