Outlook with on premises Exchange prompting for Microsoft online logon

I have two workstations unable to stay connected to Exchange. This is an on premises domain and Exchange server.

Users are presented with a Microsoft online logon dialog on start-up. Closing the dialog connected to Exchange to "Needs Password".

The dialog is pre-populated with [email protected]. Clicking next results in "This account isn't on our system" (it's a local domain, local exchange and nothing to do with Microsoft online).

What am I supposed to do about this?

What is the correct way to connect to their local Exchange account without Outlook prompting for a non-existent Microsoft online account?

Follow the steps to create the ExcludeExplicitO365Endpoint registry value to bypass connection to O365.

1. Press win+r, then type regedit on the outlook client.

2. Find or create the below registry key.

HKCU\Software \Microsoft\Office\16.0\Outlook\AutoDiscover

3. Create a new DWORD registry value ExcludeExplicitO365Endpoint with a value of 1 , and restart Outlook.