In June we announced updates to the Office 365 user experience, including a simpler and more powerful Outlook on the web, which would show up later in the summer. Starting September 10th, we’ll roll out an opt-in toggle so users in Targeted Release can try this early version of the new web experience. Users who try this early version of the new Outlook on the web can go back to the classic experience as often as they want.
Users who are in Targeted Release will see “Try the new Outlook” next to the toggle and can opt in (and out) of the trial as often as they want. However, we also want to ensure that admins can control whether their users see this toggle.
If you’re an Office 365 admin and you don’t want your users to have access to the opt-in toggle, you need to complete the following steps prior to September 10th, 2018:
1) Connect to Exchange Online PowerShell.
2) Review the OWA mailbox policies that have been created previously. To do this, run Get-OwaMailboxPolicy.
3) This will output all the policies that have been created. If you have multiple policies, you will want to adjust each policy that you want to block the new experience opt-in toggle.
4) Most tenants will have a single policy, and they should run the following command to turn off the toggle: