https://support.microsoft.com/en-us/office/focused-inbox-for-outlook-f445ad7f-02f4-4294-a82e-71d8964e3978
For the Old Outlook
Turn Focused Inbox OFF in classic Outlook
1. In Outlook, select the View tab.
2. Unselect Show Focused Inbox.
Turn Focused Inbox ON in classic Outlook
1. In Outlook, select the View tab.
2. Select Show Focused Inbox.
For the new Outlook
Turn Focused Inbox ON or OFF in new Outlook
1. Open Outlook.
2. Select View > View Settings⚙️.
3. In Mail > Layout, select the account you want to apply the settings to.
• To turn it on - Select the option Sort messages into Focused and Other
• To turn it off - Select the option Don't sort my messages.
4. Select Save if you made any changes.