Did you try using compatability view in IE. It's the small icon in the address bar that looks like a torn page. Click on it and see if they view better.
No compatibility did not work but Firefox did. I don't usually use Firefox as although I like it a couple of sites I have to use for work are set to only recognise IE, and to be even more helpful they don't like IE 10 except in compatibility mode.
You could set up a gmail account and forward all your email to it. This would allow you to access your emails sent to your BTYahoo email from BT and gmail.
Or hope the new mail will be better, I am assuming rashly that BT will have spent some time on testing the email aspects rather than too much time on "enhancing the experience".