In a town in which I used to live, the post office is now a gynecologist's office. However, because history features heavily in that town's history, historic buildings are heavily preserved there, so the medical facility still appears, at least externally, to be a post office.

A friend of mine claims that he once went there and asked to "put something in a slot," only to be rudely turned away. Given the phrasing, I'm pretty sure he was joking.