Portions of it have been privatized for well over 100 years.
Railroads moved mail for over 100 years.
Airmail was almost entirely handled by private contractors.
Commercial airliners were used to move mail.
FedEx is USPS's largest air package contractor.
USPS uses many ground contractors ranging from giant trucking firm like J.B. Hunt to local contractors who bid on mail post office routes.
Rural mail carriers use their own vehicles. For many years a local postmaster ran the local post office out of part of their home as the town only had 150 people.
Nearly 2,800 post offices operating in local stores and other locations.
When postal services first reaches a new areas of the frontier the post office would often contract with a local stage coach stop, store or similar location as post office until the population warranted a official building.
Originally mail was only delivered from post office to post office. You could interject a little private enterprise into the matter is your home was located on a postal road by bribing the carrier to drop your mail off at your home on their regular route.
One of the oldest forms of private enterprise was the bribing of government officials to grant local postmaster appointments.
