The story
In 1875, post offices were authorized to offer savings products.
In 1881 the French state established the Caisse Nationale d'Épargne (CNE) to manage retail savings collected through the French network of post offices. The CNE thus competed for the collection of small retail savings with the local Caisses d'Épargne (also known in that context as Caisses d'épargne ordinaires) which were private-sector entities.
The Law of January 7, 1918, introduced postal current accounts and checks in France.
In 1988, Sogéposte, the financial subsidiary of La Poste and the Caisse des Dépôts et Consignations, was established.
In 2012, the company set out to be a benchmark partner for the public sector, focusing on working with all regional stakeholders. By 2015, La Banque postale's commitments had been realized, now being recognized as the reference bank for local authorities concerning financing and banking services, as well for stakeholders dealing with social housing, local institutions, public health-care establishments and semi-public corporations.
From Wikipedia’s article on La Banque postale, shared under CC BY-SA 4.0.5