To verify you're experiencing this issue, use Microsoft Remote Connectivity Analyzer to test the Outlook Autodiscover process, and then search the text in the test results for the 'IMAP' text string. However, because Outlook receives a successful Autodiscover response that has IMAP settings, it marks the account as a non-Microsoft 365 account, and then stores the Autodiscover URL as the Last Known Good URL in the profile.

This issue occurs because the Autodiscover process that's used by Outlook did not retrieve the XML from Microsoft 365, and received an unexpected result from a third-party web server that uses IMAP settings from either or Typically in this situation, the lookup fails and Outlook eventually performs an Autodiscover lookup against. Additionally, the option on the View tab to turn on or off the Focused Inbox also disappears. When you switch from the Inbox to other folders, such as the Sent Items folder, and then you return to Inbox, the Focused Inbox option disappears. You set up a Microsoft 365 account in Microsoft Outlook.

Focused inbox disappeared