Just as a note, QMail is a really speedy and robust server that has the advantage over sendmail, the "traditional" mail exchanger, of being more modular. This makes it easy to insert or replace parts of QMail with Perl.

Since you can pick and choose what you want to replace, it is fairly easy to get going and add features. Admittedly, learning QMail is not super simple, but it is far easier than Sendmail or any of the contemporaries. A good book would certainly help get you on your way, and there is a mailing list which can come in very handy.