This was driving me nuts. I’m an old-school Eudora user — version 184.108.40.206, you can keep your fancy new open-source Eudora; I love the one I have.
After a recent Windows update, all the fonts in Eudora suddenly looked bold…or bigger…something was wrong. And it was annoying the hell out of me. I couldn’t seem to fix it by changing or resetting fonts, no matter how hard I tried.
However, after a little bit of searching on the Internet, I came across a fix for it that worked, and returned fonts back to normal. It was also mentioned that this can be used to return fonts in web browsers back to normal after a Windows update gives you the same problem (I am running Windows 7 64-bit).
It’s pretty simply. Go to the display control panel. Set the resolution to something different than you already have it. Keep the changes. Go back, switch it back to the resolution you want to run at, keep changes again.
This fixed it for me. Good luck!