[marylina]

Does the PO send this refused piece of ($*#!) mail back to the sender, or does it just discard it?

[marylina]

Answering own question: probably by law, the PO has to send the letter back to the sender.

[GretchenEE]

My understanding is they send it back if it has a guaranteed return. The PO and the sender benefit because it's a message to the sender that you want off their mailing list, and the PO has the happy prospect of fewer junk mails to deliver. Sometimes it actually works, especially for organizations that try to keep costs down.