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In the past week or so, I've been having multiple issues with Thunderbird. First, Thunderbird [v140] suddenly started crashing a few minutes after opening.

I checked the help community and KB to try to find a solution and none of the following helped:

Opened Safe Mode, the application continued to crash. Created a New Profile, the application continued to crash. Close Thunderbird, then deleted the Parent Lock File, the application continued to crash. Upgraded to v144.0.1, the application continued to crash.

Uninstall Thunderbird, then reinstalled, the application stopped crashing.

Upon restoring my profile from backup, I discovered several folders were missing. When I checked the Mail folder, I found many of the .msf files were missing but the folder file names were there. So, deleted my profile, created another, and restored from backup again only have the same results. This time I copied the missing .msf files from my backed up profile Mail folder, with the same results. I checked the help community and KB again and found a suggestion to copy the folder files and missing .msf files to the Local Folders folder. After copying the folder files and missing .msf files to the Local Folders folder, the missing folders appeared, including subfolders, but under Local Folders, not in my main account folder. I checked further and saw that all my emails were in fact in those folders, including in the subfolders. So I then closed and reopened the application and clicked to 'get messages' and discovered the message filters weren't working for the previously missing folders that were copied to the Local Folders. I thought OK, I'll just redo those filters.

Later on, I opened Thunderbird to get messages and discovered none of filters for the previously missing folders that were copied to the Local Folders were working. I checked further and found that the folders were there, including the subfolders and emails except... the subfolders under the newest, most recent folder I created before the crashes started.

Here's the kicker... after copying the subfolders' file under the newest, most recent folder and the .msf files back to the Local Folders folder and reopening the application, everything's there again. But after closing and reopening they're, gone again.

After all these years of deleting and creating profiles and restoring from backups with very little or no problems, I've never encountered anything like this.

I need a little help. Thanks.

When I opened the browser, it prompted me about profiles. I clicked on it out of curiosity. However, when I tried to back out of it because I don't need any profiles, it created one anyway. Then whenever I would open the browser, it would prompt me to choose a profile. I don't need any profiles, and it was annoying that there was an extra step. There was the button to turn off the choose profile screen, but I guess I was steadfast in my annoyance, so I deleted the profiles to make it unable to show up. This, however, signed me out of Firefox, and when I logged back in, none of my bookmarks or history were there. I tried the sync option because I at least still had my history on the app, but it did not work. Frankly, I don't care, and I'll just make the bookmarks again. And maybe it should have made sense that deleting the profiles would delete everything with it. But I still think it's insanely stupid to not be able to back out of creating a profile. Took up my time and simultaneously gave me more work to do. I don't want any help or support just needed to voice my feelings.

We're currently on Windows 10 and one of the machines can't update to Win 11 as the hardware is too old. I'm looking at possibly migrating to Linux anyway, as we're already long-time TB and Firefox users. My question is about the migration process and in particular testing/checking the migration is OK, but being able to go back to Windows if needed.

If I start by installing Linux as dual-boot with Windows :

1. Can I leave the TB mailbase on the Windows partition and point the Linux version at the same location (using Settings/Server Settings/Local directory), then use TB on Linux and have the mailbase grow, on the original Windows partition? 2. If so and I need to revert, will the Windows version of TB accept the changes to the mailbase made by Linux? 3. As an issue with Linux is often that you just can't get a program you need in a Linux or browser version, could I e.g. use Linux for most of the time, then boot into Windows to use said Win-only program and at the same time use the Windows' TB until such time as I boot back into Linux? 4. Would the answers to the above differ between IMAP and POP - we generally use POP on PC with IMAP on our phones/fondleslabs, but also have an IMAP account on the PC for if needed. I can imagine that IMAP would facilitate this dual-access better than POP (or would each program have to re-subscribe to IMAP folders when you switch OS), but I'd really like to continue with POP for a fair number of reasons.

Thanks in advance

I'm running Fx Version 144.02 and still do not have a profile selector icon on my menu. I've tried manually to make it happen by going to about:config and changing (browser.profiles.enabled) to true but nothing happens.

This has now happened three times. I implemented the new profiles feature a few days ago, and have three profiles. The issue is that my main profile, every time I reboot my computer/open firefox forgets all my logins. I use a password manager and don't store them in firefox ; this has never been an issue before. It is happening on the same profile each time. My bookmarks/extensions stay the same. This is happening on sites even when I have clicked 'keep me logged in'. There is no site/login that is unaffected - it seems to reset my login status I want to reiterate this is all happening on the same profile - this is not an issue of logins not carrying between different profiles The only other setting I changed is auto-storing passwords on firefox [It had saved my master password accidentally, so.] But there were very few passwords actually stored there, and those sites worked before. I am on Win 11 and have had no issues previously

Hi folks -

I've just seen the update that firefox now allows "profiles" for different purposes (e.g. work, fun, etc.) which seems really handy. But I'm trying to wrap my head around how to approach restructuring my current setup. In particular, do these profiles *all* sync with my mozilla account? Or do I need a separate mozilla account for each profile? (if so, that sort of defeats some of the utlity here unless you're sharing the PC).

I can't tell from the support article, doesn't seem to address this, but you do need to login again if you set up a new profile.

Thanks, Patrick

I have two installations of Thunderbird with each being on a different bootable partition of the same drive so they never get used simultaneously. When I was able to associate both Thunderbird installations to the same profile it was seamless.

