Bluehost offers a whole set of things that you can do to reduce spam. Here is what you do:
- Logon to yourdomain.com/cpanel
- Goto the mail section and enable Spam Assassin
- Then enable Spam Box
- Now create a folder called Spam in your email folders so that Spam Box can put Spam Assassin mail there
- Turn on Spam Hammer which basically rejects the first mail sent from places it doesn't recognize as most mailers will retry but not spammers
