The first email was sent by a programmer to himself in 1971

Ray Tomlinson sent the first networked email in 1971 using the ARPANET network. He chose the @ symbol to separate the username from the host computer — a decision he described as obvious at the time but which has defined internet addressing ever since. Tomlinson couldn't remember what the first message said, suggesting it was a test string like 'QWERTYUIOP'. Email predates the web by nearly two decades and remains, by volume of users, the world's dominant communication technology.

Source: Hafner & Lyon, Where Wizards Stay Up Late (1996)