Disable 365 on Outlook 2019 (Autodiscover Exchange)

At first create a new GPO.

Edit the GPO and go to Usersettings / Settings / Windows-Settings

ADD a new Registering with the following settings

• Struktur: HKEY_CURRENT_USER
• Schlüsselpfad: SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover
• Name: ExcludeExplicitO365Endpoint
  
• Werttyp: REG_DWORD
• Wertedaten: 00000001

Done