Thunderbird Community Forum

I am having constant problems for months now with Thunderbird freezing and message not responding. It appears to happen mostly when trying to empty deleted folder in block like 20 or more. If I deleted in blocks of four all is ok. As soon as I try to delete a larger amount at once it freezes and displays the message Thunderbird Not Responding. I have followed u tube videos to the letter to attempt repair with no success any ideas please?

Hello, I am having an issue that Emails which are displayed in the reading area disapper for appr. 2 minutes. Afterwards they appear again. I have not been able to find out if this is a problem in Thunderbird, or if another application is causing this. I have read an article that Avast Antivirus is temporarily locking folders during scan. Maybe someone has had the same topic and can give me a hint where to search for the root cause. Thank you.

My Thunderbird connected to my gmail is running slow. Thunderbird is not running slow on my other (non-gmail) account. It takes 10-15 seconds for an e-mail (from gmail) to be deleted or moved within Thunderbird. I have tried "compacting folders" and "repairing folders" and that does not help. Please help!

This seems to have occurred in the last month or so.

Whenever I click on a message in the folders pane, the message is not displayed correctly in any of the three layout views but, if I am offered to display in a browser, it does! Also, if I select 'Edit as a new message' it displays correctly, as also do iPhone and iPads. The screenshot shows the problem?

Any ideas, anyone?

I upgraded my system to Kubuntu 26.04 LTS and started Thunderbird. The window where messages are listed was covered with Thundrbird presentation asking for donation. Only edge of one message is seen above the presentation and I cannot get to the list

I'm on a 15" MacBook Air M5 running and updated OS to Golden Gate 27.0 a couple of days ago. when I Open Thunderbird the emails are up but page is blank, just spinning pizza wheel. I've force quit Thunderbird and restarted and force quit and shut down several times but ends up with the same result... just the spinning wheel. Any suggestions ?

I'm running Thunderbird 156.0 on Windows 11 with ten IMAP accounts (Gmail, Outlook.com and Zoho) plus one Exchange account served by the Owl add-on, and until recently about 30 GB of mail held locally. On starting Thunderbird, folders are destroyed and re-created empty. It happens often, but not every time. The summary files are deleted, and in some cases the whole folder directory goes with its mbox message store inside it. The folders then come back in the folder pane holding nothing, and Thunderbird downloads all the mail again over several hours, re-indexing as it goes. When a folder directory has been re-created, it appears on disk with a numeric suffix, so one of my folders now lives at COMPLIANCE-1.sbd with an abandoned COMPLIANCE-2.sbd sitting beside it. Column layouts and favourite-folder flags are lost at the same time, because they live in the summary files. It happens on ordinary restarts, rather than after Windows updates or sleep.

Those orphaned directories have let me date three separate occurrences: 18 August 2025, 19 February 2026 and 19 September 2026 — those being the occasions that happened to leave orphaned directories behind. Most leave no trace, because the folder refills and the evidence is overwritten. Each has the same signature. A folder directory is created, and roughly five minutes later a summary file of about 1,200 to 1,500 bytes, which is an empty summary, is written into it. In the two older cases it was never touched again. In one event eleven summary files across two folder trees were written with an identical timestamp to the second, so it appears to be a single operation across a set of folders rather than something that walks through them one at a time. One of the destroyed folders left its mbox stores behind, orphaned with no summary file, while another was deleted whole with 50 MB of mail inside it, so there seem to be two different outcomes in the same event. Bitdefender is running, but its quarantine holds nothing from the September event, and there are no Thunderbird entries in the Windows event log for that period.

The part that may be useful is that I have reproduced it. On 19 September I renamed folderCache.json aside with Thunderbird closed and restarted. Eight minutes later folders were destroyed. The twelve I could identify were all children of INBOX, across two different mail providers, though other folders elsewhere were emptied in the same minute. The Exchange account served by the Owl add-on was untouched. At the moment of destruction the Activity Manager showed "[NONEXISTENT] Invalid folder: INBOX^Practice Filing (Failure)" on the Gmail account, where the correct hierarchy delimiter is a forward slash rather than a caret. My folderCache.json is 5.2 MB with about 13,000 entries, of which roughly 1,200 point at summary files that no longer exist and 9,600 sit under an obsolete lowercase profile path from the 129 to 139 version window. I would rather not delete it again given what happened, so I'm looking for any idea of what triggers this on an ordinary restart, and whether there is anything I can set that would stop Thunderbird discarding local folders when it decides they are missing.

