I know the title of this post may sound blasphemous!!! How dare you use a Microsoft program as a default on a MacBook...SHAME!!
What happens is when you click an email link on the Mac it defaults to opening the Mac email app, by doing the following it will open up Outlook.
Now I know you are going to ask, why don't I configure the email program that comes with the Mac with our Exchange mail server?? My only answer I guess is that my staff is brand loyal? Any way here is how you do it.