If you are receiving to many spam email from a particular domain, then you can blacklist that email address OR domain by following these steps:

1. Login to your cPanel hosting account via here.
   
   
2. Open MAILSCANNER
   
3. Open WHITELIST/BLACKLIST Settings
   
4. Enter the spammy email or domain here:
   
5. Don't forget to save by clicking the CHANGE button.