Mail, or post, is a method for transmitting information and tangible objects, wherein written documents, typically enclosed in envelopes and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.

In principle, a postal service can be private or public. Governments often place restrictions on private postal delivery systems. Since the mid 19th century national postal systems have generally been established as government monopolies with a fee on the article prepaid. Proof of payment is often in the form of adhesive postage stamps, but postage meters are also used for bulk mailing.

Postal systems often have functions other than sending letters. In some countries, the postal system also has some authority over telephone and telegraph systems. In others, postal systems allow for savings accounts and handling applications for passports.

Early postal systems

The art of communication by written documents carried by an intermediary from one person or place to another almost certainly dates back nearly to the invention of writing. However, development of formal postal systems occurred much later. The first documented use of an organized courier service for the diffusion of written documents is in Egypt, where Pharaohs used couriers for the diffusion of their decrees in the territory of the State (2400 BC). This practice almost certainly has roots in the much older practice of oral messaging and may have been built on a pre-existing infrastructure.