How To Stop & Prevent “Email Spoofing”?

Question

Currently my server running on Windows 2003 with MERAK(IceWarp) Email Exchange install.

Email Spoofing happen across entire email domain network. How can I stop & prevent email spoofing happen?

Answer 1

On page 44 of the "Anti Spam – Best Practices" IceWarp white paper (PDF):

To make certain that someone cannot breach the system and send messages to server accounts via the server domain name, administrators should select the option, “Reject if originators domain is local and not authorized.” This option prohibits spammers from spoofing legitimate accounts such as PostMaster and Admin, and will eliminate uncertainty in the end user.