I have one address at my zoho domain that is constantly giving me an error of "Server imap.zoho.com has disconnected." in Thunderbird. All other accounts work fine. This is consistent across multiple computers. I've had issues with this one account in the past as well. Zoho support has thus far been unresponsive for over a day.

This is the kind of thing that keeps me from upgrading my account.

Any ideas what is causing this?