Clutter is Microsoft's new mail filter introduced in 2016


As new email comes in, it takes messages you're most likely to ignore and puts them into the "Clutter" folder.


To disable this feature, login to https://login.microsoftonline.com


At the top left corner of the page, select the App launcher icon, and then select Mail.


Outlook on the web App Launcher


Click the Gear icon and Select Options



From the Options list select Clutter



Uncheck "Separate items identified as clutter" then click Save