Antispam on OSX Server 10.3.3

Hey,
which is the best server-side solution you would suggest me in order to reduce the amount of spam received?

I followed the article on clamav and amavisd and I could configure clamav but not spamassassin to work with the file versions present in the article.
I tried to install the newest release of the files and I got a message telling me a library is missing.

Unfortunately I’m not in front of the server in order to tell tÏyou the exact error message.

Thanks in advance for your help.

M.