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Thunderbird 138/139, Windows 11 Pro 23H2. While composing a message, after a few lines the app freezes. Both the compose window and the main TB window freeze. Only opening the Windows Task manager allows me to close them. This did not happen with earlier versions.

If I save the message every few seconds while composing I can get most of the message back and continue after restarting TB. This behavior is the same in both the normal and troubleshooting TB modes. I can't even find a crash log to send to Mozilla.

Where shall I look next?

Thank you!

This has happened the last two times I've tried to write a reply. I will be writing along and all of a sudden the screen dims and I get the blue circle thingy. Thunderbird locks up and doesn't come back but the red exit button is available. Of course, I lose all the reply I've written. I've never run into this error before and I've been using Thunderbird for years. I'm running v. 139.0.2 (64-bit) on a win-11 laptop, Firefox in the background but no other programs running. I clear my cache at the beginning of every month, so I did that this morning before starting any programs.

Am getting this message along with a recurring download of a specific email (keeps coming back even after deletion) that does not allow any other new messages to be downloaded. I do see new emails on my phone but will not read into Thunderbird??

Error: "Unable to write the email to the mailbox. Make sure the file system allows you write privileges, and you have enough disk space to copy the mailbox."

Tried: Troubleshooting, closing Thunberbird and reopening, rebooting windows system, compacting, etc. to no avail....

Need help with Thunderbird. No matter what I tried always comes back to the same problem.

Problem: Keep getting message non responding. Very buggy, difficult deleting emails (will delete after a prolong period of time > 5 sec). When typing a message there will be no characters then after a short period of time the charterer typed shows up. Sometime without and reason while using Thunderbird it close by itself.

What I have down to solve the problem: 1. Start in safe mode Thunderbird operates as expected with any issues. 2. Win 10 environment, closed all apps and made sure there was no extensions running. Made sure the only app open on the task manger was Thunderbird. NO SOLUTION FOUND 3. Download and install latest version of Thunderbird. NO SOLUTION FOUND 4. Created a new profile file. NO SOLUTION FOUND

Need help, what else is there to try short of a total Nuclear solution?

"The bookmarks and history system will not be functional because one of Firefox's files is in use by another application. Some security software can caused this problem".

How do I resolve this problem?

Hi everyone, I have a pixel 7 that is on the latest release of Android 16

I'm using Thunderbird for Android to access my work server through POP3 secure and it works allowing me to receive and send emails

The widget that I use on my Android to show all my emails including any that come in new mostly shows up completely blank, randomly, after unknown circumstances. When I get a new email I will briefly be able to see the new email subject as well as other emails that are sitting in the box that have already been read. It also will show the current email and previous emails in the non-bold text for a while.

This is really frustrating as I needed to work like a normal app showing things sitting in the inbox that I've already been read at a glance.

Yes, inbox has been selected into UniFi so that way it should be shown.

Unless I misunderstand how to use Thunderbird for Android. I can't see where the problem lies.

I have uploaded a screenshot of the widget that shows unified inbox at the top and the blank area below. This box gets populated as I stated above only when new emails come.

Additional shots show when a new email comes in. It suddenly all appears

The last shot shows that it redraws after reading the new email so that all the red emails are in bold

I have clipped these screen images to protect my privacy on other emails sitting in the display

And helps. Her thoughts would be appreciated, again, I'm assuming this is a bug and I don't know how report this bug adequately

When File Explorer of Windows 11 25H2 tries to access and open an icon-file in the FF (144-64bit) profile's 'shortcutcache' folder, explorer gets Access Denied. The account running Firefox has admin rights.

Looking to the ACL of the profile folder containing the folder 'shortcutcache' show no reason for the blocking. Trying this with a new profile did not help.

Hi. According to my observations, only Mozilla Firefox and Adobe Reader have this problem so far.

Windows 11 + Multi-Monitoring Windows 10 have this Bug not !

