Raymond Samuel Tomlinson (April 23, 1941 – March 5, 2016) was a pioneering American computer programmer who implemented the first email program on the ARPANET system, the precursor to the Internet, in 1971; he is internationally known and credited as the inventor of email. It was the first system able to send mail between users on different hosts connected to ARPANET. 

Previously, mail could be sent only to others who used the same computer. To achieve this, he used the @ sign to separate the user name from the name of their machine, a scheme which has been used in email addresses ever since. 

The first email Tomlinson sent was a test. 

At first, his email messaging system was not considered important. Its development was not a directive of his employer, with Tomlinson merely pursuing it "because it seemed like a neat idea".

Tomlinson said he preferred "email" over "e-mail", joking in a 2010 interview that "I'm simply trying to conserve the world's supply of hyphens" and that "the term has been in use long enough to drop the hyphen".

Email operates across computer networks, primarily the Internet. Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simultaneously; they need to connect, typically to a mail server or a webmail interface to send or receive messages or download it.

According to en.wikipedia