How to send letters in ancient times?

Flying pigeons pass books, hehe, this is naturally impossible. In ancient times, we had a post station, which could be a transfer station for letters or a place for pedestrians to stop and turn their feet. Mainly use Malay as a means of communication. If it is an urgent letter, it will be delivered by the best horse. Well, especially in wartime, it was difficult to find a good colt before: on the one hand, it refers to the fighting capacity, on the other hand, it refers to the speed and quality of the battle report transmission. Hehe, I wonder if you are satisfied?