>"the USPS has a detailed process for formally putting a company on notice for mailing someone who has specifically unsubscribed, and that process ends in massive fines for continued mailing to that person."

I am doubting this is enforced in any meaningful way. I don't doubt there is a well-detailed process however the US Post Office's bread and butters seems to be Dell Catalogs and Southwest Airlines credit card offers. This fact is what killed Outbox:

http://www.insidesources.com/outbox-vs-usps-how-the-post-off...