A recent update to Outlook has added the option to choose which browser to usen when clicking in on links in Outlook. Previously, clicking on links within Outlook would open the web page in the default browser set in Windows but this entry in Outlook is set to Microsoft Edge by default.
To get Outlook to use the one you have set as your default browser in Windows:
Click on Options under the File menu in Outlook
Click on the Advanced option
In the right pane, under Link Handling, set the option to “Open hyperlinks from Outlook in” to the Default Browser entry
Click OK
