Focused Inbox has replaced the Clutter folder. Focused Inbox separates your inbox into two tabs—Focused and Other. Your most important email messages are on the Focused tab while the rest remain easily accessible—but out of the way—on the Other tab.
Notes:
In Outlook for Windows, Focused Inbox is available only for Microsoft 365, Exchange, and Outlook.com accounts.
If you don't see Focused and Other in your mailbox, you might have a Clutter folder instead. For more information, see Use Clutter to sort low-priority messages in Outlook.
The Focused Inbox REST API provides Microsoft 365 mailbox message classification and training to help users sort their email efficiently. However, this API isn't supported for the Microsoft 365 Shared mailbox. Outlook for Windows currently displays "Focused Inbox" hints for shared mailboxes. This is unexpected behavior. Microsoft is aware of the problem, and this article will be updated after changes are complete.
Turn Focused Inbox on
How do I turn off Focused Inbox?