This is great! Is there a way to do it with the mailto client as well? I want to change the default mailto app from Mail to Outlook globally as an example but need relevance for it.
Edit (found it! for anyone else that may need it):
exists values whose (name of it as string = "ProgId" and it as string does not contain "Outlook") of keys "SOFTWARE\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice" of (user key of logged on user) of registry