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Thunderbird 139: Reply composer uses black text on black background with dark theme

  • 2 replies
  • 1 has this problem
  • 11 views
  • Last reply by Toad-Hall

daniele balit
daniele balit
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Hello,

Since updating to Thunderbird 139, I’ve encountered a persistent issue with the dark theme in the reply composer. When replying to HTML messages, the text appears black on a dark background, making it nearly unreadable.

This issue did not occur in Thunderbird 138 — nothing else changed on my system except the automatic update.

Here’s what I’ve tried:

- Verified that toolkit.legacyUserProfileCustomizations.stylesheets is set to true in about:config.

- Created and edited a userContent.css file inside the active profile folder.

- Used various CSS rules targeting messengercompose.xhtml to override text and background colors (e.g. forcing color: #ddd and background-color: #000).

-Tried resetting composition preferences like msgcompose.background_color and msgcompose.text_color in prefs.js.

- Set Thunderbird to use plain text composition, which works — but this is only a temporary workaround.

- Ensured that no conflicting extensions (e.g. DeepDark) are enabled.

-Confirmed the issue happens even with a clean profile. - Manually set the default text and background colors to white on black in the composition settings — but replies still render with black text on black background.

The problem seems to be that Thunderbird 139 overrides the user-defined dark theme or does not apply CSS properly in replies.

Is this a known regression? Is there any workaround to enforce dark-compatible colors in HTML reply composition without switching to plain text?

Thanks for your help.

Daniele

Hello, Since updating to Thunderbird 139, I’ve encountered a persistent issue with the dark theme in the reply composer. When replying to HTML messages, the text appears black on a dark background, making it nearly unreadable. This issue did not occur in Thunderbird 138 — nothing else changed on my system except the automatic update. Here’s what I’ve tried: - Verified that toolkit.legacyUserProfileCustomizations.stylesheets is set to true in about:config. - Created and edited a userContent.css file inside the active profile folder. - Used various CSS rules targeting messengercompose.xhtml to override text and background colors (e.g. forcing color: #ddd and background-color: #000). -Tried resetting composition preferences like msgcompose.background_color and msgcompose.text_color in prefs.js. - Set Thunderbird to use plain text composition, which works — but this is only a temporary workaround. - Ensured that no conflicting extensions (e.g. DeepDark) are enabled. -Confirmed the issue happens even with a clean profile. - Manually set the default text and background colors to white on black in the composition settings — but replies still render with black text on black background. The problem seems to be that Thunderbird 139 overrides the user-defined dark theme or does not apply CSS properly in replies. Is this a known regression? Is there any workaround to enforce dark-compatible colors in HTML reply composition without switching to plain text? Thanks for your help. Daniele

All Replies (2)

Toad-Hall
Toad-Hall
  • Top 10 Contributor
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It sounds like this bug might be causing the issue. https://bugzilla.mozilla.org/show_bug.cgi?id=1967725

Helpful?

Toad-Hall
Toad-Hall
  • Top 10 Contributor
more options

I've just been doing some testing to see if there's short term workaround. I'm using Thundrebird dark theme and also Windows apps set for Dark.

Assuming you have selected to use the new 'Dark mode' option in the Message Pane header area, so you see incoming mail using white on dark....

In Settings > Composition Select 'Use Readers default colours'

This still keeps the background where I type reply as white font on dark background, but it does show the replied message as black on white as per html css as sender intended - but at least it's readible.

You should not need to worry about what the recipient sees because it's possible they will have entirely different settings.

Modified by Toad-Hall

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