Story highlights In 1971, Ray Tomlinson came up with direct email messages

His system helped lay the groundwork for the email and Internet explosion of the 1980s and '90s

(CNN) Ray Tomlinson, widely credited as the creator of email, has died, his employer, Raytheon, told CNN on Sunday. He was 74.

Tomlinson invented direct email messages in 1971. Before his invention, electronic messages could be shared only on a very limited network.

Among those paying tribute was Gmail, one of many offshoots of Tomlinson's creation.

Thank you, Ray Tomlinson, for inventing email and putting the @ sign on the map. #RIP — Gmail (@gmail) March 6, 2016

"Thank you, Ray Tomlinson, for inventing email and putting the @ sign on the map," Gmail's Twitter account said.

Tomlinson, a graduate of Rensselaer Polytechnic Institute and MIT, was working for a Boston technology firm in 1971 when he decided to figure out a way for people to send messages via computer. At the time, Tomlinson recalled, ARPANET -- the Internet's predecessor -- was fairly new and the idea of sending messages from computer to computer was novel. Computers themselves were often giant mainframe beasts that filled entire rooms.