Earlier quoted context omitted.
AFAICT, mail forwarding is done by the local post office that would have delivered the mail. So mail headed to CA gets to your local CA post office, gets a yellow sticker on it, and gets stuck back in the mail. Mail originating in MA, destined for a CA, and forwarded to MA, does indeed cross the country twice. And routing loops loop , true story. How do they submit forwarding updates to remote post offices? Well, the…
I thought mail forwarding was done at the initial address scan, not the final address scan. I did a bunch of research on this a few months ago, but unfortunately I can't find a source right now.
That would make the most sense, but I've observed contradictory behavior with MA->CA->MA mail taking ~10 days. Also, the CA post office not respecting the "end forward" date, and mail getting sent back and forth a few times. I suppose I could have been seeing corner cases due to some unknown facet, but to me they indicate an antiquated system.