Can you close all programs
Press the windows key + X and click on Control Panel.
Type in the top right Mail and click on Mail
Click Show Profiles
Then Add a new profile and enter in your BTInternet details.
Once done, set this new profile as your default profile from the dropdown box there.
Then open Outlook and tell me how it now functions.
I can also do these steps for you, and have made a request via Additional Services. This is optional, and if you choose to do this, I can, with your permission, remote into your computer while you watch and do all these steps (and deal with any problems that arise during them) for you. Or if you do not choose to take this service, we can continue here. This is no problem at all. Just let me know please.
Else let me know the results please