Outlook still syncing removed accounts

I am using outlook within office 2021 on windows 11.

I have been monitoring a mailbox for a charity, but this is no longer required.

I removed the account, and it is no longer shown in outlook, nor in outlook in control panel.

However as i started to remove folders i realised it is still syncing .

How do i remove all of the data (old e-mails and folders) without these syncing to the O365 exchange server.