Spam Filtering - Postfix, Amavis, Spam Assassin

[Tekati]

How is it that Outlook can do a great job at filtering spam but ISPConfig3 with Postfix, amavis and spam assassin can't catch the same stuff. I even set spam down to level 1 and kill at level 3 and have it mark spam with **** SPAM *** in the subject and I still get a ton of spam through that is not marked. Is there some custom settings I can put into place to help combat spam? The crazy thing is Outlook still does a great job at putting spam in the spam folder most of it is not marked *** SPAM *** in the subject though

[till]

There are a lot of additional extensions and rulesets available.

http://wiki.apache.org/spamassassin/CustomPlugins
http://wiki.apache.org/spamassassin/CustomRulesets

my defult ispconfig installation filters > 95% of the spam without any false positives. So if your system is less accurate in filtering, you might want to check the headers of the mails that had come trough to see which rules applied to them.