MC1338816 - New Outlook for Windows becomes available for GCC High and DoD

What and Why:

New Outlook for Windows will be available for U.S. Government clouds (GCC High and DoD sovereign environments). This milestone helps organizations move forward with adoption planning while maintaining administrative control.

Rollout Schedule:

• Public Preview (GCC High and DoD): New Outlook will begin Public Preview in July 2026.
• General Availability (GCC High, DoD):  We will begin rolling out in late September 2026 and expect to complete by late December 2026.
• General Availability (DoD): We will begin rolling out in late September 2026 and expect to complete by late December 2026.

Impact on Your Organization:

Who is affected:

• GCC High and DoD tenants
• Exchange and Outlook admins

Platforms/Services:

• New Outlook for Windows

What will happen:

• Existing users who continue to use classic Outlook for Windows are not affected.
• New Outlook for Windows becomes available for GCC High and DoD sovereign environments but remains OFF by default.
• New Outlook continues to be an opt-in experience. Users can choose to switch to the new experience and can revert back to classic Outlook at any time.
• This update does not change organization settings and will not automatically switch users from classic Outlook for Windows.
• Microsoft will provide at least 12 months’ notice before initiating any Microsoft-driven migration steps in managed environments.  Learn more about how we are approaching our migration timeline: New Outlook for Windows: A Guide to Product Availability.
• General Availability status enables organizations to begin evaluating and planning adoption timelines for the new Outlook experience.
• A future announcement will provide General Availability details for additional sovereign cloud environments.

Action Required / Recommendations:

Administrative action is required to enable new Outlook for Windows in supported sovereign environments. The experience remains off by default.

To enable new Outlook for Windows when it becomes available, set the appropriate registry key:

Enable availability when ready:

GCC High:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook
"NewOutlookForWindowsCloudType"=dword:00000003

DoD:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook 
      "NewOutlookForWindowsCloudType"=dword:00000004

Recommended actions:

• Control availability: Organizations retain control over new Outlook’s availability. Policies can be used to hide the toggle in classic Outlook for Windows, block new mailboxes from being added, or remove new Outlook from certain Windows builds. Refer to: Control the installation and use of new Outlook.
• Learn about policy management: Policies for new Outlook are managed through mailbox policies on the primary account, consistent with Outlook on the web. IT admins may choose to preconfigure an organization account as the primary account. Learn more: Policy Management – Deploy Office and Map Classic Outlook Policies to New Outlook.
• Prepare to manage updates: New Outlook introduces features through service-based flighting rather than build updates. Track new functionality using the Microsoft 365 Roadmap.
• Public Preview: Public Preview begins in July 2026 and provides an early look at new Outlook in U.S. Government environments. Set one of the registry keys listed above to access the Preview. 
•  Transition from COM to web add-ins: COM add-ins are not supported in new Outlook. Organizations should begin transitioning to web add-ins. Learn more: Migrate from COM to web add-ins.
• Plan for user migration: Microsoft will provide at least 12 months’ advance notice before Microsoft-driven migrations. Organizations are encouraged to plan and manage their own adoption timelines using the following resources:
  • Adoption and migration resources: New Microsoft Outlook for Windows
  • User training: Getting started with the new Outlook for Windows; Discover New Outlook for Windows – Training
  • Admin documentation: Overview of the new Outlook for Windows

We understand that some organizations may have specific requirements that prevent them from transitioning from classic Outlook at this time. New Outlook team welcomes feedback through the following channels:

• The Help tab in new Outlook for Windows (feedback must be enabled by tenant admin)
• Dialog boxes shown when a user reverts to classic Outlook
• Your Microsoft account team (for larger organizations)

Learn more:

• Feature comparison of the classic and new Outlook: New and classic Outlook for Windows feature comparison  
• Resources to help with change management and enterprise adoption: New Microsoft Outlook for Windows

Compliance considerations:

Area	Explanation
Alteration of existing customer data processing	New Outlook uses a service-based architecture aligned with Outlook on the web, which may change how policies are evaluated and applied compared to classic Outlook.
Admin controls available	Availability is controlled by registry keys and admin policies; the experience remains opt-in and OFF by default.
User self-enable/disable	Users can opt in to new Outlook when enabled by admin and revert back to classic Outlook at any time.