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Email Addresses Use @ Because Ray Tomlinson's 1971 Terminals Had About a Dozen Punctuation Marks, and Only @ Meant 'At'
Ray Tomlinson, who sent the first network email in late 1971, said he picked @ to split a user's login name from the host because it meant 'at', it appeared in nobody's name, and his Model 33 terminals offered few other choices.
Tomlinson was a programmer at Bolt, Beranek and Newman, on a small team building TENEX, a time-sharing system for Digital PDP-10 computers. He was improving SNDMSG, a mail program that only delivered to other users of the same machine. He had also written CPYNET, an experimental program for sending files over the ARPANET.
Putting the two together was, in his words, “a no-brainer.” A mailbox was just a file other users could append to, so once CPYNET could append, SNDMSG could drop a message into a mailbox on another computer. What was missing was a way to say which computer. “I chose to append an at sign and the host name to the user’s (login) name,” he wrote.
He gave the reasoning in a late-1990s interview for the Open University, replayed in its Internet at 40 series. “I sort had a fairly limited set of characters I could choose from,” he said. The Model 33 terminals they were using “had only about a dozen punctuation marks anyway and the only one that really made sense was the @ sign since that meant this user was @ that computer.”
The second reason was practical. “I also chose it because it didn’t appear in anybody’s name,” Tomlinson said, so a program never had to guess whether an @ was part of a name or the break between name and machine. He added: “Of course that’s no longer true.”
He had a third angle in a 2009 interview with NPR’s Guy Raz, which NPR republished when he died in 2016. The @ turns an address into a phrase, “user ‘at’ host,” and as he put it, “It’s the only preposition on the keyboard.”
Nobody kept the first email, including the man who sent it. Tomlinson sent test messages between two machines “literally side by side,” connected only through the ARPANET, and called them “entirely forgettable and I have, therefore, forgotten them.” His best guess on his page is “QWERTYUIOP or something similar.” What he does remember is the first one that went to anyone else: a note to his group “explaining how to send messages over the network.”
Tomlinson said in the Open University interview that the first program “only lasted probably six to eight months” before better mail programs replaced it. The @ outlasted all of them. The open question is whether it survives the next shift, as more messages go to handles inside apps that never show a host at all.