Configuring Thunderbird Reply Header

The default reply header can be customized if you create the file user.js in the profile directory of your Thunderbird home (if you have Windoz, look inside the Doc&Settings/AppData/Thunderbird or something like that) and fill it with the following:

// Change the reply header
// 0 - No Reply-Text
// 1 - "[Author] wrote:"
// 2 - "On [date] [author] wrote:"
// 3 - User-defined reply header. Use the prefs below in conjunction with this:
user_pref("mailnews.reply_header_type", 3);

// If you set 3 for the pref above then you may set the following prefs.
user_pref("mailnews.reply_header_authorwrote", "%s said the following");
user_pref("mailnews.reply_header_ondate", "on %s");
user_pref("mailnews.reply_header_separator", " ");
user_pref("mailnews.reply_header_colon", ":");
// The end result will be [authorwrote][separator][ondate][colon]