Can no longer access blueyonder emails on iphone.I get the following error message: The mail server 'imap4.blueyonder.co.uk is not responding', how do I fix pls?

Hi there

As I've mentioned above, I can't seem to access my emails from my blueyonder account on my iphone. When I first set up my account on the phone, I had no problems at all receiving emails. Then recently, just out of the blue I get the following error message: 'Cannot Get Mail, The Mail Server 'imap4.blueyonder.co.uk' is not responding. Verfiy that you have entered the correct account info in mail settings. I definitely have the right settings, I even checked with Virgin but they are not able to assist with my problem. Has anyone else experienced this problem, if so,how did you fix it? If you could explain in simple terms as I'm not tech savvy!

Many thanks!