Sending, receiving, and organizing email in Outlook.com
Go to https://outlook.office365.com/mail/ and check if that is your business mail.
In outlook classic, click on File, Account settings, then select Account settings. Is there one account in the list?
Go to admin.microsoft.com click on Users, Active Users. Find your email and click on it. Click on Manage username and email. What address is listed as your primary email address and username?