Amazon Sunday Packages Won’t Stem Postal Losses - Bloomberg Amazon.com Inc. (AMZN)’s new deal with the U.S. Postal Service will put diapers and books into the hands of its customers on Sundays. Postal Service officials want it to pave the way for similar deals in the future. While the Amazon arrangement will offer a limited financial boost, Postmaster General Patrick Donahoe said in an interview that he wants to expand the service to other retailers. Amazon doesn’t have an exclusive deal for Sunday delivery. Weekend and custom deliveries are nothing new for the Postal Service, which trails FedEx Corp. (FDX) and United Parcel Service Inc. (UPS) in express delivery. UPS has 51 percent of the U.S. small-package shipping market, followed by 34 percent for FedEx and 15 percent for the Postal Service, according to a Bloomberg Industries report.