People need a simple – but accurate – way to manage the high volume of email messages they receive. There should be a way to separate out unimportant items from important ones without having to set up and manage large numbers of inbox rules… which can get complicated very quickly.

This is the core goal of “clutter,” the codename for a new feature in Outlook Web App in Office 365. At its heart, it intends to remove as much unimportant mail, or clutter, from a user’s inbox as possible so that a user’s inbox can, well, become their inbox again.Microsoft Explains About the Evolution of Email and "Clutter" [blogs.office.com]