Thunderbird Community Forum

OS: GNU/Linux Thunderbird Desktop

Is it possible to set up a TLS client certificate for authentication with SMTP, as it is with IMAP?

It works fine on the K-9 Android client for both IMAP and SMTP.

Is there a reason why this hasn't yet been added as an authentication method for SMTP?

Thank you!

Best Regards

I keep my mail (both sent and received) in local mail folders. My server is gmail, and sent mail is put in gmail's sent folder by default. Every few months, I copy those messages to a local folder, and after I back them up, I delete the server copy.

What to my dismay, I discovered today that only the message headers, and not the messages were present in the local folder, though they had been when downloaded. Looking at the file sizes, I found the sent file to be 0 Kb, and sent.msf 255 Kb, when sent should have been around 60 Kb long.

I have been able to restore the messages from backup (whew!), but I have no idea how then sent file was wiped out. I know I did not do it.

Has anyone else had this happen? Is there a preventive measure I should take?

Hello,

I am on Thunderbird 150.0.2 for Windows.

I am really suffering here. I need to change the font weight of unread messages. In a non-threaded list.

The default weight I get with my preferred font (Trebuchet MS) is not bold. It is BLACK. When I say BLACK, I mean ultra bold, display font, heading weight. Heavier than the boldest font that even exists in the font family. Thunderbird is creating this ultra mega black font by taking the bold font variant and applying a faux bold effect to it. The result is that the text is so heavy that it takes up twice as much horizontal space as the ordinary bold font variant. This becomes a usability issue because it's not possible to see the date, sender, and subject at the same time.

I have struggled and strived with userchrome.css. Spent hours combing through forums here and elsewhere. I've already enabled the mystery setting in the config editor. I put userchrome.css where it is supposed to be.

I saw a blog post from Mozilla that says "userchrome.css is not supported". What is the actual meaning of this? That it has been actively blocked from working anymore, ever, for anyone? Or that users are taking risks if they create userchrome.css? Why can't developers speak plain language? "Not supported" could mean many things.

When I go to the Style Editor, userchrome.css does not exist there. Which leads me to believe that user customizations are absolutely deprecated and we are not permitted to use userchrome.css.

I tried editing some of the rules in the Style Editor, but could not determine any way of actually storing the changes. When I click Save, I get a dialog where I can **EXPORT** the file. But I can't seem to actually save the changes, because CSS files do not appear to exist in the installation directory. It must be compiled into some library.

This is extremely unsatisfying and super frustrating. Just getting straight answers to things is super difficult, nothing stays the same for more than a couple months, and up to date information either does not exist or is not found by any search engine.

So, please help. I just need to change one setting, the font weight of unread messages. Since Thunderbird is allegedly open source, I thought I would have some ability to make such changes. But the Style Editor doesn't seem to actually be an editor, but merely a read-only interface to precompiled rules? If I wanted to change the font weight of unread messages, would I be forced to compile my own version of Thunderbird? I'm not competent to do that, and it would probably either prevent updates, or the updates would break my changes.

Please help, I am super desperate. I need to see the date, sender, and subject all at the same time. That doesn't seem like an unreasonable ask.

I would gladly pay for an email client that gives me control over my data *and* allows me to control the UI, but apparently that doesn't exist.

Når jeg sletter mails, bliver der stadig ved med at vise en mails som ikke er læst med et flag på bundlinien . Først når jeg trykker på eks. kladeer og derefter indbakke forsvinder dette.

Hi,

My mail account was recently migrated to office365, and I saw that Thunderbird v145 and later supports this natively without the use of a plugin.

However when I follow the instructions to set this up I don't see the Account hub in the same way that's shown in the article.

https://blog.thunderbird.net/2025/11/thunderbird-adds-native-microsoft-exchange-email-support/

instead I see the one attached.

I've tried this on both Linux (ubuntu 24.04) and Window 11 both with my original profile and a completely blank installation. On Linux I've used both the Canonical supplied Snap (from the monthly/stable channel) and the download directly from thunderbird.net.

Any help appreciated.

Many of my emails received are auto marked/shown as having been read. This means I never know which of my many emails received are new and which I have already read. Particularly annoying as I have a number of aliases and a number of folders to put them in. I am actively considering going back to MS Outlook, which would be regressive.

Whenever I create a new folder in one of my accounts, the new folder appears listed under my Unified Inbox instead of being listed under the account. It is super annoying, and then to correct it, I need to open Unified Inbox properties and uncheck it from the folder list. I only want Inboxes to appear in my Unified Inbox. How do I stop this from happening? Thanks

Email will not send. Message-- "Sending of the message failed. An error occurred while sending mail. The mail server responded: Email rejected. Please verify that your email address is correct in your account settings and try again." I am not sending to another person but testing with my personal email. Thank you.

Does Thunderbird use an internal PDF print driver? I can't print PDF attachments in color from an email. I've checked my print settings but Thunderbird only prints black. If I save the PDF file and then double click it, Adobe comes up and prints it full color. I'd appreciate it if it can brought to soneones attention.

