I suffer from the same problem. We have no mail delivery in the town I live in so I have had a PO box since I moved here.
It's extremely difficult for me to order things online because a lot of sites say they use USPS so I try and enter my PO box and I get pop ups saying UPS doesn't deliver to PO boxes. So I enter my street address and they end up shipping USPS and because my PO box isn't on there it gets sent back.
And around and around we go. :banghead:
I have explained this to the local PO on numerous occasions and it's like they don't understand.