When a Microsoft Email account is hacked, the hackers often create rules that move new emails to a different folder so that you won't notice. You should reset the password, enable 2 factor authentication, log out existing sessions, delete these rules, and check your Deleted Items and Recover Deleted Items folder.
Links with more information: https://learn.microsoft.com/en-us/defender-office-365/responding-to-a-compromised-email-account?view=o365-worldwide Sign out of all locations: https://support.microsoft.com/en-us/account-billing/how-to-sign-out-of-your-microsoft-account-everywhere-58da4a74-a719-43a6-9dd0-74a7e613229f |