I just updated to the latest version of Thunderbird after not updating for well over a year now, so I'm late to the "hate on Thunderbird devs" party. The font changes, as I'm sure have been mentioned a million times, is a disaster. I've already wasted several hours on this. I managed to fix the core font size issue with, which fixed MOST of the problems: layout.css.devPixelsPerPx = 1.12 However, I can't figure out how to increase the row height of the message area. If I switch from Compact mode to Default, everything in the folder pane gets far too big (and, yes, I reset devPixelsPerPx as a test) and the message area rows are too tall. In addition, I want a few pixels at the bottom of the message area so that when a new message comes in, I see a few pixels of the top of the new message without having to scroll. If you are having trouble visualizing what I want: Per row of each message: 1px padding at the top + 18px main area + 1px padding at the bottom (i.e. 20 px total). After the last row: 3px (or so) to display just enough pixels to show the next message whenever it arrives. Using the browser toolbox, I see that the height of each row is defined using an inline style. So I can't apply CSS to fix it globally in a custom stylesheet. Using the Inspector, I can temporarily change the inline style of a single row to "height: 20px" and it displays the row as I want it to be displayed. However, this doesn't solve the other problem of putting a few pixels at the end of the messages to display a few pixels of a new message when it arrives. I also tried modifying the selector "table[is="tree-view-table"] & td" to hardcode a 20px height and added a 3px padding to the bottom, which works to solve BOTH problems BUT introduces a bug where switching folders no longer scrolls to the bottom of the list of messages. My guess is that Thunderbird is calculating where to scroll to based on the assumption that the row height is exactly 18px. So using CSS alone is not really possible. What a mess.