King Cyrus the Great went to great lengths to ensure that mail could reach the corners of his Kingdom, and worked with neighbouring countries to make sure that the mail got through and the system reached as far as it could. This process involved building roads and getting guards and massive diplomatic negotiations, but it lasted for a long time. Thus said Herodotus of Greece in the 5th Century BC: “It is said that as many days as there are in the whole journey, so many are the men and horses that stand along the road, each horse and man at the interval of a day’s journey; and these are stayed neither by snow nor rain nor heat nor darkness from accomplishing their appointed course with all speed” They've been delivering mail a long time then. My postman is a lovely guy, but I do wonder how sustainable daily deliveries are. It's only the junk mail that keeps it going.
I particularly enjoy watching Postie trying to work out how to reach the letter box when anything has "Do Not Bend" written on it ....