Help me get SpamAssassin working on FC1, please, I am getting swamped

[Andre Meyer]

Dear Fedora specialists

I have tried to get rid of the mass of spam mails that I receive using
Spamassassin on my FC1 machine. I used this machine as a single user desktop
computer. After going through various manuals* on how to configure
Spamassassin I still cannot get it invoked and no X-Spam headers are
inserted when I look at the mails in Evolution. spamd is running and I can
use spamc manually on test mails. I have switched my MTA to Postfix, because
most manuals suggest using this, added the necessary stuff to the
configuration files and created the spam user (why is this necessary?). What
is missing?

Can anybody explain the process of receiving mail from a POP3 account until
it ends up in Evolution? How can I test the individual processes and check
what goes wrong? Do I need Postfix and/or procmail?

Thanks a lot for your help in advance
Andre

*
http://www.stearns.org/doc/spamassassin-setup.current.html
http://www.securitysage.com/guides/postfix_uce.html
http://www.geekly.com/entries/archives/00000155.htm