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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

Latest version of Windows 11 Thunderbird has stopped displaying the message body in the message pane ( right side of the screen) . I have another email client that displays the message body perfectly. It does display the message body of any messages save in a folder but will not display newly received messages in the pane. When I click on the message sometimes I get a white blank screen in the message body display pane. HELP!

Has there been a change to the way that crashhelper.exe behaves in recent releases of Firefox?

If I disable all my browser extensions in the current Firefox v154.0.0 (rel. 18-Aug-2026) and restart my Win 10 ESU laptop then the first time I launch Firefox with a single tab open (i.e, my Firefox Home page with search and 4 rows of shortcuts) I typically see ~ 6 instances of firefox.exe in Task Manager that all disappear as expected when Firefox is closed.

However, if I immediately re-open Firefox I typically see ~ 11 instances of firefox.exe plus an additional process called crashhelper.exe (located in C:\Program Files\Mozilla Firefox) load into memory. On occasion the crashreporter.exe process will also briefly appear in Task Manager and then quickly disappear. All these extra Firefox processes unload from memory as expected when I close Firefox, and if I go to about:crashes or (Help | More Troubleshooting Information | Crash Reports for the Last 3 Days | All Crash Reports) it shows "No crash reports have been submitted" in the past 3 days, so my Firefox browser appears to be working correctly even if crashhelper.exe and crashreporter.exe start running in the background.

NOTE: I can reproduce this behaviour if I prevent Malwarebytes Premium from launching at boot-up (i.e., if Settings | General | Windows Startup | Launch Malwarebytes in the Background When Windows is Started is OFF) and restart my computer, so I don't believe that the appearance of crashhelper.exe (or crashreporter.exe) has anything to do with my Malwarebytes real-time protection.

Dell Inspiron 15 5584 * 64-bit Win 10 Pro v22H2 build 19045.7663 * Firefox v154.0.0 * Microsoft Defender v4.18.26070.9-1.1.26070.7 * Malwarebytes Premium v5.6.5.306-163.0.5714 * Macrium Reflect Free v8.0.7783

Hello Folks, We are a team of 15ppl using thunderbird from last few year and it work flolessly in these years but from last 1week i have been facing a serious issue of : INCOMING EMAILS TAKING A LOT OF TIME TO OPEN AND READ, fresh email when received and after clicking it takes a lot of time of open, having a 100mpbs ILL speed, out of 15 / 12 ppl are facing same issue, even after repairing the inbox the issue remains same, mails are getting downloaded very slowly...we are using google imap server for the same, need help to resolve the same...is it the bug in the latest update 153.0.3 (64-bit) Meadow badge

My Thunderbird app takes some minutes to start up. Updates are OK, troubleshooting does not show any failures. Emailing functions well, no problems. There is a new problem: dragging files to my Explorer has stopped to function.

I have a good HPPro "Desc 400 G5 MT"" PC running on Windows 11 (no problems).

Kindly advice actions to take. Do I loose my Address Book in case I uninstall my Thunderbird and Install a new copy of the Programme. Yours - Jarl Jaatinen, Finland

Goodmorning! Since a couple of days, my TH takes ages to download new messages and when I send a message, it takes at least 20 minutes to show in my Sent folder. I downloaded a new TH but the problem remains the same. I have not changed a thing... What can this be? Its enough to make me change the application... I'm on a Macbook M4.

In the last month or 2, when I delete an email it does not show in the trash folder. I can wait from 5 minutes to even the next time I reboot my puter to finally see it it trash. Sometimes it sends it to the all mail or important folder instead of trash. And if I delete from there, it still takes tons of time to end up in the trash folder...if it even gets there. This seems to be getting worse by the day. I have clicked repair folder, no change, I have cleared Thunderbird's cache, no change. It's also now taking way too much time to load an email that contains a picture. This happens with at least 3 of these gmails. I'm at a loss here and extremely frustrated and about to change these gmails from imap to pop. win10 and TB is up to date. But it doesn't compact folders as much as it used to either. Any help appreciated

I have had Thunderbird from the time I acquired my Mac computer. This week it started to do something new. After a restart I opened Thunderbird. A box came up that says across the top System Integration. The cursor balloons, and hasn't stopped for the time I powered the computer, as least fifteen minutes. You know how the program icons are in a dock across the bottom. With other browsers open, hitting the Thunderbird icon doesn't bring its window into the forefront. This needs either a reset, or possibly a backup first. Is there a quicker way to fix this? Thanks in advance. I am not using a VPN; but I also have Thunderbird on my Windows 11. You might have seen a more recent thread on that installation. I included a screenshot. It was easier here to do that than on the Windows 11. On the Mac, I just had to use Activity Monitor to close out of Thunderbird in order to get its version.

Been using Thunderbird for a number of years but recently the SSD on my laptop became corrupted and I had to buy a new one and install TB and restore my profiles from a backup.

I have two accounts and switch between them with Profile Manager.

The new laptop is an ASUS Vivobook with Win 11 Home and although TB runs ok the first time, if I close the current session and try to open the other account, nothing happens when I click on TB icon on the taskbar. IF I wait for around 5 minutes then it will run

Checked in Task Manager and cant see any instances of TB running, so any thoughts on what's wrong. Does not matter which order I open the accounts.

Why is Thunderbird email for PC and Android suddenly loading and syncing so slow this week...very frustrating. I have a gmail email...gmail site is fine. I've compacted all folder, etc and IMAP server server setting for years.

Hello Folks,

We are a team of around 15 users who have been using Mozilla Thunderbird with Google IMAP for the last few years. Until recently, Thunderbird has been working reliably without any major issues.

However, for approximately the last one week, we have been facing a serious performance issue with incoming emails. Around 12 out of 15 users are experiencing the same problem.

The main issues we are facing are:

Newly received emails take a very long time to download. After clicking on a newly received email, it takes a considerable amount of time to open and display the content. Emails appear to be downloading extremely slowly, even though our internet connection is a 100 Mbps ILL (Internet Leased Line). The issue is affecting multiple users simultaneously, so it does not appear to be limited to a particular user's Thunderbird profile or PC. We have already tried Repair Folder / Repair Inbox, but the issue persists. We are using Google's IMAP servers for our email accounts.

We are currently using Mozilla Thunderbird 153.0.3 (64-bit) – Meadow Badge.

Could this be a known issue or bug in the latest Thunderbird 153.0.3 update, particularly with Google IMAP?

We would appreciate any guidance from the Thunderbird community/support team on how to troubleshoot and resolve this issue. If there are any recommended settings, logs, diagnostics, or Thunderbird configuration changes that we should check, please let us know.

Since this issue is affecting 12 out of 15 users, it is becoming a significant operational problem for our team.

Any help or suggestions would be highly appreciated.

Thank you.

I've done EVERYTHING.

New install of latest version. edited profile to point to saved data on USB external drive DELETED every instance of lock files terminated task numerous times. rebooted 3 times...

What now???

Thunderbird running 70-80% CPU with status bar showing. Once status bar is removed this drops. Have noticed some bug reports mentioned Linux but I'm on Windows 10 ESU (up to date). Updated TB to 153.0.3esr but no improvement. Tried troubleshoot mode but no improvement. Also noticed that emails aren't getting moved to the deleted folder from inbox. Checked today and none had been moved for 3 days. I deleted some of the older ones from 'Deleted' and then it did update.

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.

When I write and send a message. A window comes up saying copying message to sent folder and then it won't close. i.e. it just stays there. When I open up thunderbird again it says the message has been sent but I still can't close the window that says copying message to sent folder.

Wäre es nicht Sinn voller mal Firefox so zu Optimieren das er nicht gleich 50% des Arbeitsspeicher belegt. Ich beobachte schon länger das wenn Firefox eine weile Läuft sehr viel Ram braucht. Da gibts andere Browser wie Brave die viel weniger Ram belegen als Firefox.

Könnt ihr da nicht mal ansetzten und was Optimieren Bei den Ram Preisen Aktuell kauft man sich ja kein neuen RAM.

mfg solo275

For a few days I'm having trouble with Asana mails (notification mails informing me about replies, comments, etc).

Clicking on the mail to view it freezes Thunderbird for a good 5 seconds while one CPU core spins at 100%. This only happens with Asana mails (or at least I haven't found any other problematic senders).

I guess it's a problem with validation or parsing of the mail's HTML content. But I don't know how to debug this.

I can't pinpoint exactly when it started happening, but it was around the time I've switched to the [new snap release track](https://support.mozilla.org/en-US/kb/channel-choices-thunderbird-snap-and-flatpak#w_snap-channel-changes-in-2026). But since this happens with Snap and Flatpak I think the culprit may be the 153.0 update.

Things I've tried:

• Clearing cache and msf files.
• Troubleshooting mode with add-ons disabled.
• Reinstallation. Creating new profile + importing old data.
• Switching from Snap to Flatpak
• Switching Message Body display to Plan Text or Simple HTML.
• Disabling HW acceleration.
• Checking console for suspicious output.

Anything I can do to create handle the problem or collect information for a proper bug report?