Unfortunately, the message list often uses a black font on a dark background. here the screenshot with a bold black font (unread) and here the one with a standard black font (read), where nearly anything is readable.

In particular the unreadblack font on dark background makes it unreadable.

here the screenshot for the issue.

re : I have enabled the Thunderbird dark mode.

I'm assuming you use Windows OS. What computer setting have you set up for apps ?

• In Windows search type: Settings
• Select 'Settings'
• Select 'Personalisation'
• Select 'Colours'

'Choose your colour'

• click on the drop down and select 'Custom'

'Choose your default app mode'

• Select 'Dark'

You should see an example at the top of that window and it should show 'Sample Text' using white font on dark background.

Where it says 'Choose your accent colour' Whatever colour you choose may get used for titles and buttons in Thunderbird depending upon some settings.

Confirm you have the 'dark' settings for apps.

In Thunderbird

Click on the menu app icon (3 lines) select 'Addons & Themes' Select 'Themes' By default there will be 'System theme', 'Light' and 'Dark' You have selected 'Dark'

Have you installed another theme ? If yes, you need to remove any theme you have installed. It's not enough to be disabled. Please click on the 3 dot icon on the right side of the theme and select 'Remove' Then exit Thunderbird. Wait a few moments for background processes to complete and then restart Thunderbird.

re : I have enabled the Thunderbird dark mode. I'm assuming you use Windows OS. What computer setting have you set up for apps ?

• In Windows search type: Settings
• Select 'Settings'
• Select 'Personalisation'
• Select 'Colours'

'Choose your colour'

• click on the drop down and select 'Custom'

'Choose your default app mode'

• Select 'Dark'

You should see an example at the top of that window and it should show 'Sample Text' using white font on dark background. Where it says 'Choose your accent colour' Whatever colour you choose may get used for titles and buttons in Thunderbird depending upon some settings. Confirm you have the 'dark' settings for apps.

yes, I have done this

In Thunderbird Click on the menu app icon (3 lines) select 'Addons & Themes' Select 'Themes' By default there will be 'System theme', 'Light' and 'Dark' You have selected 'Dark'

Yes, dark or System-Theme auto Thunderbird 128.3 or 128.4

Have you installed another theme ? If yes, you need to remove any theme you have installed. It's not enough to be disabled. Please click on the 3 dot icon on the right side of the theme and select 'Remove' Then exit Thunderbird. Wait a few moments for background processes to complete and then restart Thunderbird.

Yes, I installed other themes before and I removed them now.

Unfortunately nothing changes, still black font on dark background.

The problem happens in the following views: Table View in Thunderbird 128, in particular to saved searches, but also to some standard folders. (no matter if Windows 10 or Windows 11)

It also happens in Troubleshoot mode without add-ons. Moreover the black font to dark background also applies to tags, however here the background is not so dark as in the message list, hence it is barely readable. It does not happen: to cards view. I got several Thunderbird 128 instances running (each with different profile folders). On one of them I got many "black font on dark background messages", on the other only a few.

To my understanding I can modify colours only for message content but not for the message lists.

Finally I found out the solution.

The black font on dark background during dark mode was caused by a message filter that assigned a tag with a black font color Messages without a tag correctly obtained a white color. Changing the color of the tags fixes the issue.

One should choose a color that is visible in both day and night mode and this is sometimes difficult.