Learn to Fix the “Connection to Server Timed Out Error” in Thunderbird

Megha Sharma
Megha Sharma linkedin | Updated On - February 28, 2022 |

Read time 5 minutes

This blog discusses a common Thunderbird error, “Connection to server timed out,” providing the best ways to handle it.

About the Thunderbird “Connection to Server Timed Out” Error

Most of the Thunderbird email client users are aware of the “Connection to server timed out” error which is encountered when an attempt to send or receive an email is made. It happens mostly with large emails or emails with large-sized attachments. It could be displayed with this information.

Send Message Error
Sending of the message failed.
The message could not be sent because the connection to Outgoing server (SMTP) smtp.gmail.com timed out. Try again.


Send Message Error
Sending of the message failed.
The message could not be sent because the connection to Outgoing server (SMTP) smtp.gmail.com timed out. Try again or contact your network administrator.

Both errors represent similar issues where the email fails to send because the server has taken much time to respond to the sending request and the server time is out. Active connection to Thunderbird fails while downloading email to it.

Causes of the Thunderbird “Connection to Server Timed Out” Error
  • Incorrect account configuration (SMTP port) settings
  • Email blockage due to programs like Windows Firewall, Antivirus, etc.
  • SSL/TLS Server setting is not configured
  • Spam detected on Port 25 by Internet Service Provider
  • Server Timeout is set to a low value
Solutions to the Thunderbird “Connection to Server Timed Out” Error

After knowing about the Connection timed out error and the common reasons responsible for it, one should proceed to its solutions as under.

  • Disable Antivirus, Firewall, etc.
    Blocking of messages in Thunderbird email client due to the Connection to server timed out error is rarely linked with third-party antivirus applications and Windows Firewall on the system. Still, users can try to disable both and check if emails can be sent and received via the Thunderbird email client.

    Go to the Windows Firewall option in the Control Panel on your system. Click on the Turn Windows Firewall on or off from the left panel. Next, select the second Turn off Windows Firewall for your network and click OK.

  • Check the Outgoing Server (SMTP) Settings
    Follow the given process to check and correct the account configuration settings of the Outgoing Server (SMTP) in your Thunderbird email client.

    1. Open your Thunderbird email client application.
    2. Navigate to Tools > Accounts.
    3. Now, click on the Outgoing Server (SMTP) tab and check the details for user name, Port, Secure Authentication, Connection Security Settings, etc. Click the Edit option to change any setting which you know is incorrect currently. Ensure that Connection Security Settings for SMTP are set to STARTTLS.
    4. Restart the email client and try sending emails.
  • Increase the Server Timeout Value
    As the error itself indicates that the connection to the server is timed out, it would be helpful to increase the server timeout value manually. Here is the procedure to do this.

    1. Open the Thunderbird application on your system.
    2. Navigate to Tools > Options > Advanced > General > Config Editor.
    3. Go to the search file, type mailnews.tcptimeout and press Enter.
    4. Right-click on the search result mailnews.tcptimeout and select the Modify option from the drop-down list.
    5. Now, edit the value to provide a higher value and save it.
    6. Restart the Thunderbird email client and try sending emails now.

These were the fixes that can save you from the Thunderbird “Connection to server timed out” error and let you send or receive emails without error messages.

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