Assuming the USPS and physical addresses are in the same town, the following format can work quite well: 314 Something Rd / PO 404 Town, City 12345 This work

Assuming the USPS and physical addresses are in the same town, the following format can work quite well: 314 Something Rd / PO 404 Town, City 12345 This works because the postal service tries to deliver to the last thing on the label that they recognize. Using slash as a separator works better than a comma or newline because it's less likely the service you're shipping from will "notice" that you put a PO box in and force the package to send via USPS.