To get there to make the setting change: I've been experiencing the "can't delete IMAPS email" but you describe.
This solutions applies for following version of Microsoft Outlook: Step 1: Temporarily Disable any installed 3rd Party Antivirus: Some times Antivirus/Malware/Adware programs mark Microsoft office installer files as Spam and block it from installing.
Until then, there are still plenty of new features in Outlook 2016 to use and discover.
As mentioned, during the main lifespan of Outlook 2013, various new features and changes have been introduced as well.
Please refer your vendors website for disabling it temporarily.
Once installation is done you can activate it again.