Postpals is a simple policy daemon for Postfix. It keeps a database of
outgoing mail, specifically recipients and relays associated to them.
The main goal is to whitelist mail coming back from those senders and
relays early in the postfix restriction chain, so it doesn't get hit
with any client UCE checks you are using (RBL, helo, PTR, greylisting etc).
Submitted by: Sahil Tandon <sahil at tandon.net>