want to stop Spam mail - help pls!!!!

We have done some setup for stopping the spam mails, but still we have not been able to stop receiving spam mail onto our server.

Any help would be appreciated.

The current setting that we tried out :
In the configuration document of server -> in Restriction & Controls -> SMTP inbound controls page setup is as follows :

Inbound Relay Controls :
- Allow messages from external internet domains to be sent only to the following internet domains = <oursite.com>
-Deny messages from external internet domains to be sent to the following internet domains = *
- Allow messages only from the following external internet hosts to be sent to external internet domains = <oursite.com>
- Deny messages from the following external internet hosts to be sent to external internet domains = *

In the 'Inbound Connection Controls' section, 'Verify connecting hostname in DNS' is set to 'Disabled'. And 'Deny connections from the following SMTP internet hostnames/IP addresses' is listed to have those websites which we don't want to stop sending spam mails.

Also, in the Notes.ini file, following three variables are set :
SMTPMTA_REJECT_RELAYS=1
SMTP_OCH_Reject_SMTP_Originated_Messages=1
SMTPMTA_Relay_Forwards=1