cPanel 11
 
Enable RBL Enable Greylisting
If this option is enabled, the server rejects mail coming from known sources of spam according to published blacklists that are constantly updated. We recommend enabling RBL to reduce spam. If this option is enabled, the server delays accepting mail from unrecognized sources. Many spam servers only make one attempt to deliver a message. We recommend enabling Greylisting to reduce spam.
SpamAssassin

The anti-spam gateways use SpamAssassin to assign a score to each email message. A high score means that the message is almost certainly spam. You can choose to reject mail or modify the subject line of the mail, based on the spam score. To receive tagged mail, your chosen tag score must be less than your reject score. Additional details are added to the complete headers of the email message.

Tag mail if spam score exceeds:
(Default value: 7) 		Reject mail if spam score exceeds:
(Default value: 12)
With this option enabled, the server adds the word *SPAM* to the subject line of suspect email. Choose a low number to get an idea how the server scores spam. With this option enabled, the server rejects spam during the SMTP dialog. (The sender's SMTP server will generate a bounce message depending on its own configuration.)
Whitelist
Always accept mail from:		 Blacklist
Always reject mail from:
Whitelist and blacklist may contain email addresses, domains, and/or IP addresses. Use line breaks to separate the entries. (Email addresses and domains are based on the Return-path of each message, which may differ from the From address.)

Please allow up to one hour for your changes to take effect.