If this doesn't apply to your environment, Please see this Microsoft Support article and reply with what platform (Windows, Mac, Android, iOS) and version of Outlook you are using.

What version of Outlook do I have? - Microsoft Support

Or if you access Outlook On the Web (Sign in to your Microsoft account) via a browser, what platform (Windows, Mac, Android, iOS) and browser (Chrome, Edge. Safari, Firefox) you are using.