Well you may think that's a good idea but is child's play to change your MAC address and all other types of Tom Foolery for the real SPAMMER - which now days is a bit more dedicated than in the past.
Currently there is no fool-proof method as you can not force others to use what you're using. Digital certs would be a good step but again with thousands of mail providers it isn't going to happen in my opinion.
Someday something will happen, but don't think it will be any time soon.
