Outlook automatically links to Microsoft Edge

Firefox is my default browser. Up until a few months ago, if I clicked a link in an Outlook email, it took me to Firefox and opened the site. Now it takes me to Microsoft Edge. At the same time, another problem arose, albeit minor. When I am using Firefox and attempt to email a link, there is a message, "Navigation failed" and a blank screen appears. This is not a big problem, since when I open Outlook the email is waiting to be sent. But this too smacks of something Microsoft is doing to sabotage the competition. Thanks, Bob Katz Bob@VRA-Rehab.ca