Here is how to change the fonts used in the UI for Thunderbird and Firefox.
See:
- http://www.mozilla.org/support/thunderbird/edit
- http://kb.mozillazine.org/Font_settings_in_Thunderbird
- http://kb.mozillazine.org/Pane_and_menu_fonts
- http://eriwen.com/css/tweaking-thunderbirds-chrome/
Create a userChrome.css file:
- in Thunderbird, create in ~/.thunderbird/<profile>/chrome/
- in Firefox, create in ~/.mozilla/firefox/<profile>/chrome/
You may need to create the chrome directory in Thunderbird.
Example contents are at urls above. e.g. to set the global font size:
/* set default namespace to XUL */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
/*
* Set all the default font sizes:
*/
* {
font-size: 11pt !important;
}