Microsoft has removed Clutter in Outlook 2019/O365 and Outlook for the Web. It has been replaced by Focused Inbox.
To disable Clutter in Outlook 2016 or earlier, follow the steps below.
- In Outlook, right-click the Clutter folder and the select Manage Clutter. (If you don't see the Manage Clutter option, you may be using Focused Inbox now).
Either uncheck the box Separate items identified as Clutter or select the option Don't separate items identified as Clutter depending on which option you see on the Clutter options page.
- Click Save to turn off Clutter.