Last year, we reported that Microsoft would start using "Clutter" to improve its Office 365 inbox experience. After having sorted over one million emails and saved users an average of 82 minutes a day, Microsoft is enabling the de-cluttering feature by default as part of its email experience for Office 365 users.
As mentioned previously, "Clutter" was a service introduced by Microsoft for Office 365. The service utilizes machine learning to help keep your inbox organized; Clutter can learn from the user and tailor the email inbox allowing for a more productive experience.
Starting June 1st, Clutter will be activated by default for those in the First Release program. This will be followed up by a release to standard participants on June 15th. With the mainstream release, Microsoft will also introduce administrative controls and status reports for Clutter. These reports will show you exactly how Clutter is organizing your email and inform you when new email is being moved. Although Clutter will be enabled by default, users will still have the ability to opt-out and disable the service on Outlook"s webpage, Outlook 2016 Preview, or clicking the the disable link at the bottom of each status report.
Source: Microsoft