What can we do to stop spam?

Perhaps just come up with better guides. It took me close to 20 minutes to find any sort of site/page that had a decent explanation of forged email headers/addresses geared toward the non-technical.

e-mail forgery is easy-to-do and not unusual, and, at this point-in-time, little can be done about it

[ MFCF/CSCF Frequently Asked Questions: Dealing with Email Forgery ]

First, props to U Waterloo, I should have just checked the Canadian internets to begin with.

Second, if you are in a position to hire, make sure you hire good IT staff. Don't skimp. Really.

Third, if you are responsible for sending spam, shame on you.