Logs and More Info
I've changed my debugging mode to verbose and I've pasted the server log below. We are using Zingo as our VOIP provider and 3cx is running on a computer that is on the DMZ. We are not using a gateway
11:54:18.085 StratLink:

nHangUp [CM104001] Call(15): Ext.102 hung up call; cause: BYE; from IP:192.168.2.15
11:52:42.069 CallLegImpl:

nConnected [CM103001] Call(15): Created audio channel for Ext.102 (192.168.2.15:16432) with Media Server (192.168.2.50:7110)
11:52:42.054 StratInOut:

nConnected [CM104005] Call(15): Setup completed for call from Ln:10000@Zingo to Ext.102
11:52:39.335 CallConf:

nProvisional [CM103003] Call(15): Ext.101 is ringing
11:52:36.569 StratLink:

nHangUp [CM104001] Call(13): Ext.101 hung up call; cause: BYE; from IP:192.168.2.14
11:52:36.523 StratLink:

nHangUp [CM104001] Call(14): Ext.103 hung up call; cause: BYE; from IP:192.168.2.12
11:52:34.148 MediaServerReporting:

TMFhandler [MS211000] Call(15) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:52752 arrived. in-band DTMF tone detection is turned off.
11:52:23.148 CallLegImpl:

nConnected [CM103001] Call(15): Created audio channel for Ln:10000@Zingo (207.218.174.156:52752) with Media Server (67.53.129.195:9028)
11:52:23.116 CallConf:

nIncoming [CM103002] Call(15): Incoming call from 15405831613 (Ln:10000@Zingo) to sip:
[email protected]
11:51:18.069 MediaServerReporting::RTPSender [MS104000] Call(14) Ext.103: (ACTIVE) RTP stream to 192.168.2.12:16480 restored.
11:51:18.069 StratLink:

nHangUp [CM104001] Call(12): Ln:10000@Zingo hung up call; cause: BYE; from IP:69.25.48.83
11:50:57.913 MediaServerReporting::RTPSender [MS004000] Call(14) Ext.103: (ACTIVE): Can't send RTP stream to 0.0.0.0:16480 destination unreachable
11:50:55.273 CallLegImpl:

nConnected [CM103001] Call(14): Created audio channel for Ext.103 (192.168.2.12:16480) with Media Server (192.168.2.50:7104)
11:50:55.257 StratInOut:

nConnected [CM104005] Call(14): Setup completed for call from Ln:10000@Zingo to Ext.103
11:50:51.507 CallConf:

nProvisional [CM103003] Call(14): Ext.103 is ringing
11:50:45.819 MediaServerReporting:

TMFhandler [MS211000] Call(14) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:53772 arrived. in-band DTMF tone detection is turned off.
11:50:37.132 MediaServerReporting::RTPSender [MS104000] Call(13) Ext.101: (ACTIVE) RTP stream to 192.168.2.14:16418 restored.
11:50:36.913 CallLegImpl:

nConnected [CM103001] Call(14): Created audio channel for Ln:10000@Zingo (207.218.174.156:53772) with Media Server (67.53.129.195:9026)
11:50:36.726 CallConf:

nIncoming [CM103002] Call(14): Incoming call from 16157409724 (Ln:10000@Zingo) to sip:
[email protected]
11:50:27.429 MediaServerReporting::RTPSender [MS004000] Call(13) Ext.101: (ACTIVE): Can't send RTP stream to 0.0.0.0:16418 destination unreachable
11:50:24.663 CallLegImpl:

nConnected [CM103001] Call(13): Created audio channel for Ext.101 (192.168.2.14:16418) with Media Server (192.168.2.50:7092)
11:50:24.663 StratInOut:

nConnected [CM104005] Call(13): Setup completed for call from Ln:10000@Zingo to Ext.101
11:50:12.038 CallConf:

nProvisional [CM103003] Call(13): Ext.103 is ringing
11:50:06.929 MediaServerReporting:

TMFhandler [MS211000] Call(13) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:53800 arrived. in-band DTMF tone detection is turned off.
11:50:02.835 CallLegImpl:

nConnected [CM103001] Call(13): Created audio channel for Ln:10000@Zingo (207.218.174.156:53800) with Media Server (67.53.129.195:9024)
11:50:02.804 CallConf:

nIncoming [CM103002] Call(13): Incoming call from 19786870999 (Ln:10000@Zingo) to sip:
[email protected]
11:49:48.163 ListenConnect [CM114000] SL: connected DellOwner1:0/PHPExtension_0 at [DellOwner1]/PHPExtension_0
11:49:46.413 CallLegImpl:

nConnected [CM103001] Call(12): Created audio channel for Ext.102 (192.168.2.15:16426) with Media Server (192.168.2.50:7086)
11:49:46.413 StratInOut:

nConnected [CM104005] Call(12): Setup completed for call from Ln:10000@Zingo to Ext.102
11:49:44.054 CallConf:

nProvisional [CM103003] Call(12): Ext.103 is ringing
11:49:38.304 MediaServerReporting:

