How to adjust the font size of the message list and of the folder list in Thunderbird?

In Windows 10, I use Thunderbird 78.11.0 (32-Bit) as an e-mail client.

Today, suddenly the font size of the message list and of the folder list has become very small. (No changes in other applications).

How can I adjust the font size of the message list and of the folder list in Thunderbird?

Solution 1:

Open the Menu and go to Preferences > General. Scroll all the way down and at the very bottom, click the Config Editor... button (accept the warning).

You're looking for layout.css.devPixelsPerPx, you can just search 'pixels' and it'll show up.

Click on layout.css.devPixelsPerPx and edit the default value of -1.0 to a scale factor you are comfortable with (example: 1.5, 2.0, 2.25, etc).

Clicking OK will allow you to immediately see your changes so you can dial it in pretty easily.