October 1, 2013 By Jonathan Ping 31 Comments. […] with Street Addressing, a customer’s mailing address may be either the street address for the Post Office where their PO Box is located, followed by # and the box number, or PO Box followed by the box number. Some merchants do not allow shipping to a PO Box address.y business (LLC) is in Maryland and I switched from a UPS box costing $300+ per year to a USPS box costing $80 per year. I had to go to a couple different post offices before finding the one that new what I was talking about regarding a street addressing format for my box (rather than PO Box address format).