Mailto Links Solved: I have searched, and tried every reported fix to the Firefox users issue with mailto links opening dozens & dozens of Internet Explorer widows, which forces a reboot to solve. Here’s how to solve it.
Install another desktop email client such as inky.com. After installing this eM Client mailto links worked. It would probably work with any email client. I believe it has to do with “prioritization” of the mailto default client. Somehow installing another email client will solve the issue!