Dial failure calling a SIP Domain without specifying a region

• If you do a <Dial><Sip> without specifying a region

• Dial the regional SIP domain. For instance: <Dial><Sip>username@yoursipdomain.sip.us1.twilio.com</Dial></Sip>.

Note the us1 above that is specifying that you are calling a SIP endpoint registered to the US1 (North Virginia) data center.