To disable Clutter in Office365 via Powershell, simply do the following:
Connect to Office365 Powershell for your account
Then simply run this command to disable Clutter for all mailboxes:
Get-Mailbox | Set-Clutter –enable $false
That’s it! If you want to disable Clutter for a single mailbox, you can do the following:
Set-clutter -identity email@example.com-Enable $false
To do this via the Office365 Portal, just navigate to: Mail > Automatic Processing > Clutter and turn it off!