Summary: For more than 200 years, the U.S. Postal Service and its predecessors have enjoyed a statutorily imposed monopoly restricting the private delivery of letters. The monopoly was intended to enable the postal system to fulfill its mandate of providing uniform rates for at least one class of letter mail and delivery of letter mail to patrons in all areas, however remote. Some large mailers and private carriers want Congress and the Postal Service to allow greater competition for letter mail delivery. Others have raised concerns about how increased private delivery might affect the Postal Service's ability to sustain mail services traditionally provided by the government, especially since the Postal Service now receives virtually no federal money. This volume: (1) determines the historical and current basis for restricting private delivery of letters, including the Postal Service's efforts to enforce those restrictions; (2) documents changes in private sector letter delivery capacity since 1970; (3) analyzes the possible financial effects on the Postal Service's revenues, costs, and postal rates if restrictions on private letter delivery were to be changed; and (4) provides information on how recently reformed postal administrations abroad provide universal service and restrict private letter delivery. The second volume (GAO/GGD-96-129B) presents a detailed analysis of the restrictions in federal, civil, and criminal law on private letter delivery.