Phone numbers are an anachronism from the days of electromechanical phone exchanges[1]. These days we can name things more sensibly, so you can call Bob at exam

Phone numbers are an anachronism from the days of electromechanical phone exchanges[1]. These days we can name things more sensibly, so you can call Bob at example.com by just entering bob@example.com into your SIP client. That SIP client (or a server it is connected to) will then look up the SRV record[2] for _sip._tcp.example.com, connect to the SIP server it specifies, and ask it to be put in touch with Bob. [1] https://en.wikipedia.org/wiki/Strowger_switch https://en.wikipedia.org/wiki/Strowger_switch [2] https://en.wikipedia.org/wiki/SRV_record https://en.wikipedia.org/wiki/SRV_record