How Email Was Invented: The First Network Message, the At Sign and SMTP

The history of email from the original documents: mailboxes on a single time-sharing computer, Ray Tomlinson's first network message and his choice of the at sign, the first header standard with From, Date and Subject, the SMTP conversation between mail servers, and how envelope, contents and POP3 get mail to you.

0:19 Before the network: one computer, many mailboxes

Mail between users of a single time-sharing computer already existed; a mailbox was just a file others could add to but not read.

Sources: Ray Tomlinson (original)

1:33 The first network message and the at sign

Tomlinson merged a file transfer program into SNDMSG and chose the at sign to separate the user from the host; the first messages went between two machines side by side.

Sources: Ray Tomlinson (original) · Internet Hall of Fame (original)

3:16 From, Date, Subject: the first header standard

RFC 561, in 1973, proposed a common format for the From, Date and Subject lines because every system wrote them differently.

Sources: RFC 561 (original) · Internet Hall of Fame (original)

4:40 SMTP: the conversation between mail servers

In 1982 RFC 821 defined SMTP, a strict, one step at a time dialogue of commands and numbered replies that can relay mail across networks.

Sources: RFC 821 (original) · Internet Hall of Fame (original)

6:30 Envelope, letter and mailbox: how mail reaches you

RFC 822 split a message into envelope and contents; POP3 let computers that are not always online fetch mail from a server.

Sources: RFC 822 (original) · RFC 1939 (original)

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Produced by Juan Pablo.