amavisd-new is an interface between message transfer agent (MTA) and
one or more content checkers, e.g. virus scanners, SpamAssassin, etc.
It is a performance-enhanced and feature-enriched version of amavisd
(which in turn is a daemonized version of AMaViS or amavis-perl).

amavisd-new is normally positioned at or near a central mailer, not
necessarily where user's mailboxes and final delivery takes place.  If
you are looking for fully per-user configurable and/or low-message-rate
solution to be placed at the final stage of mail delivery (e.g. called
from procmail), there may be other solutions more appropriate for your
needs.

Homepage:
https://www.amavis.org/
