You might want to be careful with this approach; perhaps you could consider validating the emails you received against a list of known "authorized" IP addresses. The danger is that since email is of course sent in plain text, the message could conceivably be sniffed anywhere en route from the sender to the server, including
- the sender's network,
- the router on the sender's network
- the ISP or any machines the message travels through on the public internet
- the router on the receiving end
- the receiving subnet.
Now I'm probably just being paranoid, but one would think that if soemone with malicious intentions sniffed that particular piece of mail, they might realize what it was, and mount a very effective denial of service attack by mailbombing the address. That is, unless you use some form of IP header validation. Also, make sure you keep the email address private. You wouldn't want a random piece of spam to suddenly trigger something important and/or dangerous. ;-)
If you get this working, post some code. It's a cool idea and one that has occurred to me before (although I haven't yet tried it out.)