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I have been using Thunderbird for years with no problems. However recently, Thunderbird very often simply stops responding. Sometimes it just hangs up and sometimes the program bar at the top displays "Mozilla Thunderbird (Not Responding)". If I try to wait for it to respond, it literally hangs for several minutes before it begins to respond again, and often, it simply never starts responding again. It has simply gotten to the point where Thunderbird is practically unusable. All my other application software continues to work with no problems. It's just Thumderbird.

The version number in this submission may not be correct. I can't provide the real version number because of the hangups.

Any suggestions?

System Windows 11 - Firefox 151.0.3 All normal actions from mouse right click have disappeared eg open link in new tab or private window, copy, paste etc etc. The Settings General - Tabs has not changed and previously worked rt click ok. Any help to restore the rt click function will be appreciated.

I have been very happy since installing Firefox as my search engine. Yahoo has hijacked this, and when searching my laptop, it does not seem to exist, but all the searches are headed with a yahoo tab. How do I resolve this problem? Regards Barry

Hello,

My chosen language is English, with French second and US English third. I want to set French as my translation language but when I select 'Translation Settings' I am presented with a menu that only allows Removal of languages. How do I Add a language ? In this case French.

Best wishes

Dear all,

For aprox. 3 weeks now Thunderbird asks me a short time after startup for a login.

It shows up a dialog with the text : "https://caldav.gmx.net verlangt einen Benutzernamen und ein Passwort."

The problem is, that I maintain several GMX - accounts and I've no idea, which credentials I have to enter :/

How can I find out ( without inspecting or debugging the source code ;-) )

THX in advance and best regards!

I am attempting to copy a FF profile from a Windows 11 machine I created it and am using it on to a brand new windows 11 machine on which I have also just installed FF on. Both machines are at FF 150.0.3. I have done a search online for the methods to do this but they have both failed for me.

The first one I tried was simply copying the profile from the existing (source) machine to the profile folder in the new machine however FF never recognized the copied profile on the new machine (I am using profile manager on both machines).

I then tried copying the profile using the method we used to use a while back to copy profiles which is to let profile manager create a new profile in the new machine, open FF so that it creates that new profile in the profiles folder then delete the contents of that profile leaving it as an empty profile (with the name of the newly created FF profile). Then, I selected and copied the *entire contents* of the source profile I was trying to copy and pasted them into the newly created profile I had just zero'ed out on the new machine so that the new profile now had the exact same contents as the source profile. I knew this copy was successful because it took a while to copy all of the data from the source profile to the new profile and the indicator showed it copying.

Again, FF did not recognize the new profile when I opened FF with the name of the new profile in the prof mgr.t.

Could someone tell me what I am doing wrong or what the problem may be? One problem I had when I first copied the source profile to my 32GB USB drive was a message saying "inbox folder is too big for destination system. " The source profile is 12.72 GB so there is plenty of room on the USB drive for it to fit. I have no idea why FF would have an inbox file so I just skipped it. The rest of the profile copied to completion once I did that but its size after copying was now only 7.65 GB, about 5 GB less than the original. Could this be my problem and if so, how do I fix it? Thanks for any help.

Hi all,

I've been using Thunderbird for eons but yesterday morning it started freezing up constantly.

It freezes up ("Thunderbird is not responding") every time new emails are received or any time I take any action while the Inbox folder is open. So, if I delete an email it freezes for a few minutes. If I do anything pretty much, it freezes up for a few minutes. Then it comes back and I can do another action, and it freezes again. This only seems to be happening when I have the Inbox open - if I go to other folders it seems to function normally.

Things I've tried without success: - Troubleshooting mode - Adding exceptions for my profile folders to Windows Defender - Compressing Inbox (and Trash and Junk) - Repairing the Inbox index

This doesn't appear to be a memory issue - right now, memory use for my entire system seems to be hovering at just over 50%. But Thunderbird is still freezing.

My Inbox folder is very large, but it's never been an issue before and nothing significant was added yesterday when it started failing.

Any suggestions appreciated!

Thanks

My inbox folder costently says it has more messages than it displays (I can see the missing ones by searching). I have tried repairing it, looking at filters, etc., but nothing seems to work. See picture. Thank you!

Hello, I can't log in to Facebook, only through Firefox, and that's the problem. Edge and Chrome work fine. I've already deleted cookies and temporary files, and still nothing. This problem has been occurring for a while.

Yesterday I had to change my Spectrum email - I have an old road runner email address and swapped over to spectrum.net server from the old server. In this process I had to update my password to access the server.

When I updated per the instructions from Spectrum I was able to do a normal download into my Thunderbird inbox. This triggered me having to input the new password. I did check the box to update the password and save it. After the one time download I cannot get Thunderbird to download emails. I can send emails with no problems but cannot download. No way can I get a download - it does not on initialization, at the set time nor with the manual request.

