First, I want to say the 3CXPhone for Android app is great!. Looks good and is well done. I am able to connect to 3CX v8 over our internal WIFI. However when connecting over 3G, the phone registers (the server log concurs). When dialing voicemail, the SIP INVITE string has 999@external address, instead of 999@internal address, thus 3CX rejects the call. So in the phone I have the following configured. User/Pwd for the extension Internal Server: IP or DNS name of the internal server External Server: external domain name (www) STUN: 3cx stun server Enable 3G: checked. Proximity Sensor: checked all other things are default I would have expected that the SIP invite would contain the value from the Internal Server value. The External Server used for connection. Any ideas? BTW, I can successfully call the 3CXPhone from the internal Polycom phones.