DRAC (Dynamic Relay Authorization Control) is a daemon that dynamically
updates a relay authorization map for sendmail. It provides a way to
allow legitimate users to relay mail through an SMTP server, while still
preventing others from using it as a spam relay. User's IP addresses are
added to the map immediately after they have authenticated to the POP or
IMAP server. By default, map entries expire after 30 minutes, but can be
renewed by additional authentication. Periodically checking mail on a
POP server is sufficient to do this. The POP and SMTP servers can be on
different hosts.
From Antoine Jacoutot <ajacoutot@lphp.org>
