HI , can some one please help me with spam control ?

I have a lot of Spam and I donít know what more can I do , I set up the RBL with this options :

zimbraMtaRestriction: check_client_access hash:access
zimbraMtaRestriction: reject_invalid_hostname
zimbraMtaRestriction: reject_non-fqdn_hostname
zimbraMtaRestriction: reject_non_fqdn_sender
zimbraMtaRestriction: reject_rbl_client dnsbl.njabl.org
zimbraMtaRestriction: reject_rbl_client opm.blitzed.org
zimbraMtaRestriction: reject_rbl_client relays.ordb.org
zimbraMtaRestriction: reject_rbl_client cbl.abuseat.org
zimbraMtaRestriction: reject_rbl_client bl.spamcop.net
zimbraMtaRestriction: reject_rbl_client dnsbl.sorbs.net


but still im getting a lot of spam .

Before I was dealing with the simple configuration of Spam assassin and with just putting up the score it was good , now I donít know where I can change that to improve the system or what else I can do to stop Spam .

thanks in advance.