I am going in circles with this. If I build a new profile, is there any point bringing the old configuration across, or would that just reimport whatever is wrong? I assume the address books and filter files are safe and that folderCache.json, prefs.js and the unified-folders directories are not, but I do not know whether the problem lives in the profile at all, or in how Thunderbird handles an account set this size.

Any ideas?

Since the latest update, the uploading of new emails from the server can take minutes to hours. I know the emails are on the server, because I can see them by logging onto my email client on my iPad. Why has Thunderbird suddenly become very frustrating to use? An example which just happened - I was required to enter a 6 digit code to be able to confirm my account before I could submit this question. I waited, and waited and waited to see this code in my Inbox. Finally I went to my iPad to get the code, so I could submit this question. It was there as I expected, but not in my Thunderbird Inbox for another 10 minutes. This is happening far too often, so I am contemplating finding another email program which is not so frustrating.

I am running Thunderbird 140.9.1esr on openSUSE Tumbleweed.

For a long time now, Thunderbird often runs at high CPU (80-100% of one core), for several minutes at a time (5-10 minutes). This seems to happen many times every day, with no apparent cause from my end. (I just got back from Lunch, and the fan on my laptop was going crazy because of the high CPU.)

What can we do to identify and fix this issue?

We are facing issues with Thunderbird mail application.

Incoming emails are not being received in Thunderbird. Thunderbird is running very slowly and frequently becomes unresponsive. Sending and receiving emails is taking a long time. We have already restarted the application and system, but the issue still persists.

Kindly check the mail server settings and Thunderbird configuration from your end and advise on the necessary action to resolve this issue as soon as possible.

Your prompt support will be highly appreciated.

I don't know where to start. Ever since the update to version 154 I've been having one problem after another: switch from Comcast to Yahoo causes problems with THunderbird, slow indexing, arbitrary folders showing up in different email addresses (confuses my account with my wife's' some of that may be problems dealing with gmail issues), lost email folders after attempted repairs. Three months ago there were none of these problems. I have not yet tried switching back to the last updated version of 153, but 154 does seem to have many more problems. I've run troubleshooting.

I am not a computer expert and there is only so much time I can devote to this, but even computer repair services I've called are at a loss and very pessimistic about the ability to repair things. In all the years (over a decade) my wife and I have used Thunderbird, there have never been as many problems as have surfaced in the last two months. Maybe the best that can be done is to hope that updated versions will gradually fix these issues. I will say that my Macbook Air (M2 chip) has far more problems than my iMac (M1 chip). I have checked and rechecked all server settings (smtp and imap). Although more cumbersome, things perhaps work better if I just stick to webmail options.

All of a sudden I have to open the program twice for it to run. First time the screen opens but it is just blank and says it is not responding. So I close it and then open it again and it is fine. Anyone know why this is happening?

Hi,

I'm running the latest version of Thunderbird 140.12.1esr on 15.7.7 (24G720) on an M1 processor.

I'm witnessing Memory leak > Thunderbird who usually use 800MB jumps to Gb up to 60Gb

It makes this version unusable.

Here is a loom of the incident: https://www.loom.com/share/0b8e661b42d64d749d80adfd71fd1e04

+ a screenshot

Anyone can help ?

Best Olivier

If Thunderbird startup is stopped before tabs are loaded, they are lost. The tab fields at the top of the screen remain but they are empty. Evidently, tabs are stored only in a temporary location. This is a very annoying bug. Is there a way to recover them?

I download my e-mail from Yahoo using POP3 and OAuth authentication. Downloading works fine until I reach a particular e-mail. Thunderbird says "Downloading message 27 of 52" (or whatever) and then it will stall and eventually timeout. When I go into Yahoo webmail and archive the next message out of the inbox, the rest of the e-mails download.

