working. I've also tried port-fowarding and DMZ in the modem, to no avail. So my conjecture is that the ISP has decided to block packets it considers unworthy before they reach the modem. Is this at all likely? How can I test/confirm the conjecture? If it is confirmed, what can I do? Needless to say, ISP "technical support" has so far been useless.

Smaller local ISP's usually do not block Port 25. Note that if your ISP is Comcast you can update your account to a Business Class account with full access to port 25. In the case you are connected through AT&T or Verizon, port 25 can be unblocked at the request. You can easily check whether you are affected by port blocking by using eMail networking - How to check if a port is blocked on a The best way to check if a port is blocked is to do a port scan from the client machine. There are many ways to do a port scan but since you mentioned being on Windows then I will suggest the Microsoft command line utility PortQry and the Graphical version PortQryUI. To test all open ports: portqry.exe -n #.#.#.# To test a specific port: Steam Community :: Guide :: Bypass ISP blocking for port Open a Windows PowerShell console and paste this, check if your ISP do block port 6667 or not. Test-NetConnection peerchat.server.cnc-online.net-port 6667. If you results come with: TcpTestSucceeded : False. Mean your ISP is blocking port 6667. Start Unblocking Since only port 6667 get blocked, it's time to redirect by using proxy Port Forwarding: How to Check Your Router for Open Ports

Very few ISPs block ALL ports. Most residential ISPs will block the common ports (80, 443, 21, 22, 23, 53, etc). You have to use uncommon ports (anything over 10000 is for sure safe) Most ISPs that block all inbound ports are shadier ones (mostly

How to forward ports if my ISP blocks all inbound Very few ISPs block ALL ports. Most residential ISPs will block the common ports (80, 443, 21, 22, 23, 53, etc). You have to use uncommon ports (anything over 10000 is for sure safe) Most ISPs that block all inbound ports are shadier ones (mostly How to check if your ISP is monitoring/blocking which ports?

IP address: enter your IP followed by : and the port id – eg 10.0.0.1:1025 allow local clients (check this box) external Ip addresses (leave blank) In the example above, GMS will bind to IP 10.0.0.1 on port 1025, in addition to the standard port 25. Once you have done this, click finish and then go to the System->Control services GUI.

How to Open Your Port 80 Behind a Firewall: 8 Steps Find your router's IP address. In order to access your router's page, you must know your router's IP …