This package is based on the package 'postgrey' from project 'server:mail'.

Postgrey is a Postfix policy server implementing greylisting.
When a request for delivery of a mail is received by Postfix
via SMTP, the triplet CLIENT_IP / SENDER / RECIPIENT is built.
If it is the first time that this triplet is seen, or if the
triplet was first seen less than 5 minutes, then the mail gets
rejected with a temporary error. Hopefully spammers or viruses
will not try again later, as it is however required per RFC.

The following features compared with greylist.pl from Postfix 2.1.1
are new:
Safe database, automatic maintenance, whitelists, lookup by subnet,
auto-whitelisting of clients, only Berkeley DB and no large mysql
nor postgresql DB needed.