posthorse

noun

1. A horse ridden by a postrider to carry mail.

   “His name was Joe, and he lived at Skroperud in Ullensaker. He built himself a new house there, and he had two or three fat cows and a horse, the like of which was not to be found in the whole parish; the horse was often used as post-horse between Mo and Trogstad, and Joe didn't seem to care much how the beast was used, for fat he was and fat he remained.”