Spectrum is no help - their web mail works and it's my problem. I realize this is an old system, legacy and all that - anybody got a magic fix?

Any idea on how I messed this up?

Thanks.

I've been using T-bird since nearly the beginning, and I've always been able to search for a string in a message by hitting the slash ("/") and typing my search string. This appears to be a shortcut for Ctrl+F (on Windows, currently Windows 11).

With T-bird 151.0, when I press "/" it is ignored... the first time I use it. If I press Ctrl+F and do a search, then I can start all subsequent searches in that message with a slash. If I close that message and open another, I must again use Ctrl+F the first time I want to search.

My muscle memory constantly forces me to type "/<string>" to search, but since T-bird ignores the slash, the following characters immediately take action, usually causing me to navigate away from the message, mark them as read/unread or as junk, etc.

Since I can use "/" on subsequent searches, I'm thinking this is a bug, not a feature removal. Can this be checked/confirmed? ...thanks!

I just installed Firefox on my PC haven't had it on this computer since reinstalling windows - I imported my bookmarks and passwords from Edge, thinking it would be a seamless transition, since I used Firefox in the past without much trouble.

Two weeks on, about 95% of every page I open gives an error similar to the one below, and I have to shift+refresh several times to get it to reload before it goes away, (some sites still don't open).

I wonder how common this issue is, and how people fixed it?

Be careful. Something doesn't look right.

Firefox spotted a potentially serious security issue with connect.mozilla.org. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails.

Go back (Recommended)

Hide advanced

Advanced What makes the site look dangerous? The site is set up to allow only secure connections, but there's a problem with the site's certificate. It's possible that a bad actor is trying to impersonate the site. Sites use certificates issued by a certificate authority to prove they're really who they say they are. Firefox doesn't trust this site because its certificate isn't valid for connect.mozilla.org. The certificate is only valid for: *. eero.com. What can you do about it? Probably nothing, since it's likely there's a problem with the site itself. Sites use certificates issued by a certificate authority to prove they're really who they say they are. But if you're on a corporate network, your support team may have more info. If you're using antivirus software, try searching for potential conflicts or known issues. View the site's certificate Learn more about secure connection failures Error Code: SSL_ERROR_BAD_CERT_DOMAIN Jun 5, 2026 10:58:34 AM GMT+10

Proceed to connect.mozilla.org (Risky)

After Windows 11 Home's Microsoft password manager supports passkey, I have troubles with passkeys in Microsoft password manager, not Windows Hello.

1. Firefox failed to login into sites with passkeys in Microsoft password manager tied with sites.
2. After Firefox added a passkey into Microsoft password manager (at that time, no error occurs and display succeed messages), Firefox an Microsoft Edge (Chromium based) fails to login by the passkey. And this trouble continues after Edge replaces the passkey tied with the site.

So, I can't use passkeys in Microsoft password manager.

Have you heard something like this troubles?

OS: Windows 11 Home 25H2 (Japanese locale) Firefox 151.0.3 (x86_64 with Japanese locale. On second trouble, I used the latest version at the old time) Edge: 149.0.4022.52 (Official build with Japanese locale)

I'm not sure exactly when this problem started but it could have been when I had to move my primary email from Xfinity over to Yahoo. Also not sure if this started after a recent Thunderbird update. I can not send new emails nor can I forward old emails. Haven't tried reply but suspect it is the same. This is the message I get: Sending of the message failed. An error occurred while sending mail. The mail server responded: Request failed; Mailbox unavailable. Please verify that your email address is correct in your account settings and try again. All settings and passwords are correct as I can receive and send from all my different accounts using browser. I can send emails from my accounts, on my iphone, though not using Thunderbird on iphone. Account settings and passwords are the same on the phone.

I have been having troubles logging in with my Microsoft email account on Thunderbird (hotmail). When I fill in the name and email address, a pop-up appears with the OAuth2 authentication but the only thing that ever appears in this pop is the message "Unable to connect" with some additional possible explanations.

I have looked online a lot for solution but nothing seems to work. I have cleared the cache, removed all mentions of the email account (it was working before until I added a passkey to the account).

Other reasons I have seen is that the request might be intercepted by certain problems like Apache or Nginx etc. I am running an instance of Nginx on my home server, which is a different device. But I have temporarily turned it completely off but it did not change the situation. The same story with and instance of PiHole, it turns on my homeserver which is a different device and also had to turned off.

The machine I am running Thunderbird on is a Windows machine. I have also tried booting into safe mode with networking but also that did not do anything.

I have tried copying the url on the top of the pop-up window and pasted into several web-browsers. There is does load and I can select the correct passkey to login. But the data that comes back from it is not being given to Thunderbird of course so it does nothing. But the fact that it is able to load outside of Thunderbird makes me think it is a problem on the side of Thunderbird.

Could you perhaps help me set up my email on Thunderbird?