valid domain and user

[email protected] Fri, 10 Dec 2004 15:17:17 EST
Newsgroups gmane.mail.spam.active-spam-killer.general
Message-ID <[email protected]>
Is there functionality in ask that I can enable that checks if the user and 
domain of an incoming piece of mail are valid? If not, can I modify the 
.forward file to add this functionality?