SIP Registrar Service
From XMission Wiki
XMission provides a SIP server free of charge.
sip.xmission.com is a SIP server for use by XMission customers. It will allow you to send and receive SIP phone calls to other SIP clients. You can receive calls at <xm_username>@xmission.com. You can place calls to any other SIP server on any other domain, but can not place calls to the PSTN (public telephone network).
Go to http://sip.xmission.com to sign up. Instructions will follow.
After your account is created follow these instructions: In your SIP Client software, set server to sip.xmission.com, username to your sip_username, password to your sip_password. Thats it!
