My Thunderbird app has been working correctly for months since I installed it. I use Dream Host as my email provider, my email address is jeff@bdmdata.com, and I am running on Win 10. Starting yesterday, it refused to send or receive any of my emails. It provided the following error message: "The certificate for mail.bdmdata.com is not valid for that server..." I also received the following message when I open Thunderbird. "You have received 3 new messages..." But no new email messages show up in my inbox. How can I fix this and get back to work.