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CloseReview for Theme Font & Size Changer for ThunderBird by SSRREEDD
Rated 5 out of 5 stars
ATTENTION to users of TB 68 or newer. For your custom styles to work you need to set " toolkit.legacyUserProfileCustomizations.stylesheets" preference setting in "Options/Options/Config Editor..." to TRUE. (And you do not need this extension if you know CSS a bit.)
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