Spam Solution - Checkback on Subject

One of the problems with spam is that you do not have verification that the sending mail server is who it claims to be. One way of countering this is to receive the mail, then call back to the claimed sending mail server to verify that they actually sent the messages.

Since verifying the entire message amounts to resending the entire message, it should be possible to simply extend the mail servers to allow one to call another and verify by asking about the sending address, the receiving address, and some small digest representing the message. A typical way of calculating this digest could be a hash of the actual subject line.

This page maintained by Rob (at ewan dot com, of course).