In November 2014 Microsoft quietly added a new feature for its Office 365 users called Clutter. But what is it and what does it do? Clutter is designed to move low priority emails into a folder called Clutter meaning your inbox is less (excuse the pun) cluttered. The feature looks at your email reading habits to work out what you would view as a low priority (newsletters or mass email sendouts, perhaps) and then moves it to your Clutter folder.
However, you can speed up the process of learning by marking certain emails as clutter, and then Outlook will know for next time. To do this, simply right click on the email and select "Move to Clutter". This also works the other way around too, so you can prevent emails going AWOL by telling Outlook what isn't clutter. Simply head to the Clutter folder and right click on an email and select "Move to Inbox".
At the moment Clutter is available through the O365 OWA page and should be managed through Outlook 2016.