Electronic mail (also known as e-mail or e-mailing) is a technique of exchanging messages (also known as "mail") between persons who use electronic devices to communicate. Consequently, email was intended as an electronic (digital) form of, or counterpart to, mail at a period when "mail" referred primarily to physical mail (hence the prefix e- + mail). As email grew in popularity, it became a ubiquitous (very widely used) communication medium, to the point where an e-mail address is often treated as a fundamental and necessary part of many processes in business and commerce as well as government, education, entertainment, and other spheres of daily life in most countries today. Email is the medium, and each communication delivered via it is referred to as an email.
Email's initial development dates back to the 1960s, however users could only send e-mail to other users of the same computer at the time. Some systems also enabled a sort of instant messaging, in which both the sender and the recipient had to be online at the same time to communicate. The origins of current Internet email services may be traced back to the ARPANET's early days, with specifications for encrypting email messages being published as far back as 1973. (RFC 561). It is quite similar to an email message sent in the early 1970s and to a simple email sent today. As the creator of networked email, Ray Tomlinson is credited with developing the first system capable of sending mail between users on various hosts over the ARPANET in 1971, using the @ sign to connect the user name with a destination server in a networked environment. By the mid-1970s, this was the format that was often referred to as email. At the time, however, email, like most computers, was mostly reserved for "computer geeks" working in certain fields such as engineering and the sciences, among others. The use of email grew widespread in company management, government, colleges, and the defense/military sectors throughout the 1980s and 1990s, although it was not widely adopted by the general public until much later in the decade. When web browsers were introduced in the late 1990s, email became more widely available to the general public, and was no longer seen to be a tool reserved for computer geeks in certain professions or businesses. By the 2010s, webmail (email as it was known throughout the web age) had achieved widespread acceptance.
Email is a kind of electronic communication that takes place across computer networks, most notably the Internet. In today's world, email systems operate on the store-and-forward principle. Email servers are responsible for accepting, forwarding, delivering, and storing mails. In order to send or receive messages or download information, neither users nor their computers are needed to be online at the same time; nonetheless, they must connect to a server (usually a mail server or a webmail interface).
Internet email was originally intended to be a text-only communication channel, but Multipurpose Internet Mail Extensions (MIME) have allowed it to transport text in various character sets as well as multimedia content attachments since its inception. International email, which uses UTF-8 to encode internationalised email addresses, is a standardised but not frequently used service.