Using Qpsmtpd (O'ReillyNet)
O'ReillyNet has a review
of Qpsmtpd. "
Those who administer an email server more than likely have put up with the pain of adding dnsbl lookups to something like Sendmail or Qmail, or adding recipient validation for their custom user database in Postfix. Extending email servers is painful, and for the most part you can't do it easily in Perl. Wouldn't it be nice if you could do something like mod_perl in a mail server?