Vagaries of the US Postal Service

I live in an apartment building, which means that there is a fair amount of turnover, and mail arriving for people who no longer live there.

A few months ago, one such letter arrived. It sat around on top of the mailboxes for a while. Eventually somebody wrote on it, "Moved," but this accomplished nothing.

A few weeks ago, there was a letter in my mailbox, addressed to somebody who must not have lived here for at least three years. Usually I throw mail like that out (neither personal nor important-looking), but this time, on a whim, I wrote "Moved - Return to Sender" on it and stuck it up next to the long-enduring letter.

The next day, my returned piece of mail was gone. Some intelligent person then wrote "Return to Sender" on the older letter. No doubt they confidently believed, as did I, that this would cause the letter to be returned to the sender.

But no! It's still there.