Open Firefox, drag the window to the second or third monitor, and suddenly there is another hidden Firefox window on the taskbar of that display. If you move Firefox back to the main monitor, it disappears again. Or you can close Firefox and restart it on the desired monitor.

This is an annoying little bug, and I don't understand why Microsoft or Mozilla haven't fixed it yet. It's easy to reproduce and has obviously been around for a while. Since it only affects the two programs mentioned above so far, an MS update will probably not fix it; instead, the developers at Mozilla and Adobe need to address it.

Here the Same Topic in Adobe Forum. No bug fix to date

https://community.adobe.com/t5/acrobat-discussions/taskbar-phantom-window-when-using-multiple-monitors/td-p/14390169

I hope you release a bug fix soon... but since that hasn't happened yet, I'm afraid it will take a while... I'm surprised, because I'm sure many people are experiencing this annoying problem, and in my opinion it's not a big challenge for your developers.

@Mozilla Please Fix this Bug. I know Windows 11 is not better than Windows 10 but Supports End and many Users and Customers used in Future this OS and if you don't want to lose any more market share, it's important to fix this minor bug for ordinary users too. Thanks ;-)

Performance was already poor in v115, but has gotten much worse since upgrading to 128.5. This is a documented bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1906482 Are there any known workarounds? If not, how can I downgrade with losing all of my settings? I have 7 e-mail accounts and a few calendar accounts set up. This took a lot of time, since several of them require app-specific passwords. Thunderbird complains if I try to open a profile from a newer version in an older version of the software. How can I do this safely?

For some reason text rendered in canvases (used by Minecraft hostings to display console) is distorted. I'm not getting this behavior in other browsers (including Zen – Firefox fork). The issue persists in both stable and nightly versions, with and without hardware acceleration, in safe mode too. Any clues?

Firefox recently sent out its monthly newsletter (Oct '25) with all sorts of options that can be enabled on Firefox. I'm a computer illiterate & foolishly chose some of the options -- don't remember which nor know how to discover them.

Now javascript is no longer enabled on my MacBook Air (macOs Big Sur 11.7.10). I cannot access my protonmail account and many many other sites.

I've gone cross-eyed accessing "fixes" that are labelled "only for advanced users" & am bright enough to not even try.

Is there a simple fix (short of wiping my computer -- with data going back 11 years) that even I can do?

If you have "fixing your firefox for Dummies" then please email me with a solution. [edited email from public community support forum]

I must have done something to mess this up,can someone help me fix this, cannot bookmark. I have used Firfox for many years. Thank you. Joe Daraio email- [edited email from public community support forum]

Hi Can you please help i have tried everything to get rid of this message i have uninstalled and reinstalled i have constantly refreshed and nothing helps,I get the message The bookmarks and history system will not be functional because one of firefoxs files is in use by another application also for quick access place your bookmarks here on the bookmark toolbar. I am not very technical but it is driving me mad please fix this for me Thanks

Hi,

I have 2 machines (Win10 and Win11) with FF 140.3.1esr (32-bit) installed which demonstrates the same failure when I enter one site's url:

PR_CONNECT_RESET_ERROR

Chrome at the same machines goes at this url w/o any failures. Any ideas what to change on "about:config" in FF to allow it opening this url w/o such error?

Hello, Since I updated my iPhones to iOS 26 hell broke loose. On my iPhone 14 ProI can no longer use Firefox as it quits when I open it On my 15 Pro I can use it but most of the time I half only half of the window. I do want you to be my default browser. Can you help, please? How come there is not one article on this? Many thanks! Natalia Great fan of yours

Long-time user here. A month or so ago I switched from 128 esr to 139 release, and since then I have had constant messaging several times a day that folders could nor be compacted. I've verified everything, but the message still happens with annoying regularity. I saw on Reddit that this may be a known bug, but thought I would report it to the forum anyway. Hope that it will be resolved in the next release.