That would imply the account could have been deleted, possibly because it isn't associated with any account.
Try calling customer services on 0800 800150 and see if it has been deleted and if they can re-instate it. If no joy with CS, post back and we'll see if we can get the mods involved.
Nothing has changed as far as she is concerned except all emails in all folders are gone, this is what makes me think her email is still in btyahoo and not btmail. I can find no options to import an email address within managing emails. All that is there is to create a new address.
The migration from BTYahoo to BTMail is totally under the control of BT and is automatic, no user intervention is required. The login link I supplied is a common link to both systems and logs the user in on the appropriate system.
There is nothing you are able to do within MyBT.
toatally at a loss I think. The only option left is to call bt as suggested earlier, could be a long wait on the phone me thinks.
Unfortunately the only option I'm afraid if the account has been deleted.
You could try changing the password with the forgotten details link on the login page, but I don't hold out much hope. The security question answers will be those of the primary account, i.e yours, if the address hasn't been gifted.
I did finally get this resolved, and thanks for everyone who helped. The problem was that BT moved my email to BT Premier email a couple of years ago when I moved to BT Business for a couple of years, but didn't move me back when I returned to Residential. But the biggest problem was I couldn't change my password as it didn't recognise an answer to the security question of my pets name, I have only ever had one pet so I cant get it wrong. I tried uppercase/lowercase and a mixture, It's only a 3 letter word so cant go wrong!!!!!!. Mix in that lot with the differences between IMAP and POP3, I started from scratch, I got BT transfer from Premier, BT reset my pets name back to the original and then set up a new account on MS Outlook for POP3 and the mail started coming in. What a nightmare!!! Even the chaps I spoke to at BT said they had never come across a problem like this.