 FedEx and United Parcel Service (UPS) directly compete with USPS Express Mail and package delivery services, making nationwide deliveries of urgent letters and packages.Due to the postal monopoly, they are not allowed to deliver non-urgent letters and may not directly ship to U.S. Mail boxes at residential and commercial destinations.However, both companies have transit agreements with the USPS in which an item can be dropped off with either FedEx or UPS who will then provide shipment up to the destination post office serving the intended recipient where it will be transferred for delivery to the U.S. Mail destination, including Post Office Box destinations.