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Issue: Outgoing Mail Blocked on Port 25  

The error Outgoing mail blocked on port 25 occurs due to the misconfiguration of your ISP settings. The outgoing port 25 is usually blocked to prevent viruses and spams over your network. To fix this issue on Microsoft Outlook 2007, follow the below-mentioned steps.

outgoing mail blocked on port 25
  • On your Windows 10 computer, click the Start menu and type ‘outlook’ in the search panel.
  • From the search result, give a double-click on the Microsoft Outlook app to launch it.
  • Once the Outlook app is launched, click the Tools menu at the top-left corner of the screen.
  • Select the Email Accounts option and click the View or Change existing email accounts button.
  • Click the Next button and select the email that is causing the trouble of outgoing mail blocked on port 25.
  • Click the Change button and verify whether you have configured the server settings correctly.
  • Next, click the More Settings button at the bottom-left corner of the screen.
  • Move to the Advanced tab in the Internet Email Settings window.
  • In the Server Port Numbers section, change the existing outgoing server (SMTP) port 25 to <10025 or 26.
  • If necessary, you can also configure the secure server port settings.
  • Click the OK button to exit the Internet Email Settings window.
  • Click the Test Account Settings button to verify the configured server settings automatically.
  • Once verified, try sending a test email and check if the problem has been resolved.

Your ISP might block you from connecting to your mail server. However, it may also be caused by your local router or cable modem. To check if your router has blocked the SMTP port 25, follow these steps.

  • On your Windows 10 computer, click the Start menu and type ‘cmd’ in the search panel.
  • From the search result, give a right-click on the Command Prompt app and select Run as administrator.
  • In the Command Prompt window, type pkgmgr /iu:”TelnetClient” and hit the Enter key.
  • Wait until the telnet client is installed.
  • Now, close the Command Prompt app and relaunch it.
  • Type ‘telnet MAILSERVER 25’ in the Command Prompt window (replace MAILSERVER with your mail server (SMTP)) and press the Enter key.
  • If the SMTP port 25 has not been blocked, you do not need to fix anything.
  • If the port is being blocked, an error message will be displayed.
  • To fix this error, change the SMTP port.
  • If you have difficulties in resolving the outgoing mail blocked on port 25 issue, contact our technical support team for remote assistance.