Spam Assassin is a great industry standard spam fighting tool, that comes as a free service on most hosting accounts. We recommend to activate it as soon as you create an account or log in for the first time. You only have to enable it once and it will work for all your email accounts.
SpamAssassin scans the contents of each message before it reaches your Inbox, searching for words, phrases and formats common to Spammers. The search then assigns a score, higher being more likely to be Spam and lower being less likely. You choose what score is allowed to enter your Inbox.
How to Enable or Disable Spam Assassin
To enable and disable Spam Assassin please do the following:
Login to cPanel and look in the Mail section
Click Spam Assassin™
Click Enable SpamAssassin to enable
Click Disable SpamAssassin to disable
You have now just enabled / disabled Spam Assassin.