The history of modern, global Internet email services reaches back to the early ARPANET, with standards for encoding email messages proposed as early as 1973 (RFC 561).
Historically, the term electronic mail was used generically for any electronic document transmission.For example, several writers in the early 1970s used the term to describe fax document transmission.As a result, it is difficult to find the first citation for the use of the term with the more specific meaning it has today.Electronic mail is a method of exchanging digital messages between computer users; Email first entered substantial use in the 1960s and by the 1970s had taken the form now recognised as email.Email operates across computer networks, which in the 2010s is primarily the Internet.
Some early email systems required the author and the recipient to both be online at the same time, in common with instant messaging.
Today's email systems are based on a store-and-forward model.
Email servers accept, forward, deliver, and store messages.
Neither the users nor their computers are required to be online simultaneously; they need to connect only briefly, typically to a mail server, for as long as it takes to send or receive messages.
Originally an ASCII text-only communications medium, Internet email was extended by Multipurpose Internet Mail Extensions (MIME) to carry text in other character sets and multimedia content attachments.
International email, with internationalized email addresses using UTF-8, has been standardized, but as of 2016 not widely adopted.