my microsoft account has been changed to a different email address

You have the credentials to access the additional Exchange mailboxes if you don't have Full Access permission to them.

You have Full Access permission to the additional Exchange mailboxes.

Follow the instructions to recover your account.In Microsoft Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019 and Outlook for Microsoft 365, you can add multiple Microsoft Exchange accounts to the same profile if one of the following conditions is true: Select Forgot my password on the sign-in page, and then select I think someone else is using my Microsoft account. If that doesn't work, try to sign in to your account again. Starting with this step saves you extra effort if you accidentally signed in with a different account than the alert was for.

Try to reset your password with the instructions listed in When you can't sign in to your Microsoft account. Follow these steps to get back into your account: If you tried to sign in to your account but can't, someone may have changed your password. Create a strong password that you can remember, and don't share it with anybody else. If you think someone else may have accessed your account, go back to the Security basics page and select Change password. If it's in the Recent activity section, you can expand the activity and select Secure your account. If you see account activity that you're sure wasn't yours, let us know and we can help secure your account-if it's in the Unusual activity section, you can expand the activity and select This wasn't me. Select Review activity to check for any unusual sign-in attempts on the Recent activity page. Sign in to the Security basics page for your Microsoft account. If you received an email or text alerting you to an unusual sign-in attempt on your account but you haven't done anything different with your account recently, follow these steps to review your account security:

My microsoft account has been changed to a different email address