FedEx & UPS challenged by USPS flat rates - Blogging Stocks The United States Postal Service has been heavily promoting it's flat rate deliveries based on the the size of the box instead of the weight in an attempt to retrieve some of the business that it has lost to Federal Express Corp (NYSE: FDX) and United Parcel Service.(NYSE: UPS) over the years. At first glance it would seem the Postal Service is on to something here and might have found a path to increasing its market share taking away some business from its highly successful competitors. But the new flat rate box scheme may turn out to be the governments version of 3-card monte or shell game. The deal is not what it seems.