The building I work in has a mail chute which empties into a standard USPS collection box. I’ve always used it, but wonder about the possibility of letters getting stuck. Does the post office ever look in them to check for “stuck mail?”
I dunno, but I remember, in one of the Eloise books, little Eloise saying she was going to pour a pitcher of water down the mail chute at the Plaza. The kid had style.
I don’t know the answer either, although I’ve always been told not to use a mail chute for important mail. Here’s my favorite story about mail gone astray from a mail slot.
The building I used to work in had glass-fronted mail chutes, so you could see if anything was stuck in them. The USPS folks didn’t routinely check, but we’d just stick a note on the collection bin in the basement (“letter stuck in chute on 9th floor”), and they’d come unlock the chute and clear it.
If the chute’s opaque, a stuck letter would, I’d guess, eventually cause a noticeable backup, but maybe not. Could be risky for something like your mortgage payment or tax return!