Outlook / Exchange Authentication Issue – Troubleshooting Required

Issue Summary: User is on Exchange On-Premises using Outlook Classic. User also has a Microsoft account using the same email address. After setting up Outlook on a new computer, Microsoft login prompts appeared. We bypassed the Microsoft account sign-in, but Outlook now repeatedly prompts the user to enter their password.

Mailbox access is intermittent due to continuous credential prompts.

Requirements

Exchange On-Premises administration Outlook Classic troubleshooting Windows credential management Microsoft account and Office authentication troubleshooting Autodiscover and profile configuration Please provide your experience with similar Outlook/Exchange authentication issues and your estimated time to resolve.