Some versions of Microsoft Outlook 2016 feature “Simplified Account Creation” which does not allow for configuration of mailboxes using Exchange ActiveSync (EAS). Fortunately, the “Simplified Account Creation” can be disabled in these releases of Outlook 2016 by making a registry change on the affected computer(s).
Microsoft has provided step by step instructions how to disable Simplified Account Creation.
After following these instructions, open Outlook 2016 and you will see the traditional account dialog box to add your account(s).