I have a SPA-921 that is on the outside of the 3CX network. I can hear the outgoing audio on my other phone with no problem. The SIP phone will not recieve any audio. I have checked the Firewall and ports 5060 7000-7499 9000-9015 3478 are all open on both the external and the 3CX firewall. The STUN does not seem to want to resolve the SIP's actual outside IP. There are no error messages when it calls it simply resolves it at email@example.com I am out of ideas. If I register the phone directly with the VOIP provider ( Callcentric ) it works fine. What am I missing.