Outlook for Mac email accounts not visible under Outlook preferences – need to delete duplicate accounts

Somehow I created a total of three Outlook email accounts (e.g. My Mail, My Mail 1, My Mail 2) all associated with the same email address; therefore, incoming email appears three times. I understand that I need to delete two of the accounts (My Mail 1, My Mail 2).

I went to 'Outlook Preferences' and selected 'Accounts' - no accounts are listed yet I continue to be able to send and receive emails.

Advice?

Thank you!