[ Thanks to calum.org for this link.
“Like everyone, spam (or UCE–unsolicited commercial email) is
the bane of my life.
“If you run your own Postfix SMTP server however, there are lots
of things you can do to stop it. This is a little crib sheet of
what I do on most of my servers (as much for my ease-of-access as
for other people)…”