Rated 1 out of 5 stars

by Mr. Bob on April 9, 2018 ·

Locate this folder:
C:\Users\YourName\AppData\Roaming\Thunderbird\Profiles\xxxxxx.default

within the xxxxxx.default folder created a folder and call it chrome

open the chrome folder and add a new text document and name it userChrome.css

now open userChrome.css with notepad

paste the following code exactly:

/*
* Do not remove the @namespace line -- it's required for correct functioning
*/
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

/*
* Make all the default font sizes 12 pt:
*/
* {
font-size: 12pt !important;
font-family: Arial !important;
}




Note: change the font size and font family to your liking
Note: you must restart Thunderbird for changes to take effect.