Try this: Tools/Options/Advanced/General/Config. editor, right-click the preference layout.css.devPixelsPerPx, Modify, and set it to 1.25, OK to close Options.

https://support.mozilla.org/en-US/questions/1269361

Thank you so much. I can now see my emails.

did the layout.css.devPixelsPerPx thing and it works.== thanks

There is no "options" under the tools menu on my Thunderbird, which is 68.3.0 for Mac.

There is supposed to be an add-on for font size, but although the add-on page claims it works on 68, when I try to load it Thunderbird tells me it is not compatible.

David Friedman said

There is no "options" under the tools menu on my Thunderbird, which is 68.3.0 for Mac. There is supposed to be an add-on for font size, but although the add-on page claims it works on 68, when I try to load it Thunderbird tells me it is not compatible.

See this for Mac instructions:

https://support.mozilla.org/en-US/questions/1269361#answer-1264274

Thanks. That worked.

Seems unnecessarily complicated for a feature I would expect many users to want.

Yeah, this is kind of silly to be buried so deep in the bowels of the app.

 I notice font usability is often overlooked by app writers a, even though this is the most front facing item  to the user. 

 Sad , aint it ?

ools/Options/Advanced/General/Config. editor, right-click the preference layout.css.devPixelsPerPx, Modify, and set it to 1.25, OK to close Options.

WORKED PERFECTLY.

Thank you thank you thank you! Old eyeballs need the help!

Aw hell. It makes the T-bird structural text (mailbox names, menu items) larger - -but the text IN the message I'm typing in still minuscule! USED to be I could change the font size in the message -- AT the message.... Now... no help...

Elenor said

Thank you thank you thank you! Old eyeballs need the help! Aw hell. It makes the T-bird structural text (mailbox names, menu items) larger - -but the text IN the message I'm typing in still minuscule! USED to be I could change the font size in the message -- AT the message.... Now... no help...

To change the displayed fonts for received and composed message bodies, see this post: https://support.mozilla.org/en-US/questions/1277542

Will not allow me to Uncheck 'Allow messages to use other fonts'. help

Your message above solved the issue of message index font too small.

Thanks.

John