Using Classic Outlook on Windows for personal email, calendar, and contact management
Ditto to what's been said already...and...this was a problem with the MAC New Outlook rollout back in October of 2020. It's been solved for MAC users, albeit not satisfactorily: https://answers.microsoft.com/en-us/outlook_com/forum/all/inbox-email-count-in-new-outlook-for-mac/4b1d2cd7-1978-4a6c-9480-bf2706812300