is connection of program licated in C:\Program Files\3CX Phone System\Bin\3CXMediaServer.exe to the IP and port > > 192.168.1.53->80.66.88.217:7406 OK or should be blocked ?
I do not entirely know your network topology, however 7406 is within the range of "3CX Media Server (RTP) – LAN audio/video/t38 streams" outlined here: https://www.3cx.com/docs/ports/