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As Microsoft transitions to actively promoting the new Outlook with an opt-out approach rather than opt-in, organizations may need to control or prevent this migration. This guide outlines methods to manage the new Outlook deployment.

Implementation strategies

Before implementing specific controls, consider which strategy best fits your organization’s needs:

Complete prevention

Follow these steps in order:

  1. Block installation (Step 3)
  2. Hide the toggle (Step 1)
  3. Disable Exchange access (Step 4)

Controlled migration

Follow these steps:

  1. Configure migration timing (Step 2) with custom intervals:
  2. 0: Never prompt users
  3. 1: Prompt on every launch
  4. 2-9999: Days between prompts
  5. Optionally hide the toggle (Step 1) if you don’t want manual switching

Toggle-only control

  1. Only implement Step 1 to hide the manual toggle
  2. Leave all other settings unchanged for future automated migration

Important considerations

  1. Exchange integration: New Outlook isn’t supported for on-premises environments. For hybrid environments, only target Microsoft 365 users.
  2. Windows updates: Starting January 2025, Windows updates will include the new Outlook. Plan your prevention strategy accordingly.
  3. Mail app deprecation: Windows Mail and Calendar apps ended support on December 31, 2024. Consider this when planning your migration strategy.
  4. Policy layering: The controls below work at different levels (client, mailbox, organization) and can be combined based on your needs.

Step 1: Control the toggle visibility

This method controls visibility of the toggle button in classic Outlook.

For Microsoft 365 administrators

Configure through Microsoft 365 Apps admin center:

  1. Sign in to Microsoft 365 Apps admin center
  2. Navigate to Customization > Policy Management
  3. Click Create to set up a new cloud policy
  4. Search for “Hide the ‘Try the new Outlook’ toggle in Outlook” and enable it

For regular users

Apply these registry settings:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\General]

"HideNewOutlookToggle"=dword:00000000

Step 2: Manage automatic migration

This method controls Microsoft’s automatic migration attempts, separate from the toggle visibility.

Configure migration settings

Apply these registry settings:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\General]

"DoNewOutlookAutoMigration"=dword:00000000

"NewOutlookAutoMigrationRetryIntervals"=dword:00000000

Note: While not setting NewOutlookAutoMigrationRetryIntervals currently has the same effect as setting it to 0, we recommend explicitly setting it to ensure the policy remains effective if default behaviors change.

Step 3: Block installation

For Windows 11 (Build 23H2 and later)

While you cannot prevent the initial installation, you can remove the new Outlook app using PowerShell:

Remove-AppxProvisionedPackage -AllUsers -Online -PackageName (Get-AppxPackage Microsoft.OutlookForWindows).PackageFullName

Additionally, remove the Windows orchestrator registry value:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsUpdate\Orchestrator\UScheduler_Oobe\OutlookUpdate

For Windows 10

To prevent the automatic installation (starting January 28, 2025):

  1. Add the registry key:
 HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsUpdate\Orchestrator\UScheduler_Oobe
  1. Create a REG_SZ value named BlockedOobeUpdaters with the value [“MS_Outlook”] (including brackets)
  2. If already installed, remove using PowerShell:
Remove-AppxProvisionedPackage -AllUsers -Online -PackageName (Get-AppxPackage Microsoft.OutlookForWindows).PackageFullName

Step 4: Control Exchange access

Use Exchange PowerShell to prevent mailbox access to the new Outlook:

For individual mailboxes

Set-CASMailbox -Identity user@domain.com -OneWinNativeOutlookEnabled $false

For all organization mailboxes

Get-OwaMailboxPolicy | Set-OwaMailboxPolicy -OneWinNativeOutlookEnabled $false

To re-enable access later:

Get-OwaMailboxPolicy | Set-OwaMailboxPolicy -OneWinNativeOutlookEnabled $true

Keep monitoring Microsoft’s announcements as these controls may evolve with the new Outlook rollout.

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