Mail

Mail is part of a postal system which itself is a system wherein written documents typically enclosed in envelopes, and also small packages containing other matter, are delivered to destinations around the world. Anything sent through the postal system is called mail or post.[1]

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 stamps, but postage meters are also used for bulk mailing. In general government monopolies only extend parcel (non-mail) delivery to courier services which provide express delivery.[clarify]

Postal systems often have functions other than merely 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.