What to Know

  • Go to Menu > Preferences > Config Editor. Search for network.protocol-handler.warn-external.http.
  • Set values to True for network.protocol-handler.warn-external.http and .https.
  • Open a link in Thunderbird, select Choose, and pick a web browser. Check Always use this application.

This article explains how to change the default browser Thunderbird uses to open URLs. These instructions apply to Thunderbird 91.10, so update to the latest version before you begin.

Set the Default Browser in Thunderbird

Thunderbird usually passes the event off to your default web browser. Under normal circumstances, this all goes off without a hitch. However, if things go wrong, you need to know how to tell Thunderbird precisely which web browser you want it to use.

  1. Select Menu (the three lines) > Preferences.

    Menu icon and Preferences in Thunderbird

  2. Scroll down to the bottom of the Preferences window and select Config Editor.

    Config Editor in Thunderbird Preferences

  3. Select Show All to reveal the Config Editor settings.

    Show All in Thunderbird Config Editor

  4. Use the search at the top of the Config Editor window to look for network.protocol-handler.warn-external.http.

    Then, double-click network.protocol-handler.warn-external.http and network.protocol-handler.warn-external.https to set their values to True.

    network.protocol-handler.warn-external.http and true in Thunderbird

  5. Close the Config Editor, then open a link in an email. In the pop-up window, select Choose next to Choose other Application.

    Choose in Choose Application window in Thunderbird

  6. Find and select the application file for the browser you wish to make the default. For example, to choose Chrome in Windows, go to C: > Program Files > Google > Chrome > Application.

    Chrome inside Windows Explorer in Thunderbird

  7. Check the box next to Always use this application to open https/http links, then select Open Link.

    Checkbox and Open Link in Thunderbird

  8. Restart Thunderbird. If everything worked, Thunderbird will send clicks on URLs to whatever browser you selected.

This technique does not change your default web browser across all of your applications. This setting affects Thunderbird only.

Pro Tip

By following the steps above, you can set Thunderbird to use a web browser other than the default one the rest of your computer's applications use. It could be handy if you're concerned about viruses coming in through emails and only want to view these web pages in a high-security web browser.

And, you can handle HTTP-based URLs with one browser and HTTPS-based ones with another. Again, this could be something to consider for security and privacy issues. While you may trust your HTTPS (encrypted) requests to any of your installed web browsers, you may want your HTTP (non-encrypted) requests handled by a different browser.

To change which web browser to use in the future, go to Thunderbird Preferences and scroll down to the Files & Attachments section. Next to http and https, select the dropdown under Action to pick a new browser.

Action dropdown under Files & Attachments in Thunderbird Preferences

On Linux, this change should work on your particular distribution with your specific desktop environment.

Source