EXACT is a program that implements POP-before-SMTP
relay authentication. It supports UW-imap,
Qpopper, Cyrus, Perdition, TeaPOP, EXIM, and
Sendmail out of the box. POP-before-SMTP relay
authentication is commonly used on systems that
provide IMAP and/or POP services as well as SMTP
services, to authenticate users for mail sending
based on their previous authentication against an
IMAP or POP server.
