Header option files

Some special option files may be associated with a channel that describe how to trim the headers on messages either enqueued to, or  enqueued by, that channel. This facility is completely general and may be applied to any channel; it is controlled by the  ,   ,   ,   ,  , and    channel options.

Various MTA channels have their own channel-level option files as well. Header option files have a different format than other MTA option files and thus a header option file is always a separate file.

Note that the   utility with its    switch can be used to test the effects of header  trimming option files.

As of MS 6.3, note that the Sieve " "  extension provides an alternate way to alter header lines. While header trimming may be a simpler approach for performing simple changes, the  Sieve " " approach is more powerful in  some respects such as allowing changes to specific,  unrecognized-by-the-MTA, header lines, or alterations of the values on  header lines.

See also:
 * headertrim Option
 * innertrim Option
 * headerread Option
 * test -header utility
 * Sieve editheader extension
 * Header option file location
 * Header option file format