Got turned on to an IETF draft standard that, hopefully, will not only eliminate some spoofed e-mail traffic on the web, but allow our outgoing mail to be accepted more readily.
The draft is entitled "Sender Policy Framework", and allows mail servers a way to check whether or not incoming e-mail originated from the server(s) authorized to send mail for that domain.
It's pretty simple to do with your DNS registrar...if it helps, I can't see a downside to doing it. Those with nothing to hide, hide nothing - right?
By the way, I've never mentioned it, but Postini is godsend to anyone who handles internet e-mail. There are folks who argue that appliances & software in their data center is the way to go - these people must have more money and bandwidth than they need.
Do the math - outsource it!