New Outlook Is Now Generally Available for GCC High and DoD

New Outlook for Windows is now generally available for GCC High and DoD environments, according to Microsoft 365 Message Center ID MC1338816.

Microsoft began general availability on September 30, 2026, after launching the public preview on July 30. The company expects to complete the rollout by the end of 2026.

New Outlook remains opt-in for GCC High and DoD

Microsoft is not automatically moving government customers from classic Outlook to New Outlook.

New Outlook remains off by default and opt-in, which means users and organizations must choose to enable it. Users can also switch back to classic Outlook at any time.

The general availability rollout does not change existing classic Outlook installations or current organizational settings.

Microsoft recommends that organizations start evaluating their adoption timelines and prepare for the transition by moving COM add-ins to web add-ins where possible.

Microsoft promises at least 12 months’ notice before migration changes

Microsoft has not announced a forced migration timeline for GCC High or DoD customers.

The company says administrators will receive at least 12 months’ notice before it introduces any future migration steps.

Administrators can also control New Outlook availability through organizational policies and registry settings.

Admins can enable New Outlook through the registry

Microsoft has shared registry settings that administrators can use to enable New Outlook in GCC High and DoD environments.

For GCC High, administrators need to set NewOutlookForWindowsCloudType to 3 under the Outlook policy registry path.

For DoD, administrators need to set the same registry value to 4.

The settings give organizations additional control over when users can start testing or adopting the new client.

The expansion comes as Microsoft continues making other changes across Outlook. The company is cutting off MSIX attachments over security risks, while a separate issue has broken classic Outlook search for shared mailboxes.

Microsoft is also preparing a conversational Copilot upgrade for Outlook on the web that will help users draft, edit, and format emails.

Via Neowin