The problem and solution: (For anyone who needs this info). Two days ago TB did and update. After the update TB stopped downloading email from all accounts IMAP & POP on multiple email servers (Gmail, Cox, Mailfence, Proton and so on) but I could still send emails. You could see the bottom bar say connecting but nothing would happen. No error message or anything, just no download. I tried all the suggestions listed in the TB 78 FAQ page and only one worked. I use ESET. It also did an update around the same time TB did it turned out. The last suggestion I found to fix this was to turn off SSL/TLS in ESET then restart it. I turned off the SSL/TLS saved it then turned it back on. As soon as I did that it fixed the problem. So the problem was ESET. The root certificate was not properly imported during the installation of the update. I hope this might help others. https://support.mozilla.org/en-US/kb/thunderbird-78-faq#w_after-upgrading-to-thunderbird-78-i-cannot-get-or-send-email-messages https://support.eset.com/en/kb3126-disable-ssl-filtering-in-eset-windows-products