First, connect to Office365 / Exchange via PowerShell.
http://iterrors.com/connect-to-office-365-using-windows-powershell/
To turn Clutter on:
Get-Mailbox | Set-Clutter -Enable $true
To turn Clutter off:
Get-Mailbox | Set-Clutter -Enable $false
To see if it worked, you can get the Clutter status by typing:
Get-Clutter -Identity info@iterrors.com