Minimum font size: it's useful to choose a minimum font size if you sometimes receive HTML-formatted messages where the sender uses a font size that's too small on your monitor.Font sizes are set separately for "Proportional" (variable width) and "Monospace" (fixed width) fonts.Using the "Serif" and "Sans-serif" pulldown menus, you can choose the specific fonts (Times New Roman, Arial, etc.) that you want to use for each font style. Using the "Proportional" pulldown menu ( screenshot), you can choose either "Serif" or "Sans-serif" as your default variable width font.For example, you might receive some email encoded with western charset=ISO-8859-1, and some news feeds encoded with unicode charset=UTF-8. Use menu "View -> Character Encoding" to uncover the language group and charset of an individual message. Thunderbird determines a message's language group from its charset (character encoding).(Thunderbird 3beta does not, so: For Unicode messages (UTF-8), set "Fonts for" to the language group named "Other languages". Thunderbird treats Unicode messages (for example, UTF-8) as being in the same language group as your system. Ensure that the "Fonts for" choice at the top of the dialog is set to the language group that you want to change.
Font and font size ("Tools -> Options -> Display -> Formatting -> Fonts."):.Text format ("Tools -> Options -> Display -> Formatting"): if you don't like viewing plain text messages using a fixed width font, this is where you can change it to use variable width instead.
Linux and Mac OS X users, see Menu differences in Windows, Linux, and Mac. On Windows, these settings are accessed in Thunderbird via "Tools -> Options -> Display". Settings via the Options/Preferences dialog A message's character encoding is also known as its charset. E.g., if you send a plain text message containing Japanese characters, you won't want to use a "Western" character encoding because the Japanese characters won't get sent properly. Character encoding-most likely you won't need to worry about this unless you send/receive plain text messages in more than one language.Serif is the default variable width font style in Thunderbird, but you can change it to sans-serif if you prefer. A font's character width is also known as its spacing.
Traditionally, plain text messages are viewed in a fixed width font, but you can set Thunderbird to use a variable width font if you prefer. E.g., "i" and "l" are not narrower than "w" and "O", as they would be in a variable width font ( visual examples). fixed width (monospace)-in fixed width fonts, all characters are the same width.