I read a really nice article by Mike Rubel supporting the use of RMX records to help prevent the spoofing of the FROM: header.

This document supports and encourages the adoption of Hadmut Danisch's RMX resource records for DNS. RMX records are intended to make email forgery difficult by providing a mechanism for a domain owner to list all mail servers authorized to send email on behalf of his or her domain name. They eliminate the most serious drawback of SMTP--the meaningless From: header--without breaking any core internet protocols.

The RFC is a little dry to read so stick with Mike's article.

Chris