https://groups.io/g/office-accessibility/topic/99025717

Getting back to Outlook Classic User Interface if you’re in the Inaccessible New Outlook User Interface (AKA Outlook Preview or Outlook PRE)
To change back to the Outlook Classic user interface from the New Outlook user interface:

Note:  The New Outlook interface is NOT accessible and most of the keyboard shortcuts you are accustomed to are not available.

1. Hit F6 until you hear, “Ribbon Region, Tab Control, Home Tab Selected, one of three.”  (Or something very similar.)

2. Hit Tab once, and you should land on the control for toggling out of New Outlook.  NVDA Announces the following when you land on the toggle, “Try the New Outlook, Toggle Switch, On. Press Enter to go back to the classic Outlook for Windows.”  There is a bit more verbiage after this, but once you hear you’re on that toggle switch, activate it with Enter.

In the case of going back to Classic from New, prior to Outlook doing so you will be presented with a Feedback form that I’d encourage you to fill out, and blast Microsoft about the appalling lack of accessibility in this UI.  If you choose to fill out the survey, at the end there are two buttons:  Submit (active if and only if you have filled out the survey) and Skip Feedback.  Whether you’ve filled out the survey or not, hit tab, slowly (this dialog is sluggish and it’s easy to circle around if you’re not patient between each hit of tab and listen for what you’ve landed on) until you land on the button that’s appropriate to what you’re doing, and activate it.  If you happen to circle back to the close button for the survey dialog, just activate it.

In order to achieve the change of User Interface, Outlook must close and start up again to complete that transition.

After you’ve dealt with that dialog in whatever way you saw fit, that’s when Outlook will close and restart, and when it does you are back in Outlook classic.  Be aware that if you are in the Classic view, ALT + T will activate the toggle that takes you back to New View.

—
Brian – Virginia, USA – Windows 11 Pro, 64-Bit, Version 22H2, Build 22621; Office 2016, (Version 2304, Build 16.0.16327.20200) 32-bit; Android 13 (MIUI 14)

There are many people who can only make themselves feel better about themselves by making themselves feel better than others.

    ~ Commenter Looking_in on the Washington Post, 7/10/2014