Respuesta :
Answer: Some of the earliest known postal systems stem from Egypt, Persia, India, and China. ... In Ancient Persia, during the period of 550 BC to 521 BC, a true postal system was developed in Assyria. It is disputed whether it was Cyrus the Great or his successor Darius I, who was responsible.
Explanation:
unites a country
some guarantees:
1. the secrecy of the message is safe
2.the message has reached the intended party
3.the message came from the person whose name os written on the letter
made for kingdoms who have grown large and need something more than a town herald or crier