Set default mail client without adding mail account I'm on OSX el capitan (10.11.6).

I use outlook to access my email and would like outlook to be the default mail application. All the instructions I find online suggest that I should open mail and choose "Mail -> Preferences" to set the default mail app. Unfortunately Preferences is greyed out until an account is added. I don't have another account that I want to add to my mac.

How can I set the default mail client to Outlook without adding an account to the mail client?
I finally found something easy that worked, the SetDefaultMailApp from Microsoft: 

https://docs.microsoft.com/en-us/outlook/troubleshoot/outlook-for-mac/useful-tools#setdefaultmailapp