Electronic mail, most commonly called email or e-mail since around 1993 is a method of exchanging digital messages from an author to one or more recipients. Email operates across the Internet or other computer networks.
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 connect only briefly, typically to a mail server, for as long as it takes to send or receive messages.