> Although I am reluctant to suggest > anything involving public key crypto, another approach would be to put a > public key in the MAIL-FROM DNS record and add a new header field containing a > signature covering the message's MAIL FROM and the current date. that's an interesting idea. I don't see a big problem with doing something like this as long as you don't try to make it a signature for the message - it's just a way to say "I can prove that I have the right to use this MAIL FROM". you might need to include more than just the date though. Keith