Ray Tomlinson, considered to be the godfather of email, has died, according to his employer, Raytheon Company. He was 74.
"A true technology pioneer, Ray was the man who brought us email in the early days of networked computers," Raytheon spokesman Mike Doble said in a statement.
Doble said Tomlinson died on Saturday morning but he did not know if he was at home and did not have a confirmed cause of death. Tomlinson worked in the company's Cambridge, Massachusetts, office.
An article in the Sydney Morning Herald reported that Tomlinson had died of a suspected heart attack.
The tech world reacted with sadness over the passing of Tomlinson, somewhat of a cult hero for his 1971 invention of a program for ARPANET, the Internet's predecessor, that allowed people to send person-to-person messages to other computer users on other servers.
"Thank you, Ray Tomlinson, for inventing email and putting the @ sign on the map," read a Tweet from Gmail's official Twitter account.
Internet pioneer Vinton Cerf called his death "very sad news."
Tomlinson was inducted into the Internet Hall of Fame in 2012.
"His work changed the way the world communicates and yet, for all his accomplishments, he remained humble, kind and generous with his time and talents," Doble said.
Originally from Amsterdam, New York, Tomlinson went to school at the Rensselaer Polytechnic Institute and MIT in the 1960s, and was working at research and development company Bolt Beranek and Newman - now Raytheon BBN Technologies - when he made his email breakthrough.
The program changed the way people communicate both in business and in personal life, revolutionizing how "millions of people shop, bank, and keep in touch with friends and family, whether they are across town or across oceans," reads his biography on the Internet Hall of Fame website.
According to a 1998 profile in Forbes magazine, Tomlinson showed a colleague his invention and then, famously, said, "Don't tell anyone! This isn't what we're supposed to be working on."
Around the time email started to become a household word, Tomlinson began receiving worldwide recognition for his achievement.
In 2000, he received the George R. Stibitz Computer Pioneer Award from the American Computer Museum. From there followed honors that included a Webby Award from the International Academy of Digital Arts and Science, and an Innovation award from Discover magazine, and the Eduard-Rhein Cultural Award, according to his biography.
Thank you, Ray Tomlinson, for inventing email and putting the @ sign on the map. #RIP— Gmail (@gmail) March 6, 2016