Hey there, does someone have an idea? Is this a bug that background color can't be changed although other email clients can do it?

I really do not know how to explain this to you, and apparently neither does anyone else. Hence the failure of you to get a reply.

This image shows a table. with the text in one cell of the table and the other used to set major borders and background colors. These are the sorts of things web page (HTML) have been doing since the literal invention of the table as a feature of HTML as there is no absolute typographic controls in HTML. to set this stuff like there is with a printer and paper.

So you are asking about a highly configured and featured web page any applying simplistic typing concepts to it. The result is not what you want because the product is not what you think it is to begin with.

This excerpt from your image clearly shows the background of the page to be set to white (with black text) so the question then becomes how is the color being controlled. The answer is probably a custom cascading style sheet that sets the color without using the background tag for the entire HTML page. There is an example of that style of coding here https://stackoverflow.com/questions/31760899/how-to-add-more-specificity-to-css-class-background-color-blue-so-it-overrides

Introductory information on CSS can be found here https://en.wikipedia.org/wiki/CSS Is it a bug? I would not consider it one. Is it inconvenient. It can be. Would it be better if Thunderbird exited all preexisting CSS before replying. Probably. Is there an enhancement request for such a thing outstanding. Also probably as it can be inconvenient and the use of CSS in HTML is very nearly 30 years old so the issue is not a new one (CSS published December 17, 1996), but I really do not have the interest to search the bug system to find out for sure. You are welcome to look for yourself however. See https://bugzilla.mozilla.org/home

Hi Matt,

don't you think Zendesk is a frequently used ticketing system? I notice that not all Zendesk-Emails have those dark background maybe dependend on senders settings, then it's fine and I can write an answer. But a lot have. I started this issue because other clients like M$ Outlook or even Open-Xchange manage it to set a white background color when answering on those emails. Exactly this is the moment I'm so much disappointed from thunderbird (there're a lot of other annoying things...) although I'd like to have more open-source in the world and I like mozilla, I use for more than 20 years.

What would you do if you need to answer such an email from ticketing system with dark background? The only poor idea I have for thunderbird is to draw a new table cell at the top of the answering email, set a white background and start typing there.

Now I checked the source code of one of the emails and find:

<style data=3D"cr/theme">=0D /*=0D $color-Main_background: #F1F5F7;=0D $color-Outer_text: #082137;=0D $color-Content_background: #FFFFFF;=0D $color-Text: #082137;=0D $color-Background_misc: #cccccc;=0D $color-Links: #1155CC;=0D $slider-Maximum_width: 800px;=0D =0D

Or even in other emails like Hermes parcel service:

       <style type=3D"text/css">
           body {
               background-color: #F3F3F3 !important;

Yes, maybe it's not easy to modify those css background-color - tags but other clients can do it. Wouldn't it be great if Thunderbird could do it, too?