There is also the option to get an ISP free email service such as Gmail or Outlook.com (others are available), which may operate better with the Windows 10 email app.
In addition your email address will not change if you move to another ISP.
Thanks. Again, not a great solution when you've had the same email address for 15 years :0(
I know this is probably too late,
Did you try: imap.blueyonder.co.uk/com
Forgot wether your email address was .com or .co.uk whilst writing this but choose the applicable.
This used to work for me on my iPhone after they made the switch to the virginmedia addresses.
Its a long shot and probably months too late but hope it helps.