IIS 7 and Above
FTP works on LAN but not from WAN
Re: FTP works on LAN but not from WAN
Nov 27, 2011 06:07 AM|lextm|LINK
IIS.net site documents cannot tell you what happens on your network. You should understand that any devices in between can filter out the FTP packets.
Using tools such Network Monitor or Wireshark should help you better analyze the network connections, and provide you hints on what is the problem.
A network expert is needed, and you should try to find a guy like that locally to help you.