Thunderbird Community Forum

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.

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

When I tried to delete my old password in "Show Passwords" by highlighting my old password and hitting the backspace key to delete it and every time I click on the background or hit "Enter", it just pops back on where it was so I couldn't correct it without having to click "Remove all" which turned off the "Show Passwords" in "Saved Passwords".

I have been unable to send emails for several weeks and keep getting the following error message: sending of message failed The message could not be sent because connecting to the outgoing server (SMTP)smtp.1und1.de failed. The server may be unavailable or is refusing SMTP connections. Please verify that your outgoing server (SMTP) settings are correct and try again.

My settings have not been changed so I am wondering what has changed and how i can correct it. My computer knowledge and ability is very limited so please bear theis in mind when offering advice and solutions. Thank you.

When I got into the "Show Passwords" in "Saved Passwords in "Privacy & Security", I had to click "Remove All" in "Show Passwords" to delete it, and now it turns off the "Show Passwords" in the "Saved Passwords" section, and now the OAuth2 is missing.

I would appreciate detailed instructions on how to transfer emails currently in my "roundcube" email account to my mozilla thunderbird emal account (I would like to have my old emails transported to the mozilla account).

I have Thunderbird mail access on my work place, with 1000 mail and 300 send mail its very important recorded for my usage but disk space is full however i have to could not send any mail it show mail full

I want to use thunderbird on a Windows 11 laptop. Tell me how to connect Thunderbird to send and receive emails from email account, jds@sefcik.net, hosted at smartmail.buz.net.

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.

Hello,

I have been using Thunderbird only occasionally for backing up Google emails after which I delete the emails from Google. I am thinking of using Thunderbird permanently but there are things I'm not sure about.

1). Does Thunderbird automatically integrate Google Take Out mbox files automatically into one email list? When I start Thunderbird, I see files that I have uploaded to Thunderbird (on two occasions in the past and these were mbox files from Google Take Out) but these files are empty. (screenshot attached). When I select the "all mail" folder all of the mails saved since 2005 appear to be there.

2). Does Thunderbird save attachments or only the emails themselves?

I would be grateful for some help so that I can optimise my working with Thunderbird.

Best wishes

DanZ

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.

Attempting to install Thunderbird on an additional desktop using same address as my original computer has. But when I attempt to install on computer #2, Thunderbird doesn't recognize my email or password from computer #1.

well installed Thunderbird on UBUNTU 24.04 LTS doesn't start beyond choice of new profile and selection of old data file from a former UBUNTU installation (UBUNTU 25.10 ) I retrofitted to current UBUNTU 24.04 LTS , thus more stable

Hi, I use thunderbird as both POP and IMAP through gmail. I keep all my emails on my POP thunderbird desktop client. I use IMAP on my thunderbird laptop client, iPhone, iPad via Apple mail when remote, then download the emails to my desktop.

What I want to do is read emails and set them to archive on my IMA laptop, iPhone, iPad. I know Gmail tags the archived emails. How do I stop thunderbird from downloading the archived emails to my POP thunderbird desktop client?

Thanks! Art

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, Thunderbird has already imported my Hotmail account. How do I import my Outlook.com account? It was offered to me the first time, to add another one but for some reason, I could not. Thanks

Send Message Error "Sending of mmessage failed. An error occured while sending mail: Outgoing server SMTP error. The server responded [192.1680.166] Helo command rejected: IP address 204.237.106.179 Blocked due to Abusive Authentication Behavior."

Problem recently developed. So far on 2 different addresses but could be more. Additional info, hotmail and gmail accounts sending work OK; xplornet.com account is the problem interface but the C/Svc folks say it's a Thunderbird mail issue.