perl-esmtpd is an antispam, antivirus, and
authenticating SMTP daemon. It integrates with
qmail, sendmail, stunnel, etc. It's simple Perl, so
you can hack it to suit your needs. It supports
RBLs, mx on from, bounce evil phrases, virus
scanning, etc. It offers: RBL-sytle black-hole DNS
checking when not relaying, verification of valid MX
records for the MAIL FROM (when not relayin, the
ability to use Stunnel for smtps connections and
still do RBL checks etc., simple authentication (i.e.
PLAIN or LOGIN) for offsite users, and the ability to
reject email with certain key phrases. Many other
useful features are included.
