You can update the email address accounts@xx.xx to olduser@xx.xx. Then once this email has been updated, invite accounts@xx.xx in as a user to the organisation again and set up this account when you accept the invite.
By doing this, any transactions created by the old user will be associated with this old account and will show this way in the History and notes, while any new transactions created by accounts@xx.xx will then show under the new user.
You can update the email address accounts@xx.xx to olduser@xx.xx. Then once this email has been updated, invite accounts@xx.xx in as a user to the organisation again and set up this account when you accept the invite.
By doing this, any transactions created by the old user will be associated with this old account and will show this way in the History and notes, while any new transactions created by accounts@xx.xx will then show under the new user.
The old user account can then be deleted.