Since November 2020, I suddenly cannot receive message from a few of my accounts. Thunderbird show now error and log. On Account1, when I click "Get Messages", it asks for security exception, I accept, then status bar says "Connected to imap.<hostname>" (<hostname> replaced). The app does nothing from there, shows the status message indefinitely. On Account2, when I click "Get Messages" then status bar says "Connected to imap.<hostaname2>" for indefinitely. The both accounts are hosted with the same provider and server. I have other accounts with the provider that work. Server settings for all the accounts are SSL/TLS port 993. Server is accessed using hostname containing domain name in my possession. The provider uses Let's Encrypt certificates in name of their domain, hence the security exception asked and me accepting it. This setup has worked for 10+ years with Thunderbird. You did a sudden change and flawed receipt of my business emails! The FAQ for Thunderbird 78 doesn't work. I have reduced the security.tls.version.min to 1 and didn't solve the situation.