cannot verify exchange account macbook

I have had an exchange account I use with apple mail on my macbook for years. Suddenly it has stopped working. When I enter my password I receive the message "Cannot verify account." Occasionally it will accept the password and be ok for a few days, then it throws me out again. I would try to delete the exchange account and reinstall it, but it will only allow me to delete it on all of my ichain-connected devices, which I would prefer not to do. Otherwise I can only disable it; when I seek to enable it again I have the same problem. Any fixes?