zgroza

Yes, of course I meant disabling SSL to be only a temporary workaround. For me rebooting did not help, nor disabling and reenabling SSL/TLS filtering ... until 1min ago when all of a sudden the problem went away by itself on the host where I had it and where the SSL/TLS filtering was still enabled. Maybe that was another ESET update? I also noticed that at roughly the same time Firefox started to display "bad certificate error" on multiple sites, but it went away after I restarted the browser.

Looks like I'm affected with the same issue. The problem started to appear around 12:00, now I have the same on two computers both running ESET and Thunderbird 78.5.0. Symptoms on my side: In Thunderbird IMAP accounts cannot download new emails, they are stuck with "Checking mail server capabilities" message in the footer. Sending emails is possible via SMTP, but after message is sent, Thunderbird displays popup that outgoing message cannot be saved to "Sent" folder. The workaround for me is to disable SSL/TLS filtering like here: https://support.eset.com/en/kb3126-disable-ssl-filtering-in-eset-windows-products Z.