Use USPS to ship to PO Boxes
Shipping to PO Boxes: USPS® is the only carrier that delivers to PO Boxes, so you can use Pirate Ship to purchase postage for shipping to PO Box addresses at the cheapest rates available.
Formatting PO Box addresses: When shipping to a PO Box, no address number or street name is needed in the address. You can format it like this:
Recipient Name
PO Box 12345
City, State ZIP
Big boxes or packages requiring a signature: All packages can be delivered to a PO Box. If the shipment does not fit, or if you purchased a Signature Confirmation service, the Post Office will leave a notice in the box and hold on to the package for pickup.
No time limit for pickup: Once a package is delivered to a PO Box, the recipient has an unlimited amount of time to retrieve it. A Post Office will only return the shipment to you if:
The PO Box is declared vacant with no forwarding address
The package is being held for pickup with notice left in the PO Box, and the recipient does not retrieve it (usually within 30 days)