Surprising though it may seem, with some limited exceptions, it's illegal for a private party to deliver a letter to another private party without paying the US

Surprising though it may seem, with some limited exceptions, it's illegal for a private party to deliver a letter to another private party without paying the US Postal Service. The term to search for is "Private Express Statutes": https://en.wikipedia.org/wiki/Private_Express_Statutes https://en.wikipedia.org/wiki/Private_Express_Statutes. This article (titled "Universal Service and the Postal Monopoly: A Brief History") goes into more depth: https://about.usps.com/universal-postal-service/universal-service-and-postal-monopoly-history.pdf https://about.usps.com/universal-postal-service/universal-se...