SpamAssassin

I am running Mandrake Linux 9.2 (sbmldap) as a Mail Server (Postfix) on a entire site. SpamAssassin has been activated. Most of the mails which we receive has a subject line: ***SPAM***. Please advice me how to disable/cancel SpamAssassin or how to clear the ***SPAM*** subject line. I have done some searching on the “Net”, no luck. I am really out of ideas. Please advice