UPS and FedEx do not, in general, deliver to Post Offices boxes, so Boxify will not provide UPS and FedEx rates when the customer enters a shipping address that contains a recognizable PO box number. Note, however, that FedEx SmartPost and UPS SurePost shipments are available to PO boxes (because USPS handles final delivery), so if you are displaying SmartPost or SurePost rates, Boxify will still provide these rates when a PO box address is entered.