Stop Spamming using SpamAssassin SPF Records and Domain Keys:

SpamAssassin is a great resource for fighting and blocking spam to any email account that you have set up with your cPanel server. SpamAssassin is an open source email filtering system designed to identify Spam using many different ways.

SpamAssassin is not an email filter, as some other spam preventin tools are. Instead, it determines whether an email is spam as soon as it hits the server. SpamAssassin works on the back end of your email server and has 10 different levels of settings to catch spam. When enabled by default, you will be set to 5.

Enabling SpamAssassin:

You can enable and configure spamassasin to identify and prevent spam. For that please see the following link: How to enable SpamAssassin and configure it

Domain Keys
Domain Keys is an e-mail authentication system that allows for incoming mail to be checked against the server it was sent from to verify that the mail has not been modified. This ensures that messages are actually coming from the listed sender and allows abusive messages to be tracked with more ease.

SPF
SPF will specify which machines are authorized to send email from your domain(s). This means that only mail sent through this server will appear as valid mail from your domain(s) when the SPF records are checked.

Both the SPF Records and Domain Keys can be set within the “Email Authentication” section of your cPanel.