You're lucky. The last person who criticized Thunderbird saw his PC melt and was reborn as a DIsplayWrite machine. We don't let the hit squad out often anymore. Sounds like you got hit.

On a slightly more serious note, are you running an antivirus program? those errors sound to be too frequent than mere chance.

I run AVG on several systems, and have no intention of crippling it; it keeps catching malware in my incoming emails. When Mozilla can't get along with AV programs, I don't blame the AV programs. Thunderbird's box, claiming invalid certificate errors, clearly offers to "permanently" record the security exception, then fails repeatedly to do so, at a rate of over 100 times since Jan 1st over 4 or 5 e-mail accounts, about every second or third day. I regard that as extortion meant to drive me from using certain software, clearly demonstrated by Mozilla Contributors railing and ranting against Network Solutions and AV programs. I just fixed it by setting up my accounts in Apple Mail on another computer. Apple Mail managed to download over 1000 emails without once denigrating their certificates and demanding that I spend time doing something about it. At the age of 77, after having been maimed and disabled by a drinking driver in 1985, and having a benign but extremely painful tumor cut out of my spinal cord last year, I need that time to lay down now and then and wait for the pain to stop. I'm fed up with the grinding hassle of using Thunderbird in Windows 10, don't have that time to spend on adolescent and spiteful programming gamesmanship. Anyone who thinks that a constant barrage of unnecessary and unwanted error messages will force me to join and endorse their political software cult can go teach their grandmothers how to suck eggs. I will keep a copy of Thunderbird to use offline, so I can read my old emails. Otherwise, I'm voting with my feet, and advise anyone who wants to use a hassle-free email client to do the same.

AVG is a known problem child where email is concerned. As you have no intention of crippling it, you will have to put up with the crippling it does to your system.

Or you could attack the problem by trying some sensible diagnostics. See https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems Yes the title says memory, but the steps are largely the same for everything.

I further suggest you either cease and desist on the ludicrous conspiracy theories or put up with being removed from this community. If you want support, someone is sure to help. If you insist that your antivirus, the probable cause, is inviolate. I will not be one of them.

Click the view button and see what site your certificate is for! Clearly the message is the name given is not the name on the certificate. Given AVG is known for using dodgy self signed encryption certificates, it could be for it. Interestingly Thunderbird forces the user to make the decision as to the trust they have in these self signed certificates. Windows just lets any program insert an certificate into it's store.

It could also be because you are using SSL/TLS on a server without a correct certificate as this test shows. You have an opportunity to add an exception if you are sure it is right. Clearly you have not done that at the time you took the screen capture.

I could not test your first site as you cropped off the end of the name and port, but seriously what I can see does not look right for a mail server name.

Do you not read English? As previously stated, I have clicked on the option to make the alleged security exception permanent every damn time - scores of times. Mozilla Thunderbird refuses to honor that request; by the 2nd or 3rd day, it raises yet another batch of error messages. This has been going on for months. Instead of addressing that functional failure of Thunderbird to process the exception permanently, members of your group have ranted about how NS certificates are "cheap", how my AV program must be the problem, and how I have failed to provide you with enough private information about infrastructure in which I have no skill. Furthermore, after getting jacked around with error message boxes that don't function as advertised, and jeered at to boot, I have no reason to trust any of you with any of my private information. I have switched to Apple Mail and am having no such problems with either certificates, or my AVG AV software, which I use on both Windows and MacOS machines. That kind of bull-headed arrogance ruins your own reputation. I resent having to deal with it - Windows alone is pain enough. I'm fed up with trying to tell you what doesn't work in your software. You don't listen.

Come on, be honest. You're having fun with all your ranting. If you're really confirmed that we're all heathens, you would quit your responses, but you like playing the injured party. Just let it go. You say you resent dealing with it, but then you continue on and on and on. Just go.

So you missed the part where I switched to Apple Mail GIGO

Besides that, no one in my age group has to answer anymore to high school mean girls. And I've been working with and programming computers since about 1962 and know buggy programming when I see it. The lack of logical consistency gives it away.

Besides that, no one in my age group has to answer anymore to high school mean girls. And I've been working with and programming computers since about 1962 and know buggy programming when I see it. The lack of logical consistency gives it away.

Dispalywrite - good one David!

And Mean Girls - another good reference.

All in good fun. But hey, no one here has the time or interest to mess with anyone's computer. And as someone who has been programming since 1975 (you beat me by 10), a bug is a bug, IF it is a bug, no matter what your age.

And, this is still a duplicate of https://support.mozilla.org/en-US/questions/1400967, so locking. I'm checking with a developer and will reply there in due course.