Thank you.

I have new e-mails from some company. I can search for the company and the e-mails show up (as recently as today) but in the list I only see e-mails as recent as 35 days ago. I see TB periodically download new messages but they don't show in the list. I have searched all over for a solution and nothing has worked. I have no Message Filters and I have no Quick Filters active. I have tried both repairing and compacting the Inbox. Does anyone have anything else I can try?

How do I change Thunderbird's icon back to the older version? The new version looks a lot like Signal's icon. When I have a taskbar full of icons, I have to look carefully to make sure I'm selecting the correct icon for the app I want to switch to. It's annoying. Thanks

Sorry for long post. Struggling to get backup done, running out of time and other things in life now getting really urgent . Got my Yahoo Mail headache again today. Please can someone advise me? Thunderbird 150.0.2, Mac OS 10.15 7 Catalina, 2018 Macbook Pro.

Not tech-savvy so finding it hard to find what settings to use in TB. Other people's post answers always seem to show dialog options I'm not seeing on my computer

AIMS: - Prevent folders from deleting in my backup, if I delete stuff on Yahoo. - Backup Yahoo emails to a stable, local copy on an external drive, so I can access old emails + attachments independently without it trying to reconnect / synch with Yahoo Mail - After backup, delete more mail to reduce YM storage from 39GB to less than 15. Feel reluctant to do this yet, as I already lost a big folder of work from my backup by trying to muddle my way through this. - Ideally would like to end up with a local copy I can access in Mail Backup X What I've tried; - Backup using Mail Backup X. Took 18 hours and some large folders were incomplete so I tried again after splitting them up in Yahoo Mail. I liked the software but something went wrong on the 2nd try and it now won't connect to Yahoo at all. Deleted and replaced 3rd party password multiple times. Server details are accepted, but then the icon just spins endlessly, hence trying Tbird instead. Deleted the MBX account which meant no error logs available (Yes. I should not have done that). - Tried both IMAP and POP backup using TBird - have added TBird ImportExport add-on but have no idea what settings to use, advice welcomed Questions/assumptions that may be wrong: - Was advised to use server export.imap.mail.yahoo.com, what's the reason for this and would it work? Can't remember if Yahoo allowed me to enter this setting. Sorry, hard to recall as I tried so many times. - POP only backs up 1 folder - Inbox. Really?? that's not a solution then - TBird's default is IMAP so surely it would always try and connect to synch, and so would any copied backup accounts? - if I get the ImportExport add-on settings right, can I *really* achieve the goal of a local offline backup I can trust, that I could keep on an external drive and access later via Mail Backup X?

I tried everything and I mean everything and I am still getting this error shown in the image attached. Can someone help?

• I removed saved passwords
• Un installed and re-installed thunderbird
• created new profile

P.s. This is an office 365 account

Hello,

I recently upgraded to a new PC from Windows 10 to Windows 11. For some reason I can not open links in any emails, even if right clicking them. I have gone through all steps here: http://kb.mozillazine.org/Standard_diagnostic_-_Thunderbird but nothing has changed. I have disabled Win Defender completely and still no change.

Any idea what I am missing? I am at a loss at this point.

Thanks for any advice or direction.

SIMPLIFY THUNDERBIRD IT IS EXCESSIVLY COMPLEX. I CANNOT EVEN SEE HOW TO MOVE MESSAGES FROM THE INBOX TO THE RELEVANT FOLDER IN MY LIST. I PERSONALLY BELIEVE FIREFOX AND THUNDERBIRD ARE OVERCOMPLEX AND NEED SIMPLIFIED. SIMPLES. WHY CANT I COPY AND PASTE THE VERSION NUMBER. BLOODY ARESHOLES . AS I SAID IT IS BLOODY OVERCOMPLEX. AT THIS POINT I AM CONSIDERING GIVING UP ON WHAT IS CLEARLY AN OVERCOMPLEX PIECE OF SOFTWARE THAT REALLY DOESN'T LOOK GOOD EITHER AND THERE IS NO OFFICIAL SUPPORT SO WILL HAVE TO LOOK FOR AN ALTERNATIVE. COMPLETE WASTE OF SPACE TOO MANY COOKS SPOIL THE BROTH COMES TO MIND THIS IS WHAT WE HAVE HERE

Ich erhalte die Meldung "Nachrichten konnten nicht in die Mailbox-Datei geschrieben werden. Stellen Sie sicher, dass das Dateisystem Ihnen Schreibrechte einräumt und genügend Speicherplatz zur Verfügung steht, um die Mailbox zu kopieren." Speicherplatz ist genügend vorhanden. Bis jetzt konnte ich meine Emails problemlos abholen. Bin erreichbar über Telefon [edited] oder Handy [edited phone#'s from community support forum]

Running Windows 11 and TB 150.0.2. Can't recall exactly what I did, but after clicking on an email all unread emails are no longer in boldface. Any way to restore them? (New emails that come in are in boldface.) Thank you, Joel Hornstein jobby@att.net