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.
But then, when you hit the send in email button in your favorite spreadsheet or document program, just as the one below:
Or perhaps, you’re trying to send a file by email from the File Explorer context menu as follows:
Microsoft Outlook reopens and tries to attach the file you’re trying to send in a new message.
Clearly, the settings isn’t enough. That’s why you need to manually edit the registry:
And go to:
Double click the (Default) in the right window, and change both Value data to your preferred app name, as follows:
Voila! I hope everything works for you now, just as it did in mine.