When I forward mail mail from computer A to computer B using the
recipe
:0
! $MY_ADDR
then the mail goes to computer B but the "From " header is rewritten to show
that it came from me at computer A.
:0
* ^From \/[^ ]+[ ]+
| $SENDMAIL -f$MATCH $MY_ADDR
:0
! $MY_ADDR
This says to grab the sender from the From_ header, then invoke sendmail
designating the sender. The second recipe is there to catch messages that
don't match the first one (some sendmail configs will do this).
This first recipe may result in an extra header in your message --
something like "Warning: user 'blah' forced username with -f" (that's
not a direct quote).
Chris