This new feature was just released, and I didn’t feel I wanted a system to pre-sort my email. I have too many devices that get my email and it was not a feature I felt would be of benefit to me.
You will need to log into Office 365 Sign-in page https://outlook.office365.com
Select the Option cogwheel (top right) -> Options (drop down right), -> Mail (left hand side)
Clutter -> Don’t Separate -> SAVE