I know exactly which e-mails can't be downloaded. They are from my Moen Flo account (a device that monitors water use at my house). It is not spam, and it is vital that I receive these e-mails. So identifying the problem e-mails and deleting them via Webmail will allow Thunderbird to download the rest of my e-mail, but it doesn't solve the problem. I saw someone else on the forum had the same problem with USPS tracking e-mails. There are probably more legit e-mails that cause Thunderbird to choke.

Having to go in to webmail every day and delete every legit e-mail that causes the downloading to fail is not a solution. If the e-mail client doesn't work unless you go into webmail first, then what's the point?

Not an ISP problem - I can download with another e-mail client through the same network.

Not an antivirus/firewall problem - I tried it even after uninstalling antivirus and turning off Windows Defender.

This is definitely a Thunderbird problem. I am 30-year IT professional and I have tried everything to narrow it down to this.

So how can we get the developers to look at whatever combination of characters is causing Thunderbird to choke when attempting to download e-mail? I have sample e-mails that reliably cause the problem.

Thank you.

When I went to open Thunderbird this morning it told me the programme was already running. It certainly was. There were an infinite number of Thunderbirds running! After failing to close them all, I closed down the computer and started it again. Thunderbird was veryslow to load and when it did, the display for my inbox was of emails from four years ago. I strted to scroll down using the mouse but then I noticed it was scrolling by itself. Eventually it reached today and had downloaded some messages.

The system is though running very slowly, it takes a while for a message to open and messages which I have left open at the top of the screen for action are not showing subject or content. I operate a complicated system of filing in subfolders of messages I need to keep for reference and the subfolders seem to be ok.

I started using Thunderbird many years ago when a IT friend recommended it because, unlike Outlook, Thunderbird has an infinite capacity. I am wondering however if I have taken that too literally? I must have thousands of emails in my IN box going back years, plus a structure of some subfolders which are never used. Is that likely to be why I am having problems and would I be well advised to do a bit of a mega clear out? Advice please from the more tehnically skilled would be much appreciated! Carol

I see others are having this same issue with no resolution in sight.

The company I work at is unable to print anything through the print preview in Thunderbird. The current work around is to download, open, then print the file.

Does anyone have any further information on this subject besides going through separate avenues to fix the problem?

Thanks!

Hi, I've been back to Thunderbird since May, and while I'm happy to be moving away from gmail.com I find the experience with thunderbird a little disjointed and frustrating.

And it would be fine if it was not also sluggish.

I have approx 100'000 emails in All mail, 15'000 mail in inbox,203 mail folders and 160 email rules each with about 3 sub-rules each.

When I get a 2 Factor message sometimes it only take 10 seconds, sometimes it takes minutes, sometimes it never appears until I press the "check mail" button, it's never clear what "check mail" even is doing, if anything at all.

My computer is a 16 core Ryzen 5950x with 64gb ddr4 and it is otherwise very fast and I don't have any crapware installed like "mcaffee anti virus" or whatever.

I can't tell but it feels like it is applying every rule to every email in "All Mail" every single time and I'm pretty sure that is why it is so slow.

However the interface is very obtuse about what it is doing, so I have a hard time finding what the problem is.

Now, I am not going to delete my messages and I am not going to have fewer rules. but I think the rules should only be applies to newly received messages and that should only take milliseconds. Also, it should be easy to tell, what it is doing and how much time that takes ?

This indicator, is mostly meaningless

And this window, really doesn't say that much about what it is scanning

If it were saying how many email and which folders it applied rules to

It would feel a lot less sluggish if I was able to see what it is doing and be to tell if it is doing something or just hanging, it is very frustrating to wait and not even be sure if anything is happening at all !

And I greatly suspect that my problem is that it is applying All rules to All mail, not just the new mail, and if that was fixed and the activity manager made more descriptive and responsive, it would not feel so slow and frustrating and I would know what to change to make it faster !

But right now, if I didn't have such distaste for google, I would just go back to gmail which never made me wait more than 2 seconds for anything.