Increase Font size in Thunderbird I have recently purchased an iMac to replace my 13" MacBook Pro and am gradually setting it up.

My eyesight is fading, so I intend to use the bigger screen to improve readability.

One application I am having problems with is Thunderbird. The list of messages in my Inbox remains stubbornly small.

I have tried changing Font size in Preferences/Display to no avail.
Theme Font &amp; Size Changer sometimes disappear from Thunderbird. You simply cannot see the button to the options for this add-on. In order to make Theme Font &amp; Size Changer add-on working for Thunderbird, you need to change the xpi-file (which is basically a zip file) before you import the add-on to Thunderbird.

You need to change the Bootstrap.js file inside the .xpi file. Bootstrap.js is a large file, and you have to comment out a line, rezip the files, and rename the extension from zip to xpi and reinstall the module.

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