Make this entry for the windows user to stop looking at Office 365 exchange when trying to use Simplicity Hosted Exchange.
1. Close Outlook, then open up a program called Registry Editor by pressing the windows icon and typing in simply regedit.
2. Navigate using the arrows on the left-hand side to the following location:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
3. You'll want to now select the Autodiscover folder, and right-click on the empty space in the right-hand side to create a new DWORD key - the property should be ExcludeExplicitO365Endpoint set to a value of 1.
4. Reboot the computer.
5. The fix should now be applied, next time you open Outlook it should take this into account and not query Office365 for the autodiscover process, and simply set up the hosted exchange mailbox instead.