On 5 May 1980 the Department of Defense designated the Army as the single manager for the Military Postal Service (MPS). HQ Army established the Military Postal Service Agency (MPSA) as a field operating agency with a Brigadier General as Executive Director with a joint service staff. The MPS is an extension of the United States Postal Service (USPS), and generally operates where the USPS does not. The former Military Mail Terminals of the Army and Fleet Post Offices of the Navy at New York and San Francisco were reorganized in September 1980 as Joint Military Postal Activities (JMPA) Atlantic and Pacific.

The individual services continue to operate their own internal postal facilities, with policy and guidance from the MPSA through their MACOMs. The Interservice Postal School was established in the summer of 1982 at Fort Benjamin Harrison, Indiana under the Soldiers Support Institute (SSI) and moved to Fort Jackson South Carolina in 1995. The school is an Interservice Training Review Organization (ITRO) course hosted by the Army.

The Postal School is staffed by military and civilian instructors from the United States Army, Marine Corps and Air Force. Service Agency (MPSA) as a field operating agency with a Brigadier General as Executive Director with a joint service staff. The MPS is an extension of the United States Postal Service (USPS), and generally operates where the USPS does not.