E-mail is short for electronic mail, messages communicated via computer rather than paper. Although the term e-mail encompasses a variety of computer-to-computer transactions, it is most associated with communication via the Internet. The Internet is a vast computer network made up of many individual computers around the world. E-mail is the most-used Internet application, permitting people to exchange greetings and information with incredible speed. It is estimated that more than 15 billion e-mail messages are sent every year.

In the early 1960s computers were room-sized machines that were often shared by many people. These time-sharing computer systems featured individual terminals hooked up to the host computer. Users could leave messages for one another by storing them in a particular file on the computer or by using an internal mail delivery program. By the late 1960s the ARPAnet had been formed. This was a US Department of Defense project in...