My only address associated with the USPS is my PO box and not my physical address.
Local Post Office has many lockers for packages that won't fit in actual P O Box. If package is too big for the lockers they leave a notification card in my PO box. All the local mail goes thru another town's Post Office & since my physical address is not in the USPS system the other town's PO will return it. The E-bay computerized address system will not accept my PO Box number even as an option address. If it would that would be very helpful because when they see the PO box number they send it thru to my local Post Office. When I try to add my PO box number the system replies with message indicating that seller does not ship to PO boxes. What is very frustrating is that often the item is very small & would easily fit in the standard PO box. In these situations does the seller not ship the item? It's difficult to believe that there isn't millions of people that the only address the USPS has in their system is a PO box.
In our area they combined the two town's Post Offices and did not eliminate one of them to improve efficiency. Unfortunately this hybrid PO system probably isn't very common.