Thunderbird Community Forum

I have been using T-bird for years successfully until lately. We have multiple email addresses in Comcast and Gmail, but lately our passwords that we have been using and know are correct because they are written on paper and Keypass, are being changed somehow so that they will no longer work. When we look at the saved passwords in Thunderbird we see some have been changed on a certain date that we did not do, and the password listed now must be about 200 characters long. Then when we go to change the password, it may be listed as changed. Then when we try to send a message with that email address, we get an error message saying, for example, smtp.googlemail.com and a wrong username/address completely. I can find no way to correct the username email in any settings in Thunderbird. I have searched the Thunderbird HELP files many times, but am unable to find any of this addressed anywhere. After trying to fix these problems for most of 3 days now, I have get rid of Thunderbird for an email client that works correctly!!!

Hello,

Despite the fact that I have set Thunderbird to display messages as plain text, my needs are not being fully respected. If the message contains some form of markup, presumably HTML, the font size is not what I have chosen. Generally, the font size is smaller than what I have specified in the Thunderbird settings.

This is unacceptable. It is a usability / accessibility issue. If the user chooses Plain Text and sets a font size, they have done that for a reason. Which is accessibility. If Thunderbird ignores the needs of users and applies styling rules to messages, that is a failure state.

Is there some way to actually, truly, absolutely display all messages as plain text in a specified font, weight, and size? If not, what is the protocol for reaching developers so that they can respond to this issue?

Thank you

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.

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.

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?

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

Mail filters for custom headers like List-Unsubscribe, Authentication-Results or Received-SPF copying messages from IMAP accounts to Local Folders do not work on the Yahoo! IMAP account. For example:

filter1.jpg: name="_Inbox2: List-Unsubscribe <https" enabled="yes" type="17" action="Copy to folder" actionValue="mailbox://nobody@Local%20Folders/Inbox/_Inbox2" action="Stop execution" condition="OR (\"list-unsubscribe\",contains,<https)" (should copy messages from IMAP folders to _Inbox 2 on Local Folders)

filter2.jpg: name="Spam: Authentication-Results dkim=unknown | Received-SPF fail | X-Antivirus-Status Infected" enabled="yes" type="17" action="Copy to folder" actionValue="mailbox://nobody@Local%20Folders/Junk" action="Stop execution" condition="OR (\"authentication-results\",contains,dkim=unknown) OR (\"authentication-results\",contains,dkim=perm_fail) OR (\"authentication-results\",contains,dkim=none) OR (\"received-spf\",begins with,fail) OR (\"received-spf\",begins with,softfail) OR (\"received-spf\",begins with,none) OR (\"x-antivirus-status\",is,Infected)" (should copy messages from IMAP folders to _Inbox 2 on Local Folders)

But filter3.jpg for Subject works well: name="Inbox" enabled="yes" type="17" action="Copy to folder" actionValue="mailbox://nobody@Local%20Folders/Inbox" condition="OR (subject,doesn't contain,t[k\6iq69pd+}'cr)" (copies all remaining messages from IMAP folders to Inbox on Local Folders)

(the snippets above are fragments of the msgFilterRules.dat file)

Filters1 and 2 work well on other IMAP accouns, like for example wp.pl. So this is about Yahoo or something is corrupted. My question is, what wrong is here ? And by the way - how to create filter copying all messages from IMAP to Local Folders ? Is better way then filter3 looking for random string in the subject or somewhere else ? Thank you.