Using the New Outlook for Mac for personal email and calendar
When you look at the account settings, can you edit the incoming asnd outgoing servers? If not the account is added as a Microsoft cloud account. Remove the account from Outlook and add it back.
If you are to use it as a cloud account, if asked to remove it from all devices, say yes. Or, after entering the email address and Outlook finds it, click the link to add it as an IMAP account.