The BT email url has changed for me this morning, and by the looks of it has changed for you, bigbilly.
If you follow an old bookmark it directs you to a page with a new link, which doesn't always work.
This link works for me though: https://ux.btmail.bt.com/cp/index-rui.jsp?v=126.96.36.199#app/mail
An alternative is to sign in to "MyBT" and get to mail from there.
I've tried the new links and they don't work. I have to login via MyBT then click Email every time I want to do something or read a new message - it's not fit for purpose.
Try clearing your browsers cache/cookies and history then use the links as suggested.
More accurately, why do I have to come here to find out how to gain access?
How do you normally log onto your email account and where else have you tried to find out how to gain access?
Well, that's weird.
My old bookmark now works again, whereas it didn't this morning (15th November).
AND the new bookmark still works.
I call that a win.
That looks like the answer. It does redirect after a while but suggests that you set up the new URL. I was nervous by the new URL as I get lots of scam emails telling me that my email will be shut down if I don't send my log in details supposedly sent from BT.