Thanks for the reponses - I finally figured it out after much trial and error. don't know why it was so hard, but 2 things: had to use GET not POST, and the other part was due to the proprietary software they want to use to send this - had to be fully compliant xhtml.
I have no excuse for doing this other than the recipients are signed up for this email, so it's really between my client and their clients. I've already given them my opinion - i don't know for sure and life is too short to find out - but i think that adding forms to the html email will cause even more isp's to kick it back. they still want to try it.