In September 2014, Office 365 announced the “first phase of Groups in Office 365”. Although Groups already existed, this heralded a new collaboration tool that would be universally accessible from Outlook, Lync and SharePoint environments including Yammer. These groups, by default, can be created by normal users.
However, not all Office 365 administrators are delighted with the thought of users provisioning groups and may want to limit this functionality. The ability to create groups (or not) is controlled with OWA Mailbox Policies. Currently, the option to disable this is not in the GUI, so needs to be done using PowerShell. The Syntax to disable collaboration group creation is:
Set-OWAMailboxPolicy –Identity <ID> -GroupCreationEnabled $false