My need is to continue having Thunderbird on both partitions but to be able to keep synchronization. I can create two identical profiles set up in IMAP but I assume this will allow for messages already downloaded by the first instance and then subsequently downloaded by the second be flagged as unread. This seems trivial but a moderate inconvenience still. Add to that, I have quite a few accounts in this profile and would find it daunting to have to input completely again all this info. Hoping for a simpler solution.

I also just did the usual copy/paste of the currently used shared profile to the default profile folder for the instance of Thunderbird that alerted me of its inability to use a shared profile but am finding this is not enough to produce an operable profile. Seems it has been flagged as unique to the other partition's Thunderbird (which is on the currently inactive partition).

Any suggestions would be greatly appreciated.

(115.18.0 (64-bit); POP3) Cannot delete folders from app or profile & "About Profiles" shows the wrong profile. This started when I simply attempted to rename a folder in Thunderbird, and emails disappeared *remain in old folder. QUESTION: Can I safely simply set the correct profile as the default (lojbsrwp.default)? ISSUES: -Troubleshooting information shows incorrect profile Roaming/Thunderbird/ (no files since 2017); Settings shows path to correct profile. -Two Profiles showing in /Thunderbird; one appears current. -Profile show folders that do not appear in Thunderbird -Folders w/numbers at the end of file name keep duplicating when I delete, but don't disappear from either -Thunderbird & Profile. Can't delete multiple, duplicated folders. Folders with end-numbers don't match between Thunderbird and Profile. -Troubleshooting information/About profiles/Current: Root Directory & Local Directory show incorrect profile. -Troubleshooting information/About profiles/DefalutOLD: Root Directory & Local Directory shows current profile in use.

I switched to Firefox a few months ago and I've been using the "about:profiles" page to mimic chrome's profile feature. I have 3 profiles, each with their own Mozilla account. How can I migrate these to the new profiles system?

Hi All,

I have recently upgraded to a new PC, reinstalled Thunderbird and imported my profile from my previous machine. However, there are now two profiles using the same email address and I am experiencing that some of my emails go to one profile and not the other or vice versa. This means that if I delete one of the profiles I will lose the emails that are in there but not in the other.

Do you know how I can resolve this?

Kind Regards,

Mike

I have several profiles which were created using About:Profiles. With the arrival of the new official "Profiles" function I had thought this would pick up my existing profiles and make switching between them easier.

It doesn't since the new official "Profiles" function doesn't see my existing profiles. Am I missing something here, or is the new official "Profiles" function somehow different than the previous, manual profiles system?

Hello, i have installed latest TB an try to use it on one PC - This PC is part of company network, users login to windows by domain controller login. there is also a exchange server in the same network. i have created a running and working thunderbird-exchange connection for 2 different users but with the third user its noch working anymore. is there a limit to user accounts on one PC or? Thank you all kind regards andi

Hi, I do not understand the new profile management feature of Firefox and how it relates to sync. I am logged into my Mozilla account that syncs bookmarks, and I use the default profile that I renamed to "personal". When I switch to a newly created "work" profile, I am no longer signed in.

Will the new profiles "personal" and "work" be synced to my account once I log on to both? I am using Firefox on several PCs and I don't want to recreate profiles such as "personal" and "work" on all the PCs manually?

Thanks for a reply.

Oct 23, 2025, 19:35 CST

I FINALLY was able to find the original profile, all messages in the In Box, plus all folders with their contents. 'Lost' when our ISP's ' tech support person ' had me close/remove the TB POP3 account and create an IMAP account).

I need to merge the new small profile (In Box & with basic folders) into - onto the BIG, original, profile. So each time I get/check mail everything goes to, ends up in, the Thunderbird account containing all the OLD data and new working account.

Please remember I am barely TB literate, so start at 1 (A), not 27 (Z)& no tech words. Nor acronyms please.

Thanks! Remain in GOOD health, be WELL, 'n be

• • SAFE!**

Robin

Got up this morning and stared up Thunderbird as I always do but got a 'new account dialog'. All of my emails, folders, settings, etc. are gone. Went through the Help - Trouble shooting process to find the old profile. There are three profiles listed in 'About Profiles' and if I launch with any of them, all I get is a new setup. Freaking out here as I have 10 of thousands of emails, in multiple email accounts, in a relatively complex folder structure which includes online and local folder storage. I have a feeling that Thunderbird updated last night and is the cause of this problem.

Running Windows 10 Pro v 22H2, build 19045.6332 . Thunderbird 140.3.1esr (64-bit)

I have Firefox installed on both my desktop and my laptop. On my laptop, I am able to create and manage profiles; however, on my desktop, there is no option available in the menu (the hamburger menu) to do so.

I have verified that both devices are running the latest version of Firefox, which includes the profile management feature, but I am still unable to access it on my desktop.

Hi, I am about to transfer my profile to a new computer, and have noticed that my profile contains many empty files - about 300 AlternateServices-???.txt, and about 200 folderCache-???.json files.

Can I safely delete these?

Many thanks!

Hello,

I need to purchase a new PC because my old PC was not compliant with Windows 11. I've installed Thunderbird and copied over my data, profiles, etc.

I've noticed that there is folder added to my offline Documents folder called "Thunderbird" and in this is another folder and a file.

Is this normal?

Thank you,

Gordon