The site could be temporarily unavailable or too busy. Try again in a few moments.
   If you are unable to load any pages, check your computer's network connection.
   If your computer or network is protected by a firewall or proxy, make sure that Thunderbird is permitted to access the Web.

I've been using Thunderbird about a year. Sunday evening (4/5/15), Thunderbird told me it had an update. I said "ok". After that, it wouldn't access AT&T for my emails. My server settings are correct. When I bring up Thunderbird, I see this: Unable to connect The connection was refused when attempting to contact inbound.att.net. The site could be temporarily unavailable or too busy. Try again in a few moments. If you are unable to load any pages, check your computer's network connection. If your computer or network is protected by a firewall or proxy, make sure that Thunderbird is permitted to access the Web. All of those things are fine. The only thing that changed is Thunderbird. Please help.