You may use Apache SpamAssassin to create a "blacklist" to block unwanted email.
To create blacklists please do the following:
- Login to cPanel and click the SpamAssassin icon.
- If you have not already, please enable SpamAssassin.
- Click the Configure SpamAssassin button.
- Enter any IP address or email address in the blacklist_from field.
- Scroll down and click Save.