I am using nexVortex with my 3cx. I can receive inbound calls but can't make outbound. The NexVortex server sends me "603 declined" error. NexVotex guys are telling me that "the 3CX PBX system is not sending the right MTU for the length of message and causing the content length message error." Content-Length should be 256, my 3CX is sending 252. Please help.