tar -zxvf Mail-SpamAssassin-2.55.tar.gz
cp spamd/debian-rc-script.sh /etc/init.d/spamassassin You can replace debian by redhat, solaris, netbsd, suse ...
chmod +x /etc/init.d/spamassassin
Then, edit /etc/spamassassin/local.cf
use_pyzor 1 (Only if you have installed pyzor)
use_razor2 (Only if you have installed razor2)
If you want to have detailled information about spamassassin processing, add the line in the local.cf file : timelog_path /var/log/spamassassin, create the directory with appropriate rights (should be vpopmail). In the directory, you will have for each email a file which sum up the spamassassin process (it is a debug option)
In /etc/default/spamassassin (if this file does not exist, create it)
Change ENABLED to 1, then add these options to "-m 10 -v --auto-whitelist".
With that stuff, you can launch spamd which is bascilly a spamassassin deamon (provide great performances).
-m 10 => 10 childs
-v => vpopmail config
--auto-whitelist => Use auto whitelist (friend list)
Instead of spamassassin, you have to use spamc in order to test email.
There are some options "-c -u vpopmail" which enabled the creation of preferences for a domain or a user but it does not work very well for me.