Hello,

Microsoft introduced Office 365 groups a while back ago. This allows users to create groups them selves.That can be disturbing because they show up in your Global Address List. You can disable them for everyone with this line :

Set-OwaMailboxPolicy -Identity OwaMailboxPolicy-Default -GroupCreationEnabled $false

If you want to manage this permission more granular, user by user, you need to create a new OwaMailboxPolicy, and then assign it to the targeted users.

This settings, as the time of this article is written, can only be modified by PowerShell. You can see the current status of this setting with :

Get-OwaMailboxPolicy -Identity OwaMailboxPolicy-Default | Select-Object Name,GroupCreationEnabled

Note : To use those cmdlets, you need to be connected to Exchange Online.