Email
The Business Encyclopedia states that email is "a method of communicating whereby an individual uses a computer or other electronic device to compose and send a message to another individual." These messages are often sent through computer systems that are linked through networks, from one system to another, using a modem and connected telephone lines, and often through a wireless transmission method.
Email has become a generic term for all electronic messaging from computer to computer, but real email is specific to an application which was deployed on the original Internet in 1971.