Updated May 8,July 28, 2025: We have updated the timeline below. Thank you for your patience.
content, timeline, and additional resources.
We are changing how you enable or disable the new Microsoft Outlookrecommended method for Windows and Microsoftdisabling Outlook for the web.web so that users can continue to access the new Outlook for Windows.
When this will happen:
General Availability (Worldwide, GCC):There is no change that is rolling out. We will begin rolling out late June 2025 (previously late April) and expecthave published a new support article with instructions on how to complete by mid-July 2025 (previously mid-May).use our existing infrastructure to block users from access Outlook for the web without impacting Outlook for Windows.
How this will affect your organization:
We're changingAdmins can follow the CASMailbox -OWAEnabled parameter that enables or disablesinstructions in this support article to block access to user mailboxes using Outlook for the web (formerly known as Outlook Web App or OWA) to block onlyusing Conditional Access. Blocking Outlook for the web and to not affect the behavior of newusing this policy has no impact on Outlook for Windows.
You can manage new Outlook for Windows with the CASMailbox-OneWinNativeOutlookEnabled policy.
You are receiving this message because our reporting indicates one or more users in your organization may be using the New Outlook for Windows.
Note: We will not change any existing value for the settings, but we will change which setting controls if the new Outlook for Windows is allowed for the user. Before this rollout, both CASMailbox-OWAEnabled and CASMailboxOneWinNativeOutlookEnabled policies are checked. After this rollout, we will remove the check for CASMailbox-OWAEnabled so you can have the chance to enable new Outlook and still disableOnce Outlook for the web if desired.is blocked, admins can set the CASMailbox policy -OWAEnabled to $true. This will have no impact on users' ability to access outlook for the web since the work was already done to block Outlook for the web with another policy.
What you need to do to prepare:
This rollout will happen automatically by the specified date withThere are no admin action required before the rollout. Review your current configurationchanges to determine the impact for your organization. You may wantexisting polices, so there is nothing you need to notify your admins about this change and update any relevant documentation.
do to prepare.
After this change takes effect, please confirm the CASMailbox OneWinNativeOutlookEnabled policy state for each mailbox. The default value is Enabled.
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