Reply from the Postmaster
I actually received a letter back from the Postmaster today, pretty much confirming what I thought. They said that they have to deliver all mail with a correct address and postage, and suggested I write the people sending me mail to tell them to stop mailing me. I’ve done this quite a bit, but it’s a pain to mail everybody, and it doesn’t stop saturation mailings (where a place pays the post office to just stick a copy in everybody’s box, and the address is just “Postal Customer” so they can’t just not print an address label for me). They also reminded me that I can refuse mail being sent to me by marking it Refused and putting it back (which is what I’ve been doing all along, and no doubt the Postmaster knows it).