I don't think you can change the folder list font. For the message list
font, click View>Arrange By>Current View>Customize Current View and select
the "Other Settings" button. That will allow you to change it for the
current folder. If you want to change it for all folders that use the same
view, use "Define View" instead of "Customize Current View", select the view
you want to change, and click Modify, then the "Other Settings" button.