914,
An email message doesn't retain the IP address of the router's that it was routed through - only the MTAs. There is no guarantee of this since any MTA can strip those headers (that's how remailers work).

While this would work in a script that gets the IP before sending the email- it adds several new security concerns. What happens if nathanvit forgets to shut off the cronjob before going on vacation. He isn't around to monitor his email and his mailbox fills up - where does the undeliverable go?

This is just plain bad juju - I don't like this one bit, I do not like it Sam I am.

L~R