Shipping a package to a PO Box looks easy—until UPS/FedEx reject it, labels fail, and you eat the refund. This practical guide explains what you can ship to a U.S. PO Box, when to use USPS, and how to set Shopify rules plus Ultimate PO Box Blocker so bad addresses never pass checkout.

Most Shopify shipping issues start with bad data: missing dimensions, mis-matched zones, or PO-Boxes that private carriers can’t reach. Learn a five-step workflow to audit rates, validate addresses, and automate fixes—then add Ultimate PO Box Blocker to catch U.S. PO-Boxes at checkout so every label prints cleanly.

A sloppy FedEx integration with Shopify burns profit and ruins delivery promises. This 2 000-word playbook shows you how to connect carrier-calculated rates, map zones, automate labels, and block undeliverable PO-Boxes before checkout. One toggle—Ultimate PO Box Blocker—guarantees every address is FedEx-ready.