Is it because BT are "divorcing themselves off yahoo ? and some one has not told Yahoo seems that the tech bods are running amok AGAIN
I solved my problem, it was down to my spam filter - Peerblock - blocking the company providing the new mail service. once i allowed Critical path inc ,after finding this on a google search,
During the summer the BT Yahoo! portal will close, but existing customers will still be able to access their BT Yahoo! Mail account by clicking on a link from BT.com. Later in the year, existing customers will be moved to BT Mail. Your inbox, including all your folders, will be moved over and you will keep the same email address, although you may be prompted to change your password.
BT has chosen a company called Critical Path to provide the BT Mail new email service.
We will be contacting all of our BT Yahoo! customers in the coming months to tell you what to expect before your email is switched to the new service.
My windows mail worked again.