Clutter is a great capability to ensure the most important messages appear in your inbox and it uses machine learning and behavioral patterns to redirect other messages into a Clutter folder. You can opt out of that experience or just the daily emails sent to you via Clutter.
To opt-out, you just open Outlook on the web and click on the Settings gear in the upper right corner
Then click on "Mail" in the right lower corner of your screen and "Clutter" in the left upper side.
Then uncheck the either the daily email or Clutter capability, or both. Be sure to click "Save" when finished.
Of course you can turn Clutter features back on later if you find your Inbox filling with clutter.