I logged-in to the bt email page this morning (19th Sept) as I usually do each morning, and saw a notice that the email login is changing. I tried the new login (bt.com/email) and it didn't work, leaving me on a blank page ( https://email.bt.com/mail/sso/engine.jsp). I tried the old login and that didn't work either, leaving me on the same blank page. I tried a few other ideas, like clicking on "email" in the MyBT homepahe, but nothing worked. Eventually I succeeded, although I don't know how, with https://email.bt.com/mail/index-rui.jsp so I quickly saved that as a bookmark.
Something seems to have gone wrong! Maybe the new login method has not gone live yet and I have screwed it up by trying too soon.
Peter M