Electronic mail (e-mail or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Invented by Ray Tomlinson, e-mail was first put into limited use in the 1960s and by the mid-1970s had taken the form now known as e-mail. Email operates in all computer networks, which is currently primarily the Internet. Some early email systems require the writer and recipient to both be online at the same time, the same as instant messaging. The email system is currently based on the store-and-forward model. The e-mail server accepts, forwards, sends and saves messages. Both users and their computers are not required to be online simultaneously; they only need to be briefly connected, usually to the email server or webmail interface, as long as it is necessary to send or receive messages.

Originally an ASCII text communication media only, Internet e-mails were extended by Multipurpose Internet Mail Extensions (MIME) to carry text in a collection of other characters and multimedia content attachments. International email, with international email addresses using UTF-8, has been standardized, but in 2017 it has not been widely adopted.

The history of modern Internet email services reached back to the initial ARPANET, with standards for coding e-mail messages published in early 1973 (RFC 561). Email messages sent in the early 1970s are very similar to the basic emails sent today. Email had an important role in creating the Internet, and the conversion from the ARPANET to the Internet in the early 1980s produced the core of current services.