Hi Please be more specific about exactly where you want to change the font. There are ways to change the font used for viewing an email, creating new emails, while creating a single email, or the whole of Thunderbird's display (Menus, folders, toolbars etc.). As examples of the several places to look - Account settings for the default fonts when composing, Tools/Options - Preferences - Display for viewing emails, or Format at the top of an email you are creating. Thanks, Agnes