The first email was sent in 1971...between two computers that were side-by-side.
These two computers were connected through the original online network, ARPANET, which was run by the United States Defense Department. The first message sent through the network to another computer was in 1969. The message was "Lo". The engineers working on it attempted to send the word "Log" but one of the computers crashed after the "O".
The first email transmission was sent in 1971. Ray Tomlinson, the engineer behind ARPANET's email system and the man who came up with using the @ sign for email, said that the first email he sent was something insignificant. The actual contents of the first email were "entirely forgettable" and most likely something akin to "QWERTYUIOP"