Hello!
maybe anyone can write small, modern howto about topic?
I use sendmail with greylisting, who help a lot. i also use spamassassin, and milter-regex, who is also good tool, especially for turn off situation, when you got spams from faked your own addresses. i also use procmail to send to /dev/null messages with spamassassin score higher than 7.
some days ago one people says me, a SPF tool also is very good to spam fighting - i search around a bit, but not get fresh statistics
( last seems to be of 2009 ?http://www.openspf.org/Statistics )
as so i want to know - it is worth to turn it on, or not? looks like for it work i must add SPF records to DNS, and add spf milter to sendmail, at least....?

I am not good at writing how-to yet for slackware but i can point you to some web stuff to take a look at....

http://littlesvr.ca/linux-stuff/arti...-filtering.php

http://dctrl.fi-b.unam.mx/victor/des...amAssassin.pdf

This one looks nice too its been updated this year http://notes.sagredo.eu/node/37


Hope those help...