One thing I’d say is that the PO is stupid when it comes to parcel delivery because they treat it like regular mail and apply those rules. The problems that arise make you not want to use them for parcels.
Specifically, if you move, the PO gives free forwarding service for the first 30 days. After that, you have to pay for it.
But when it comes to things like rental property or temporary living with other family or friends, if you send deliberately send a parcel the old address, you have to use the name of the one living there. If you use yours, the PO will call it undeliverable even if the address is valid. This is fine for regular mail, when you take into account official government correspondence (IRS, DMV, etc.).
But if you know you’re going to get a delivery while out of town and rather it go to a family or friend’s house instead of sitting outside your door for a week, you’ll be out of luck.
Over time, these “undeliverables” have added up making many retailers not want to use the PO for parcels because of the hassle of dealing w/those returns and reorders.
Had a big problem with USPS many years ago. Got a notice in my mail box that I would have to pickup a package at the local P.O. Went to get it, they couldn’t find it & said the one employee who knew where it was would be back in a couple days. Went back & the clown who knew where it was had apparently mailed it back to the sender. It was a package my recently deceased father had coming & I had no idea what it was, or if it was paid for or what. Thanks to one employee. Never did find out anything on it. I was hopping mad over that.