Windows 10 default Mail application is set to Microsoft Mail. To change it so that when you click on an email link in Outlook, it opens in Outlook, do the following:
- In the search field (next to start button on task bar) type Default
- Open the Default App Settings window
- Under Email, it needs to say Outlook. If it says anything else, click on the work and choose Outlook from the dropdown list
- Close the window
Now when you click a link an email now, it should open a new message in Outlook.