EXACT is a UNIX daemon that provides mail relay control. It is written for those who operate a mailserver and wish to allow mail relaying, conditionally on users authenticating to an IMAP or POP server.
It supports UW-imap, Qpopper, Cyrus, Perdition, TeaPOP, cucipop, EXIM, Postfix and Sendmail out of the box.
This is the current production version: exact-1.41.tar.gz
There is a mailing list, for announcements concerning the software.
Complete documentation is included with the package. You can see the README file for the 1.41 version here: README