You need to first open Outlook at least once – otherwise the registry entrys are missing.

Close Outlook:

Powershell:
Set-ItemProperty -Path “HKCU:\SOFTWARE\Microsoft\Office\16.0\Outlook\setup” -Name ‘DisableOffice365SimplifiedAccountCreation’ -Value 1 -Type DWORD –Force

Open Outlook and add Account as manual server – Exchange Active-Sync  enter your server and your credentials and you’re done.

you can now even enable the „new“ mail-add-wizzard with

Powershell:
Set-ItemProperty -Path “HKCU:\SOFTWARE\Microsoft\Office\16.0\Outlook\setup” -Name ‘DisableOffice365SimplifiedAccountCreation’ -Value 0 -Type DWORD –Force