How to archive mail in Outlook 2016 with a shortcut?
One could also do the following:


In the Outlook Menu Messages, look for the Move > option.  See if there is a Archive (provider) menu option.


Much like this:



That being the case, mapping a key to it can be done in the  Keyboard preferences.


Go to System Preferences
Select Keyboard
Select the Shortcuts tab
Click the Plus sign button and create an Application Specific shortcut.  (Preventing system wide use)
Type in the Menu option from Outlook exactly as it appears in the menu.
Type your preferred shortcut


Now, go back to Outlook and test it.