Problem

Microsoft introduced the new Outlook last year, a web-based application designed to replace both the built-in Outlook in Windows 11 and the classic Outlook in Microsoft 365. However, many users, including myself, are not fond of the new Outlook.

In early 2025, I discovered that Microsoft plans to automatically install the new Outlook on new Windows 11 machines. Additionally, users will be forced to switch to the new Outlook after opening the classic Outlook app a few times. What’s even more frustrating is that even if you uninstall the new Outlook app, it will reappear after some time. Microsoft is essentially forcing users to adopt the new Outlook, regardless of their preferences, and this has been a source of frustration for me.

In this blog post, I’ll share a method to disable this automatic upgrade behavior. Hopefully, this solution will allow you to avoid the new Outlook for an extended period without being repeatedly inconvenienced.

Solution

1. Uninstall the new Outlook App

Close all Outlook instances, and go to Settings - Apps - Installed apps, and uninstall the new Outlook if it's present.

2. Edit Registry

Press Windows Key + R and run regedit

Go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\General

  • Add a 32-bit DWORD with name HideNewOutlookToggle and value of 1
  • Delete NewOutlookAutoMigrationStage
  • Delete NewOutlookAutoMigrationType

Delete the entire \HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\NewOutlook key

Go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences

  • Add a 32-bit DWORD with name UseNewOutlook and value of 0
  • Delete NewOutlookRenudgeStartDate
  • Delete NewOutlookRenudgeWatermark

3. Restart computer and classic Outlook

Finally, restart your computer and then open the classic outlook that you liked for 30 years.

Now, the "Use new Outlook" switch is completely gone, and you won't be forced to use the new Outlook next time you start the classic Outlook!