But of course you’d probably have to find some way to pay for the extra sorting. Or require that all senders provide a machine-readable return address label. Either way, I think the way to pitch this to the USPS is as a new feature they can provide: mail filtering. Then maybe they could provide you with the ability to provide an arbitrary set of rules (code) for selecting what is delivered to you. It it really gets to be like email, you’ll be seeing mail stamped with X-Spam-Status on it.