Many countries have postal savings systems, often very significant. The first was in the UK, 1861.[1] In the US, existed 1911 - 1967, started in the wake of the Panic of 1907.[2] The list of countries with postal savings is extensive,[1] with the Japan Post Bank being among the largest savings institutions worldwide.[3] France's La Poste Group website[4] highlights "eliminating banking customer refusal" and provides an extensive suite of services.

Back in the States, it's interesting that the U.S. Constitution, Article 1, Section 8, explicitly gives Congress the power "To establish Post Offices and post Roads." A few lines earlier the same article grants Congress the power "To borrow Money on the credit of the United States." Would it then seem odd for the Congress to be assumed to have the power to create postal bonds, so common in much of the world?

[Addendum]

Might not be such a stretch then to imagine a Postal Savings System or something similar with great reach in the US, potentially encompassing much of what commercial banks handle today. The advantages including stability and availability, and perhaps even efficiency. Perhaps Hyman Minsky might have wished for things to... go postal?

[1] https://en.wikipedia.org/wiki/Postal_savings_system

[2] https://en.wikipedia.org/wiki/United_States_Postal_Savings_S...

[3] https://en.wikipedia.org/wiki/Japan_Post_Bank

[4] https://www.lapostegroupe.com/en/banking-accessibility-la-po...