The man credited with inventing the email, Ray Tomlinson, has died at the age of 74.
In 1971 Mr Tomlinson came up with the idea of sending electronic messages from one person to another.
He also pioneered the use of the 'at' symbol, the key feature used in all email addresses today.
He wrote the first modern email while working as a computer engineer in Boston.
His death was confirmed by his employer, Raytheon Company, who in a statement described him as a "true technology pioneer".
A tweet from Gmail's official Twitter account paid tribute to Mr Tomlinson, saying he had put the @ sign on the map.
Thank you, Ray Tomlinson, for inventing email and putting the @ sign on the map. #RIP— Gmail (@gmail) 6 March 2016