The new Mail App does not support pop3 or IMAP only EAS. There are options, the primary MS one being to set up Outlook.com account and use that to collect mail from pop3 mailboxes.
This however brings up issues of the reply to address etc. As the BT Connect mail server is Exchange based are there any other options to directly connect the Mail App.
Windows 8 is dire and I sincerly hope it dies quickly but I am going to have to support it so need to prove each app.