Rated 5 out of 5 stars

yazan: okddcode tarih: Nisan 22, 2020 ·

Solution to zoom everything (was already previously posted):

Instead of using TF&SC (currently for TB 60 and lower), try this:
≡ > Preferences > Preferences > Advanced > General > Config Editor > I accept the risk! > search for "layout.css.devPixelsPerPx", modify value to "1.5" which is equal to 150%.

now close the settings and profit ;-)

Rated 5 out of 5 stars

yazan: okddcode tarih: Kas. 27, 2019 ·

Thank you very much Trenton!
Your workaround helps a lot to scale up the font size of plaintext e-mails.

@J. Winters you can even enter a value below 1 to scale down the font size (example: 0.5)

permalink of the workaround:
https://addons.thunderbird.net/en-US/thunderbird/addon/theme-font-size-changer-fixed/reviews/1158832/