There’s a movie called The Postman. It’s based on a novel by David Brin. The story, in both the book and the movie, is about how a guy accidentally restarts civilization by delivering the mail. The actual plot is more complicated than that. The movie is sentimental and obvious and heavy handed. The novel takes some side tours into intelligent computers and supersoldiers that are pretty basic for a science fiction story but might seem a little weird if one had seen the film first.
I enjoy both versions of the story. But I really hope I never have to deliver mail in a radioactive wasteland. On a horse.