My apologies, I see that you were using the Windows Live Mail client that shipped with Windows 7. In that case the same settings that you used in Live Mail should work in Outlook but as you mentioned, they do not. Have you checked them against this page:
https://www.bt.com/help/email/manage...-email-servers ?
Apologies if I'm asking for the stuff that you've already checked but in that case the actual error may be unclear to me. What is the actual error that you get when you try to send an e-mail?