As most administrators are aware the clutter feature of Office 365 has been automatically enabled within their tenants. End users manage the clutter feature through Outlook Web Access. For example - https://support.office.com/en-us/article/Turn-off-Clutter-in-Outlook-a9c72a77-1bc4-40e6-ba6d-103c1d1aba4c?ui=en-US&rs=en-US&ad=US
Recently a customer presented with a tenant where clutter was not automatically enabled for them. The users were not recently migrated, had well over 1,000 items so initial usage patterns could be analyzed, yet reviewing get-clutter showed the option as disabled.
PS C:\> Get-Clutter -Identity ALIAS
RunspaceId : e1028943-b6dd-44b6-ae1e-36fc1f6aea67
IsEnabled : False
MailboxIdentity : CN=Tim McMichael,OU=domain.onmicrosoft.com,OU=Microsoft Exchange Hosted
IsValid : True
ObjectState : New
Initially we believed that an anomaly had occurred and that a tenant was missed in the enablement process. When reviewing the situation further – we noted that Outlook Web Access was disabled on the users.
PS C:\> Get-CASMailbox ALIAS | Fl name,OwaEnabled
Name : Tim McMichael
OWAEnabled : FALSE
When Outlook Web Access is disabled – the end user has no ability to manage the clutter service. OWA is the only interface to access the clutter settings of a mailbox by the end user. If OWA is disabled at the time that clutter would have normally been automatically enabled we will not enable clutter. If OWA is disabled after clutter has been enabled we will not disable clutter.
With OWA access being blocked, and the user being prevented from managing this setting themselves, the decision was made to not automatically enable clutter in this scenario.