What if my SIP URI domain is different from the SIP proxy server FQDN (Fully Qualified Domain Name)?
With firmware 1.0.3.60 and later, you can put the your SIP URI domain name into the SIP Server field, and put the actual sip server FQDN into Outbound Proxy field. The phone will use the domain name in SIP Server as part of SIP URI but send and receive SIP messages through the SIP proxy server defined in the Outbound Proxy field.