According to the Universal Postal Union the oldest piece of mail is from Egypt 255 BCE. Herodotus credits the Persians with having a mail system similar to the Yam around 540 BCE (they only have accounts of this system, they have physical evidence for the Egyptian mail). Rome had a fairly extensive horse powered mail system that is very well documented. In general, couriers and systems of mail delivery existed throughout the major empires in antiquity. But the best is the Mongols (who are like, 1500 yeas later than the Persians so I'm not going to argue they are the OLDEST. But still the best.) My own hubris and laziness: a link to a comment I made last week about the Mongol yam