The main reason that USPS won’t allow UPS or FedEx to deliver to PO boxes is because they want to keep their business for parcels — not letters. That’s because larger packages are what they do best and that is their primary business. They also don’t want to pay the postage needed to ship to PO boxes.
However, some couriers do have loopholes that let them ship to PO boxes. These are services like UPS SurePost and FedEx SmartPost. They are hybrid services that take the package most of the way and then hand it over to USPS for the final delivery. The problem is that not many people know about these services or how to use them.
Another workaround is for customers to sign up for a PO box street address with USPS. This program lets them link their physical street address to their PO box number and then use that as a shipping address when online shopping with merchants who don’t accept PO boxes. This is not a foolproof solution because you still have to trust the carrier to deliver to the correct location.
The best way to ensure that you aren’t missing out on sales is by ensuring that your mailing list contains only valid and verified addresses. That means double-checking the addresses, formatting them correctly and using tracking options when possible. This will help you avoid losing money on shipments to PO box addresses.