A common contemporary use of @ is in email addresses (using the SMTP system), as in [email protected] (the user jdoe located at the domain example.com). Ray Tomlinson of BBN Technologies is credited for having introduced this usage in 1971.[4][15] This idea of the symbol representing located at in the form user@host is also seen in other tools and protocols; for example, the Unix shell command ssh [email protected] tries to establish an ssh connection to the computer with the hostname example.net using the username jdoe.