Ok - with my ongoing Britbox thread I've now discovered another issue.
Logging into MyBT with my details it skips the MyBT product page and goes straight to email page. It does display email but I noticed in the top right corner my email address changed to end in @btinternet.com.
From within if I now select MyBT it opens up another login page and gets stuck in a loop.
Solved! Go to Solution.
Thanks for the info although no idea why this has just started to happen.
However, as you note, they might be interchangeable for email but not for MyBT login.
Currently been on to BT helpdesk for 50mins and frankly its the worst "on hold" music I've ever heard and becoming a bit of a joke.
...well, no more music, it cut off!! Grrrrrrrrrrrrrrrrrrr
As @licquorice as far as email sending or receiving email the the addresses are one and the same but they are not one and the same when used to register/sign in to a website