Correctly wrapping lines

mailnews.wraplength 0
mail.compose.wrap_to_window_width true
plain_text.wrap_long_lines true
view_source.wrap_long_lines true


Setting the User Agent

Open the file: ~/Library/Thunderbird/Profiles/xxxxxxxx.default/prefs.js
Add this line: user_pref("general.useragent.override", "");