TMFhandler [MS211000] Call(12) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:50786 arrived. in-band DTMF tone detection is turned off.
11:49:29.054 CallLegImpl:

nConnected [CM103001] Call(12): Created audio channel for Ln:10000@Zingo (207.218.174.156:50786) with Media Server (67.53.129.195:9022)
11:49:28.991 CallConf:

nIncoming [CM103002] Call(12): Incoming call from 17202837714 (Ln:10000@Zingo) to sip:
[email protected]
11:49:26.663 CallMgr:

umThread::thread [CM000003] *!* Exception catched: unknown
11:49:16.101 CallMgr:

umThread::thread [CM000003] *!* Exception catched: unknown
11:49:14.382 StratLink:

nHangUp [CM104001] Call(11): Ln:10000@Zingo hung up call; cause: unknown
11:49:01.569 CallMgr:

umThread::thread [CM000003] *!* Exception catched: unknown
11:48:54.148 CallMgr:

umThread::thread [CM000003] *!* Exception catched: unknown
11:48:45.335 CallMgr:

umThread::thread [CM000003] *!* Exception catched: unknown
11:48:44.288 CallLegImpl:

nConnected [CM103001] Call(11): Created audio channel for Ext.102 (192.168.2.15:16424) with Media Server (192.168.2.50:7078)
11:48:44.273 StratInOut:

nConnected [CM104005] Call(11): Setup completed for call from Ln:10000@Zingo to Ext.102
11:48:38.288 CallConf:

nProvisional [CM103003] Call(11): Ext.101 is ringing
11:48:32.491 MediaServerReporting:

TMFhandler [MS211000] Call(11) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:53084 arrived. in-band DTMF tone detection is turned off.
11:48:24.476 CallLegImpl:

nConnected [CM103001] Call(11): Created audio channel for Ln:10000@Zingo (207.218.174.156:53084) with Media Server (67.53.129.195:9020)
11:48:24.444 CallConf:

nIncoming [CM103002] Call(11): Incoming call from 19786870999 (Ln:10000@Zingo) to sip:
[email protected]
11:46:42.991 StratLink:

nHangUp [CM104001] Call(10): Ext.102 hung up call; cause: BYE; from IP:192.168.2.15
11:45:28.694 CallLegImpl:

nConnected [CM103001] Call(10): Created audio channel for Ext.102 (192.168.2.15:16420) with Media Server (192.168.2.50:7070)
11:45:28.679 StratInOut:

nConnected [CM104005] Call(10): Setup completed for call from Ln:10000@Zingo to Ext.102
11:45:20.429 CallConf:

nProvisional [CM103003] Call(10): Ext.101 is ringing
11:45:15.351 MediaServerReporting:

TMFhandler [MS211000] Call(10) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:50398 arrived. in-band DTMF tone detection is turned off.
11:45:09.601 CallLegImpl:

nConnected [CM103001] Call(10): Created audio channel for Ln:10000@Zingo (207.218.174.156:50398) with Media Server (67.53.129.195:9018)
11:45:09.569 CallConf:

nIncoming [CM103002] Call(10): Incoming call from 12018392272 (Ln:10000@Zingo) to sip:
[email protected]
11:41:20.944 StratLink:

nHangUp [CM104001] Call(9): Ln:10000@Zingo hung up call; cause: BYE; from IP:69.25.48.83
11:39:35.906 CallLegImpl:

nConnected [CM103001] Call(9): Created audio channel for Ext.102 (192.168.2.15:16418) with Media Server (192.168.2.50:7062)
11:39:35.906 StratInOut:

nConnected [CM104005] Call(9): Setup completed for call from Ln:10000@Zingo to Ext.102
11:39:12.156 CallConf:

nProvisional [CM103003] Call(9): Ext.101 is ringing
11:39:07.156 MediaServerReporting:

TMFhandler [MS211000] Call(9) Ln:10000@Zingo: DTMF (RTP) from 207.218.174.156:50620 arrived. in-band DTMF tone detection is turned off.
11:38:57.468 CallLegImpl:

nConnected [CM103001] Call(9): Created audio channel for Ln:10000@Zingo (207.218.174.156:50620) with Media Server (67.53.129.195:9016)