Do you want to close the account or delete from you PC the two are different.
If removing from your pc go to tool email accounts highlight the bt account and delete.
This will stop any downloads of mail from the server.
To close your acount they will reduce it to a low level at first and after 3 months it should be deactivated.
How can I delete my btinternet email account?
Hi never sign in into the account it will be deactivated automatically.
Reply:Just sign out and forget about the accounts.