How to Block Port 25 on a Windows Firewall

Written by chris hoffman Google
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How to Block Port 25 on a Windows Firewall
Firewalls protect computers against undesired network traffic. (ethernet connections image by TekinT from

Windows comes with an integrated firewall that's on by default. Firewalls block incoming traffic and control which other traffic is allowed using firewall rules. Windows Firewall normally blocks traffic on port 25 and other ports, but if you've set up a firewall rule to accept all traffic, port 25 will be unblocked. You can manually block port 25 by creating a blocking firewall rule, which overrides any rule accepting traffic on port 25. Port 25 is used for mail servers and is often blocked to reduce spam and other unsolicited Internet traffic.

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  1. 1

    Click "Start," "Control Panel," "System and Security" and "Windows Firewall."

  2. 2

    Click "Advanced Settings" in the left sidebar of the Windows Firewall window.

  3. 3

    Click "Inbound Rules" at the left side of the advanced firewall settings window.

  4. 4

    Click "New Rule" at the right side of the window.

  5. 5

    Click "Port" in the wizard window and click "Next."

  6. 6

    Type "25" into the "Specific Local Ports" box and click "Next."

  7. 7

    Click "Block the Connection" and click "Next."

  8. 8

    Block port 25 on all network profiles by clicking "Next."

  9. 9

    Type a name for the port-blocking firewall rule into the "Name" box.

  10. 10

    Click "Finish."

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