I sometimes get the same message, and the problem usually resolves itself later and after further attempts.Usually due to an ISP server problem.
You could perhaps try a 'backdoor' method and see if that works. Use the link details provided below, use high security on page opening, and then place the details you use on your regular email collection including password. I have used this website with TalkTalk on many occasions with success, and I suspect it will work with other email providers, as a way of entry to your email?. click here