Wow, thanks guys. This worked for me tonight, as my email again stopped working in Outlook.
Much quicker work around.
The previously-suggested sign-in/sign-out trick didn't appear to work for some people - it didn't work for me - but then I realised from a post by landie57 that he was getting to the BTYahoo Webmail page via mail.yahoo.com rather than via the BT signin1 route. I didn't realise that you could do this, and when I tried it here, it worked. I pointed this out on this forum, guessing that most of us have been accessing BTYahoo via BT and may not have realised that there was another way in. Now many people are finding that it works. No-one has reported that it doesn't work. This is a new discovery and may well lead to a permanent solution soon.
I'm glad you and others are now finding that the exact same trick that I, Landie57 and others have put on the forum works and perhaps BT will listen this time.
As you say either signing in to email via yahoo.co.uk or uk.yahoo.com or mail.yahoo.com works.
For example see my post 7th June 17
I've had issues with downloads on my prime email account via POP3 and I have been able to clear it by login in to Webmail via https://uk.yahoo.com not the BT pages.
The more people like yourself publish this then the better for end users who are stuck with email login issues with their prime email address.
To try and clarify what chamber boy has said.
If you search the forum you will find that the suggestion to log into the Yahoo site has been given many times on this forum over the years when the users were having problems.
The reason that it has been suggested is because there are two email systems running on BT. There is the BTYahoo email and the BTMail system.
BT in their wisdom have one log on page which if working correctly diverts the users to which ever email system they are on.
Unfortunately the log on page on occasions does not always appear to do what it should. The "fix" for this was to tell the users if they were still on the BTYahoo email system to try using the Yahoo email log on page and this invariably worked for them. Obviously this would not work if you were on the BTMail system.
BT are usually aware when this problem exists, if indeed it is even the same problem and cause as your present one, and sort it fairly quickly but for some reason they are taking longer than usual this time.
BTMail email log on
Yahoo email log on