How to truly change the default email client in Windows 10

Have you encountered installing Microsoft Outlook in your fresh Windows 10 install, only to find it too resource hog for your use case, and thus installing Thunderbird, Mailbird, or any other email client that’s a lot less load to your computer’s meager resources?

Of course, you changed your system settings so that the default email app will be your new email client, just as below:

Apparently, this settings only affects clicks on MAILTO links. Continue reading