If you're viewing HTML messages, it may be that the font size is embedded within the message.

My suggestion is to go to settings>general and click the advanced tab for font size and set all the font options to what you consider appropriate size. Then look at top of the pane to see whether it shows 'latin' or 'other writing systems. click that dropdown menu and select the opposite and duplicate the settings there. When done, you should be able to click 'latin' or 'other writing systems' and see duplicate settings. click done. That will let you read all messages in your acceptable font size.

Nothing works. Layout.css.pixelsperpx made the box larger. not the font

font setting doesn't change anything