When I receive some special html formatted email e.g. from ticket system like Zendesk they look like this: https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2025-06-17-01-06-32-c4ca42.png When I want to reply to the text stays at the blue colored background and the text would be hard to read and it looks ugly: https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2025-06-17-01-06-37-c81e72.png Unfortunately I can't change background color to blank or white in Tunderbird 139.0.2. In menu of reply window "Page colors and Background", "Use custom colors", "Background" I can set to #ffffff of course, click apply and ok, but that doesn't change it: https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2025-06-17-01-06-42-eccbc8.png I suppose it relies to the html formatting of the received email because on starting to write a complete new email it works. But that's very annoying that Thunderbird doesn't manage to change background colors on already formatted html body. Is this a bug or only poor source code and the programmer didn't have much motivation to write and robust code which could gather all html emails? Could you check with this test email to test and reproduce? [https://limewire.com/d/pqbEk#1idjNje6b2 https://limewire.com/d/pqbEk#1idjNje6b2] Thanks a lot! I'd be very happy about your help.