Outlook connecting to Office365 instead of on-premise Exchange server

"HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover" the DWORD (32-bit)Value with the name ExcludeExplicitO365EndPoint and gave it the value 1.

ODER

Key: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
Value: EnableOffice365ConfigService
Default: 0
Data: Set this DWORD data to 1 to force Outlook to call the Office 365 Config Service to retrieve appropriate Autodiscover URLs.