Hi all, I have a 3CX server on public IP that responds to the wrong port when it receives REGISTER messages from a Cisco 504 phone behind NAT. The Cisco 504 sends a REGISTER message to the 3CX server's public ip (port 5060) with a source port of e.g. 42634. The 3CX responds with a "407 Proxy Auth Req...", but sends it to the wrong port, that is port 5060. It should have sent it to port 42634 since this was the source port. Any idea how to solve this? Thanks in advance!