I created this Perl program by borrowing code from Matt's Formmail.

Just on this one point - you may well be unaware of the poor security reputation of that particular script. See for example the CVE entries for it. Please be very, very careful if you are deploying this script or one based upon it to a public-facing web server.

If you must use something based upon this script (and really you shouldn't have to) consider the NMS rewritten version instead.