I can't see how this could possibly work. If some ".com's" opted to get a ".mail" address for out-going mail, how is that going to address the culprits who will still be using "non-.mail" addresses? I can't see how you could expect every business, organization, or group to use a ".mail" address. The spam will still continue unharnessed.
We need to start focusing on the violators and the source of the problem. All the proposed solutions appear to put the burden on consumers and service providers (eg: filters and sifting), and now on legitimate businesses (.mail).
Can't rules be changed so that headers cannot be falsified? Isn't there some way repeat violators could be civilly and criminally punished. Can't there be a system set up identifying the source and denying the violators further email privileges?
I'm getting tired of walking around with a bullet-proof vest on while the culprits with guns go unmonitored.