third party relays put us on spam lists, How do I stop relays

[yourkeylady]

Hi everyone,

I have a website that uses sendmail, I don't know what version yet. I heard that I need to block the smtp port for outgoing mail to stop 3rd party spammers. I am on a shared server and have to access to the config file.

The control panel version is cPanel 0.9.9.2 (RC8)
Under it's mail options it has spam assasin and Box trapper spam trap. But I think these porgrams are only for incoming mail.

What should I do to keep spammers from sending mail with my websites name

Thanks
Tricia