The sample header lines in DSNs: the return header.opt file

The sample header lines in DSNs: the  file
The purpose of the  file is to specify  which message header lines to include to identify a message in the  human-readable first part of DSNs. Typically it is desired to return only a few of the possible header lines a message might contain, only  those most significant to the original message sender.

Prior to MS 7.0 update 2, the  file was  not language-specific: it always resided and was found in the  IMTA_LANG: directory. All the other  files may  be language-specific, as the directory in which to locate them may be  varied using the     mapping table. As of MS 7.0 update 2, the MTA will first look for a language-specific   in  the directory (or as of MS 7.0 update 3, list of directories) selected  via   in the   or    mapping  table, as relevant; but if the MTA does not find a language-specific  such file, then it will fall back to looking in the LANGDIR directory  instead. (As of MS 7.0, the former IMTA_LANG Tailor file option is deprecated and replaced by the    MTA option as far as locating on  disk where files are located. But IMTA_LANG may still be used in, for  instance, mapping tables: the MTA will translate occurrences of  IMTA_LANG to the location specified by the   MTA option.)

As a concrete example, the  file  installed in the IMTA_LANG: directory is shown here. The settings shown  here mean that the    substitution typically used in the     file  will cause insertion of solely the Message-Id:, Date:, From:, To:, and  Subject: header lines of the original message into the first,  human-readable portion of the DSN messages constructed by the MTA; all  other header lines from the original message will be omitted. See the    utility for an example of application of this header  trimming to a set of headers. (Note that the  MTA option controls any decoding and/or character set conversion of any MIME encoded non-US-ASCII  material in such substituted header lines.)

 Sample distributed  file

Message-Id: PRECEDENCE=3 Date: PRECEDENCE=4 From: PRECEDENCE=5 To: PRECEDENCE=6 Subject: PRECEDENCE=7 Others: MAXIMUM=-1 Defaults: MAXIMUM=-1

See also:
 * langdir MTA Option
 * NOTIFICATION_LANGUAGE mapping table
 * The required full set of DSN type-specific return_...txt files
 * test -header utility
 * notary_decode MTA Option
 * Customizing DSNs via the return files