Have a look at this thread and try as suggested in it.
On Firefox I got round the problem by opening a 'private window' and accessing email acount via that, perhaps your browser has a similar facility?
@ijevans wrote:
what is it in the link that is different to what I've already told you i tried? I have deleted history and cache, restarted laptop. Whenever I go to the bt email login page it takes me straight into email inbox bypassing login page. I've had btemail for over 25 years, not a single problem, but now youve changed it I'm having multiple issues. It appears its happening to many users? please help
First off, I have not made any changes, I do not work for BT. I am a customer just like you!
As regards what is different, When you are using your browser both Edge and Chrome continue running processes in the back ground even after you close them, also by default Edge launches as a back ground process during Windows start up. I have never check with Chrome but I suspect it probably will be the same as Edge is Chrome based.
By stopping them in the Task Manager it means that they are fully stopped and none of their processes are still running and that will allow you to do what was suggested in the link.
Do all that again but do not restart the laptop at that point.
Once you have done that follow message 10 in the link. "I killed Edge from Task Manager and when I went into email I had to log back in with email address and password and ticked "Keep me signed in". I then signed out and it asked me to login in again, i.e. it's back to normal".