Outlook 365 and "New Outlook" - how do I stop it from automatically changing?

Dear JGreg7,

Good morning! Thank you for posting to the Microsoft Community. We are happy to help you.

Based on your description, I understand that you have a query "Outlook 365 and "New Outlook" - how do I stop it from automatically changing?"

To disable the New Outlook experience in Outlook 365, please try following these steps:

1. Open Outlook 365 and click on the "File" tab in the top left corner.
2. Click on "Options" in the left-hand menu.
3. In the Outlook Options window, click on "General" in the left-hand menu.
4. Scroll down to the "Start-up options" section and uncheck the box next to "Opt in to the New Outlook".
5. Click "OK" to save the changes.

This should prevent the New Outlook experience from automatically starting when you open Outlook 365. If you continue to experience issues, you can go to Windows Start and search for Outlook, you will see both Outlook, there is Outlook with PRE for the new Outlook in which you can open by olk.exe and the other Outlook for classic Outlook in which you can use Outlook.exe to open it.

However, if the "New outlook" button disappeared, try running Regedit.exe and go here (or the same with 15.0 if you don't have 16.0):

• HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Preferences
• And in this you will see UseNewOutlook
• Set it to 0, which means that running old Outlook actually runs it.

Additionally, you can use, HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\General

• REG_DWORD "HideNewOutlookToggle"
• Set to 0 (default) - The "Try the new Outlook" toggle, if available on the selected update channel, is displayed to users.
• Set to 1 - the "Try the new Outlook" toggle is hidden.

See Toggling out of the new Outlook for Windows preview - Microsoft Support

I hope the above information is helpful. Please feel free to let me know how it goes or if I got you wrong. If you still have any concerns, please let me know so I can provide more suggestions.