To return to the classic view of Outlook from the new Outlook, you can use the toggle switch available in the new Outlook interface. If you do not see the toggle, it may be due to several reasons such as unsupported Windows versions, unsupported Outlook versions, or account types.
If the toggle is visible but unresponsive, it could indicate installation issues related to security settings. In such cases, you may need to resolve those installation issues first.
If you are unable to access the toggle at all, ensure that your Windows version is supported (Windows 10, Build 1809 or higher) and that you are using a compatible Outlook version (not a nonsubscription version like Outlook 2021 or 2019). Additionally, check if there are any group policies or registry settings that might be hiding the toggle.
For more detailed steps, you may want to refer to the Microsoft documentation on resolving deployment issues in Outlook.