E-Mail Authentification
Email authentication is the effort to equip e-mail with enough verifiable information, so that recipients can recognize the nature of each incoming message automatically. Enabling email authentication will help fight the spread of spam.
Both of the methods below work to prevent forged mail from going in and out of your server. The great benefit of enabling these methods is to prevent mail from looking like it is coming from your domain(s). When enabled, these methods should reduce the amount of bounce messages or unwanted emails received when spammers “spoof” one or more of your email addresses.
Sender Policy Framework (SPF)
SPF will specify which machines are authorized to send email from your domain(s). This means that only mail sent through this sever will appear as valid mail from your domain(s) when the SPF records are checked.
For more information on SPF, please see the Linux Journal Article.
DomainKeys
DomainKeys is a proprietary e-mail authentication system developed by Yahoo! 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.
For more information on DomainKeys, please visit the DomainKeys Project Site.
Both, SPF and DomainKeys can be activated for your domain with a mouse click from within your cPanel.