Raymond Samuel Tomlinson was an American computer programmer who implemented the first email program on the ARPANET system, the precursor to the Internet, in 1971; 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 Internet Hall of Fame in its account of his work commented "Tomlinson's email program brought about a complete revolution, fundamentally changing the way people communicate." He is credited with the invention of the TCP three-way handshake which underlies HTTP and many other key Internet protocols.

The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first computer networks to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the Internet. The ARPANET was established by the Advanced Research Projects Agency (ARPA) of the United States Department of Defense.