Microsoft replacing windows Mail with a new Outlook app. It is built using the same scripts as Outlook on the web, but in an app framework. It supports multiple accounts, currently only Outlook.com, Microsoft 365 Work or School, and IMAP accounts. Microsoft 365 Work or School accounts must have a Microsoft 365 software subscription on their account to use new Outlook for Windows or new Outlook for Mac.
Reset the New Outlook Profile
When you switch on the new Outlook, it pulls accounts in from your Outlook desktop profile. I'll show you how to clear the profile and create a new profile.