Macs seem to have size problems that don't afflict other platforms. I have no idea why these controls are disabled.

But if you are routinely using zoom to enlarge messages to make them readable, I'd suggest another setting would be more useful.

Go to Thunderbird|Preferences|Display|Formatting. Click the "Advanced" button. Set the minimum font size to a suitable value; the values being used for the other font selections will guide you to the sort of value you need here.

At the top is a button labelled "Fonts for:" which yields a drop-down list of available character sets. Review the list for encodings you are likely to encounter. I'd suggest setting it for both "Latin" and "Other Writing Systems".

Hi Zenos,

Thank you for the information. Although the suggested adjustment made my actual email text HUGE, here was no change on the in/out window lists, I appreciate your effort to assist, though.

R

Message lists (Inbox etc) are handled differently. You didn't say that was also of interest.

The usual suggestion for adjusting the UI is to use the Theme and Font Size Changer add-on.

https://addons.mozilla.org/en-GB/thunderbird/addon/theme-font-size-changer/

Note this works in both Firefox and Thunderbird, despite much of the supporting text talking about it as Firefox add-on. Make sure you install it into Thunderbird, not just Firefox.

I prefer to use font settings in userChrome.css (for the message lists) and userContent.css (for message content). I don't know if these have a minimum font size option, but I don't mind having a consistent font size for all content. It does mess up some html-formatted messages.

http://kb.mozillazine.org/index.php?title=UserChrome.css

Yay! Worked great. Thank you!