our office have a mail server and web server which at china.
recenlty, we cann't connect to the server from HK to china server, but if connect from china -> china without problem
We used this server over 4 year, but no any problem...
anyone know what we need to do now? as checked HK/china isp, they said no any problem for the connection.
By the way, I can ping/ tracert the email server, but if I use telnet domain 443 or 80, it will fail..., Mean I can reach the server, but cannot reach the Port 443/ 80.
But if do the same at other china city, which is ok to telnet.
You IP being filtered by Great Firewall of China (GFC). Try changing the public IP address and the telnet to the port should work for a while. Long term solution is to have VPN tunnel to avoid open those ports to public.