If you’ve ever sent an e-mail, you can thank Raymond Samuel Tomlinson for putting the @ symbol there.

On Friday, Tomlinson died of suspected heart failure. He was 74.

Tomlinson was born in Amsterdam, New York in 1941, and he earned a master’s degree from the Massachusetts Institute of Technology. In 1967, he joined Bolt Beranek and Newman (BBN), a company that played a key role in the development of the ARPANET, a precursor to the modern Internet.

In 1971, according to the Internet Hall of Fame, he wrote the first ARPANET mail client, combining the existing SNDMSG and CPYNET programs. Tomlinson himself came up with the idea of using the @ symbol as a way to separate local e-mails from those that could be sent to external networks through the user@host syntax.

As he wrote on his own website in the early 1990s: