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My Thunderbird (158 Meadow) is very slow sending emails. Up to 30 seconds for an ordinary message. Most often thew people are in my address book but even if they are no the problem is common across all outgoing emails. Windows 11 Laptop 26H2, 64Gb Ram, 500Gb SSD, 200GB free, i7 (12 Edition) Intel I have already checked that my Windows Defender antivirus has the profile folder as an "exception" Compressed my "send" folder Run "repair" on my send folder I have about 500 emails in my send folder I have an IMAP set up with SMTP set to 465 SSL/TLS Normal password I have checked my webmail and that works fine so it is not a problem with hosting etc.

I am unable to access my emails in Thunderbird. Thunderbird opened but does not respond as there appear to be some files /emails that it could not accessed.

I tried deleting the Parent.lock file. I then deleted Thunderbird and re-installed it.

On opening the updated instance, it comes up with the same couple of files/emails in the list. With the same ones seemingly trying to be loaded. See attachment. The files are Invoice 03-10-20 and Ticket_1.pdf

After Firefox & Thunderbird update & Windows (11) update, it takes ages for the email programs to open and the web pages to open. Tried everything, to no avail. Any ideas apart from uninstalling and starting again? The imap lookup takes ages and when opening website pages it takes ages. Googles is very quick to open.

Since Firefox 157, each version is stealing more and more RAM. Why? My Windows XI, on HP with an AMD processor, are constantly losing more and RAM to Firefox. Is there any advice? Or must I suspend all updates?

• • Subject: Severe recurring UI freezes after upgrading Thunderbird from v114 to v150+ — application becomes unresponsive after being left idle**

Hello Thunderbird Support Team,

I'm experiencing a serious and persistent performance issue with Thunderbird that began immediately after upgrading from version 114 to version 150 in September 2026. The problem has continued through multiple subsequent updates and is now severely affecting my daily work.

I've been using Thunderbird for years, and it worked reliably before this major upgrade.

• • The problem**

Thunderbird launches normally and initially works perfectly. However, after I leave it open in the background while working in other applications, it frequently becomes completely unresponsive when I return to it.

Specifically:

- Thunderbird is initially fast and responsive after launching. - After approximately 5–10 minutes, or sometimes after a longer period of inactivity, it begins experiencing severe lag or freezes completely. - When I switch back to Thunderbird, the interface is often unresponsive for several minutes. - I often have to force-close the application through Windows because it becomes practically unusable. - Restarting Thunderbird temporarily restores normal performance, but the problem eventually returns, when it's left idle. - The issue occurs repeatedly throughout the day and makes it very difficult to use Thunderbird reliably.

Importantly, this is not simply slow startup performance. Thunderbird initially works perfectly, and the freezing develops after it has been running for a while, particularly when left in the background.

• • Version and environment**

- Operating system: Windows 11 Pro, 64-bit - Thunderbird version before the upgrade: 114 - Version initially upgraded to: 150 - Subsequently confirmed version: 156.0.1 (64-bit), on September 29, 2026 - Problem first appeared: September 2026 - Problem still present: October 22, 2026 - Current Thunderbird version: 158.0.1

• • Troubleshooting already performed**

1. **Global search indexing:** I noticed that Thunderbird's Activity Manager frequently displayed "Indexing messages." I suspected that indexing might be causing the problem.

2. **Disabled Global Search and Indexer (Gloda):** Unfortunately, this made no meaningful difference. Thunderbird continued freezing even with global indexing disabled.

3. **Multiple Thunderbird updates:** The application has been updated repeatedly since the initial upgrade, but the freezing has persisted.

4. **Restarting Thunderbird:** Temporarily resolves the problem, but only until Thunderbird has been running for some time.

• • Additional unusual behavior: Google OAuth authentication**

On at least two occasions, after force-closing an unresponsive Thunderbird process, Google Chrome unexpectedly opened a Google authorization page saying:

"Mozilla Thunderbird Email wants access to your Google Account."

The page also indicated that Thunderbird already had some access to the Google account.

After clicking "Continue," Chrome redirected to a localhost address (127.0.0.1 equivalent, using a dynamically assigned port), which failed with:

"ERR_CONNECTION_REFUSED — localhost refused to connect."

I suspect this happens because Thunderbird is no longer running to receive the OAuth authorization callback.

I'm not sure whether the Google authorization issue is directly related to the freezes, but the repeated timing is suspicious and could indicate a background synchronization or authentication problem.

• • Impact**

I use Thunderbird extensively for professional correspondence and managing my translation business. These recurring freezes are seriously disrupting my workflow.

The problem has now persisted for over a month, despite updates and troubleshooting. It is becoming increasingly difficult to continue using Thunderbird in this condition.

• • What I would appreciate help investigating**

Could you please advise on how to identify the background process or operation that causes Thunderbird to become unresponsive after it has been running for several minutes?

In particular, I would appreciate guidance on:

- Whether this is a known regression affecting users who upgraded from much older Thunderbird versions. - Whether IMAP synchronization, background authentication, or Google OAuth activity could be responsible. - Whether there are diagnostic logs or performance profiles I can collect while Thunderbird is frozen. - Whether a particular database, profile component, or setting could be responsible without requiring me to rebuild my entire Thunderbird setup. - Whether there are known fixes or workarounds.

I'm happy to provide additional diagnostic information, screenshots, or logs if that would help identify the cause.

I would particularly appreciate a way to capture what Thunderbird is actually doing during these freezes, rather than continuing to try speculative troubleshooting steps.

Thank you in advance for your assistance!

Hi everyone!

I enjoy using Firefox, but I've noticed that browsers can consume a significant amount of memory when multiple tabs are open simultaneously.

I'd like to know if there are any built-in Firefox features or recommended settings that can help reduce memory usage while maintaining good browsing performance.

Are there any specific settings, troubleshooting steps, or features you recommend for managing memory usage without having to close important tabs?

I'd appreciate hearing about your experiences and any practical suggestions. Thanks in advance!

I was referred here from Thunderbird Bugzilla report 2081665.

We are experiencing a recurring problem with Thunderbird 153 on several Windows workstations in a business environment.

The important point is that the problem also occurs with completely new Thunderbird profiles created from scratch. It is not limited to migrated or old profiles.

On one workstation this has already happened to three separate Thunderbird profiles.

Typical sequence:

1. Thunderbird 153 is installed. 2. A completely new profile is created. 3. Mail accounts are configured manually. 4. Everything initially works normally. 5. After some time the profile begins to malfunction. 6. Thunderbird Settings no longer open/respond. 7. The address books still exist, but address autocomplete when composing a new message stops working. 8. Creating another new profile temporarily fixes the problem, but the same behavior can return later.

Troubleshooting already performed:

- Troubleshoot Mode - extensions disabled - tested without the existing prefs.js - rebuilt Thunderbird caches and profile UI state - recreated indexes/databases - completely removed Thunderbird from Program Files, AppData\Roaming and AppData\Local - clean Thunderbird installation - clean profile created from scratch - Thunderbird executable and profile paths added to Kaspersky Endpoint Security trusted applications/exclusions

Removing prefs.js from an already affected profile did not restore the Settings window.

A clean test profile initially works correctly.

We have also encountered this behavior on other workstations. Some users have more than 100 message filters and many folders, so rebuilding profiles repeatedly causes significant administrative work.

Several affected computers had Windows user accounts renamed in the past.

We also experienced a separate issue where the Attach File dialog stopped appearing while drag-and-drop still worked. Bugzilla identified this as the already known Bug 2077590, so I consider that a separate issue.

For comparison, after completely cleaning Thunderbird from an affected workstation and installing Thunderbird 115.3.1 with a clean profile, the same workstation currently works normally.

Because freshly created Thunderbird 153 profiles can later develop the same problem again, simply recreating the profile does not appear to be a permanent solution.

Environment:

- Windows workstations - Thunderbird 153 ESR - Kaspersky Endpoint Security - multiple IMAP accounts - business environment

What diagnostic information should I collect from the next affected profile before replacing it?

I can provide:

- Thunderbird Troubleshooting Information - Error Console output - profile file names/sizes/timestamps - Windows Event Viewer logs - sanitized prefs.js - comparison with a working fresh profile

Bugzilla report: 2081665 Known separate attachment bug: 2077590

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 love Firefox it's my favorite browser that I've used of all the mainline ones I've tried. But I would love to know if there's anything I could do to improve my browsing experience on both iOS and my android. They feel a bit slow while on pc it's quick

What causes Firefox to do a refresh. I stepped away from my PC for 15 minutes and found FIrefox doing a refresh when I returned. Lost all of settings. Putting the icons on tool bar where you want them is one of the frustrating things I have done in a long time and now, I get to make all my settings changes over again plus try to get the tool bar icons where I want them.

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.

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?

Thunderbird (153.4.0esr (64-bit) ) does not display or let the user change its printer setting before launching print preview from the print command. If Thunderbird is set to choose a missing printer, it gets stuck trying to contact the missing device in order to prepare a print preview. It seems to be stuck forever, it does not seem to time out. There is no cancel button. If you close the document tab, you can permanently lose the document if it is a draft email, unless the email service saves it in a trash folder. The printer setting can be cleared if the user manages to learn how to display and clear the troubleshooting information.

Thunderbird needs to display the printer setting and permit the user to change it before launching the print preview operation. It needs to display a cancel button during the print preview operation.

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

Lately, Thunderbird has been using excessive CPU time even when idle. I am on Windows 11 and running the 153.3.1esr release of Thunderbird. It's impacting other applications. When I exit Thunderbird, everything runs faster. Right now it's using over 7% CPU and about 500 MB of ram.

Hardware is HP Pavilion Desktop 590-p0xxx. Intel i5-8400 2.8 GHz 12 GB ram.

Hi,

I'm having a performance issue with Firefox on my computer. After Firefox has been running for a while, it sometimes becomes noticeably slower when I use several browser-based tools and keep multiple tabs open.

For example, I noticed it while using an online one rep max calculator to work out estimated lifting numbers. The calculator itself is fairly simple, but Firefox occasionally starts using more CPU and the browser feels less responsive.

I have several extensions installed, so I'm not sure whether an extension, a particular tab, or Firefox itself is responsible.

I've already tried closing unnecessary tabs, but the problem can still come back.

Is there a good way to determine whether a Firefox extension is causing the high CPU usage? Would checking about:processes or running Firefox in Troubleshoot Mode be the best way to narrow it down?

I'm especially interested in knowing how to identify the specific extension or tab responsible rather than disabling everything permanently.

Thanks.

Hello, so. I just moved from Chrome to Firefox recently. My first move was on my laptop which I enjoyed the experience so I had to try out the mobile version. So far the experience has been pretty okay but I have been coming across occasional crashes and the app is sometimes slow generally. I tried figuring out what's going on by googling how to make the app run faster. I deleted all my mobile extensions but the difference wasn't too visible. I still do experience some last when accessing memory hungry website's like Instagram and Facebook. I know I can just have the apps but I prefer to use the website's (it helps me reduce my doom scroll period). But if I'm being fully honest, I think it's because of my phone in general. My phone is a Samsung A16. The phone on it's own has been generally slow so I think that might be the case but I can't say for sure because the frequency of the app freezes and lack in speed wasn't as common when I was using Chrome. By no way am I saying Chrome is better but I'm just saying that Chrome was faster than Firefox. I'm mostly facing these problems on my phone. Who knows maybe it's my phone still getting used to the app. I really want Firefox to work because it's been a good experience overally plus the added privacy and VPN are a great bonus I never knew I needed till now. Anyways I hope this is just my phone being moody and not the app, I am planning on upgrading the phone soon anyways so I hope that will change. But yeah I just wanted to let you know that this is what I'm experiencing, otherwise everything else has been great. I hope someone can help me out.

Have a great day.

I’m trying to import my email accounts from Thunderbird on Linux into Thunderbird for Android 23.0. On my Google Pixel, tapping “Scan QR code” briefly highlights the button, but nothing else happens. The camera view never opens and no error appears.

Camera permission is granted. Thunderbird is up to date, and force-stopping and restarting the app did not help. Has anyone encountered this or found a workaround?