1971: Ray Tomlinson, a computer engineer working for Bolt Beranek and Newman in Cambridge, Massachusetts, developed a system for sending messages between computers that used the @ symbol to identify addresses. He now can't remember the first message he sent, or the exact date he sent it.

Tomlinson's system gained popularity by linking up users on Arpanet, the US department of defence system that became the basis for the internet.

1972: Larry Roberts - also at work on Arpanet - writes the first email management program that develops the ability to list, select, forward, and respond to messages.

1976: Queen Elizabeth II sends an email message on Arpanet, becoming the first head of state to do so.

1988: Steve Dorner invents Eudora, an application that gave a popular face to email by providing a graphical user interface for email management.

1989: The first release of Lotus Notes email software. 35,000 copies are sold in the first year.

1996: Microsoft releases Internet Mail and News 1.0, a feature of its third release of Internet Explorer. This is later renamed Outlook.

1996: A few companies - including the fledgling Hotmail - begin to offer free, use-anywhere, internet email.

1997: About 10 million users world wide have free web mail accounts.

1998: Microsoft buys Hotmail for $400m (£283m).

2001: Email celebrates its 30th anniversary with virtually every business in the developed world signed on.