net-mail
policyd-weight is a Perl policy daemon for the Postfix MTA (2.1 and
later) intended to eliminate forged envelope senders and HELOs (i.e. in
bogus mails). It allows you to score DNSBLs (RBL/RHSBL), HELO, MAIL
FROM and client IP addresses before any queuing is done. It allows you
to REJECT messages which have a score higher than allowed, providing
improved blocking of spam and virus mails. policyd-weight caches the
most frequent client/sender combinations (SPAM as well as HAM) to reduce
the number of DNS queries.