I’m surprised the USPS didn’t develop a hosting service and server farms of its own to help bring in income...since electronic communications could be seen as an evolutionary step from paper mail service, it would help the USPS become relevant, profitable, and yet still serve its constitutional niche.
Constitutionally, it would take an amendment to do away with the postal service. Congress could try to close it but the closure would be challenged in court and the courts would say to congress...”you must fund a viable post office or pass an amendment that 3/4th’s of the states must ratify”. The vagaries of the business world could put private mail firms out of business or make it too expensive to send some of the few paper documents that must needs be sent by mail(registered or otherwise).
An organized vigorous country must always need a strong postal system!
As far as server farms are concerned, that's best kept in private hands in a disaggregated network of equipment.