Proposed standard for message header munging
RFC 886

Document Type RFC - Unknown (December 1983; No errata)
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Request For Comments:  886 

             Proposed Standard for Message Header Munging

                       Thu Dec 15 03:37:52 1983

                           Marshall T. Rose

            Department of Information and Computer Science
                   University of California, Irvine
                           Irvine, CA 92717

                         MRose.UCI@Rand-Relay

    This memo proposes a standard for the ARPA Internet community. If
    this proposal is adopted, hosts on the ARPA Internet that do message
    translation would be expected to adopt and implement this standard.



Request For Comments:  886                                       M. Rose
Proposed Standard for Message Header Munging                         UCI

                             Introduction

    This memo describes the rules that are to be used when mail is
    transformed from one standard format to another.  The scope of this
    memo is limited to text messages (computer network mail, or
    electronic mail) that traverse the ARPA Internet.  This memo is not
    presented as a replacement or amendment for the "Standard for the
    Format of ARPA Internet Text Messages", RFC822.  Rather, this memo
    focuses on a particular aspect of mail, and provides a conceptual
    and practical basis for implementors of transport agents and user
    agents which support message munging.

    Although this memo has been specifically prepared for use with the
    822 standard, an understanding of the 822 standard is not required
    to make use of this memo.  The remainder of this section reminds
    the reader of some key concepts presented in the 822 standard, and
    how they relate to the perspective of this memo.

    Messages are viewed as consisting of an envelope and contents.  The
    envelope is manipulated solely by transport agents, and contains
    the information required by the transport agents to deliver the
    message to its recipients.  Although this memo does not address
    itself directly to the envelope, we shall see that some of the
    rules discussed later are applicable to the envelope.

    The contents of the message consists of a rigorously structured
    part, known as the headers, followed by a freely formated part,
    called the body.  The message body is completely uninteresting to
    us.  Our emphasis is strictly on the headers of the message.  Each
    header in the message consists of a field, its value, and a
    terminating end-of-line sequence.  The 822 standard discusses,
    among other things, continuation lines, the syntax that is used to
    distinguish between fields and values, and the syntax and semantics
    of the values of various fields.  For our part, we shall concern
    ourselves only with the notion that the headers section consists of
    one or more headers, which are divided into one or more field/value
    pairs.

    The term "message munging" refers to the actions taken by a
    transport or user agent to transform the contents of a message from
    conformance with one standard format to another.  The 822 standard
    refers to this as "Network-Specific Transformation".  Other phrases
    might be "header munging" or "mail filtering".  Regardless of the
    term used, the key notion is that this action transforms a message
    from its current format (the source message) to the structure
    required by the target standard.  A "munging agent", for the
    purposes of this memo, is an entity which performs message munging.
    A munging agent may be part of either a transport or user agent.

Page 1


Request For Comments:  886                                       M. Rose
Proposed Standard for Message Header Munging                         UCI

                              Background

    As more networks connect into the ARPA Internet community, their
    users will exchange computer mail messages with other Internet
    hosts.  Although the 822 standard must be strictly adhered to for
    mail that traverses the ARPA Internet, other networks might not
    internally adopt this standard.  It is nevertheless desirable to
    permit mail to flow between hosts which internally conform to the
    standard and those which do not.  The 822 standard is very clear to
    indicate that:

         "This standard is NOT intended to dictate the internal formats
         used by sites, the specific message system features that they
         are expected to support, or any of the characteristics of user
         interface programs that create or read messages."

    This plainly states that even hosts within the ARPA Internet, may
    opt to use a different standard than 822 for their internal use,
    but they are expressly required to use the 822 standard when
    transferring mail to other hosts in the ARPA Internet.  As such, it
    is not difficult to imagine message munging becoming a common
    activity among transport and user agents.

    There are other reasons why message munging may become a widespread
    practice.  An example from CSnet will serve here.  The CSnet relays
    provide authorized access for mail services to the ARPA Internet
    for the CSnet phonenet sites.  CSnet sites are not registered with
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