I have created a very detailed HOWTO document on building an
anti-spam mail relay server.  I had need of this because my
company uses MS Exchange server internally, and we have
anti-virus software on it, but needed a way to control spam.  We
decided to build a server between the Exchange server and the
firewall, the sole purpose of which was to filter out spam on
inbound mail. This HOWTO is the result.  It is written such that
an almost newbie (like myself) could build it.  This system was
built on Red Hat 7.3 and does not scan for viruses, but these
things could of course easily be changed by those who wanted a
slightly different setup.  I have tested this configuration on 2
machines and will be installing on our production model probably
within a month.  I plan to continue to improve the document, and
would be very happy for any suggestions from anyone interested.

Scott Henderson

SPAMFILTER HOWTO:
http://www.cyberspace.org/~boyhowdy/spamfilter.html