The first credible claim for the development of a real postal system comes from Ancient Persia, but the point of invention remains in question.

The best documented claim (Xenophon) attributes the invention to the Persian King Cyrus the Great (550 BCE), while other writers credit his successor Darius I of Persia (521 BCE).

Other sources claim much earlier dates for an Assyrian postal system, with credit given to Hammurabi (1700 BCE) and Sargon II (722 BCE).

Mail may not have been the primary mission of this postal service, however.

The role of the system as an intelligence gathering apparatus is well documented, and the service was (later) called angariae, a term that in time came to indicate a tax system.

The Old Testament (Esther, VIII) makes mention of this system: Ahasuerus, king of Medes, used couriers for communicating his decisions.

The Persian system works on stations (called Chapar-Khaneh), where the message carrier (called Chapar) would ride to the next post, whereupon he would swap his horse with a fresh one, for maximum performance and delivery speed.

Herodotus described the system in this way: "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".