The mail or post is a system for physically transporting documents and other small packages, as well as a term for the postcards, letters, and parcels themselves. A postal service can be private or public, though many governments place restrictions on private 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. Modern private postal systems are typically distinguished from national postal agencies by the names "courier" or "delivery service".
Postal authorities often have functions other than transporting letters. In some countries, a postal, telegraph and telephone (PTT) service oversees the postal system, as well as hasa authority over telephone and telegraph systems. Some countries' postal systems allow for savings accounts and handle applications for passports. The Universal Postal Union (UPU), established in 1874, includes 192 member countries and sets the rules for international mail exchanges.
Why does the US Postal Service have mailmen, but the Royal Mail has postmen?
The English language in the US (when mail/post-delivery was starting out and the post office was just a thought) was influenced by more than one culture, whereas 'post' was decidedly more English. "Mail" has and ''old French'' origin.
The word mail comes from the Medieval English word male (spelled that way until the 17th century), which was the term used to describe a traveling bag or pack. The French have a similar word, malle for a trunk or large box, and mála is the Irish for a bag. In the 17th century the word mail began to appear as a reference for a bag that contained letters: "bag full of letter" (1654). Over the next hundred years the word mail began to be applied strictly to the letters themselves, and the sack as the mailbag. In the 19th century the British usually referred to mail as being letters that were being sent abroad (i.e. on a ship), and post as letters that were for localized delivery; in the UK the Royal Mail delivers the post, while in the USA the US Postal Service delivers the mail. The term e-mail (short for "electronic mail") first appeared in 1982. The term snail-mail is a retronym that originated in 1983 to distinguish it from the quicker e-mail.