PMDF DECODE and ENCODE have been, for the most part, made
    obsolete by PMDF MAIL. If you use PMDF MAIL, then files which
    you send with the SEND command will be encoded automatically,
    if necessary. Encoded messages which you receive will be decoded
    automatically, if necessary, and can simply be extracted to a
    file with the EXTRACT command. If, however, you do not use PMDF
    MAIL, then read on.

    The ENCODE and DECODE utilities are provided with PMDF as a means
    of transmitting OpenVMS binary files via MAIL. With ENCODE,
    a file can be encoded in a format which uses short records
    containing only printable characters. Such files can then be
    transmitted through most any mail system without being altered
    (e.g., lines wrapped, characters removed or replaced, etc.).
    ENCODE preserves all file contents and all file attributes
    when encoding a file. The contents and attributes are properly
    restored when decoded with DECODE. Absolutely any type of OpenVMS
    file can be transmitted with these two utilities - even indexed
    files with multiple keys and files with extended semantics such
    as DDIF files.

    Encoded files have two parts. The first part is a conventional
    RFC 822 message header. Header lines are used to describe the
    file format; this information includes a conventional OpenVMS
    FDL (file description language) description of the file and
    a description of the encoding used to convert the file into a
    printable form for transfer. ENCODE creates this header; DECODE
    reads it and uses the information it contains to reconstruct the
    file.

                                   NOTE

       Many encoded messages received with PMDF are automatically
       decoded for you, thus obviating the need to use PMDF DECODE
       at all. This is especially true when you use PMDF MAIL whose
       EXTRACT command will extract any MIME encoded message or
       message body part. If you use VMS MAIL, however, you can
       occasionally receive an encoded message which PMDF could not
       deliver in its decoded form to VMS MAIL owing to limitations
       of VMS MAIL itself.