My favourite Thunderbird plugins
- Enigmail
https://addons.mozilla.org/de/thunderbird/addon/71: OpenPGP encryption and signing
- German Dictionary
https://addons.mozilla.org/de/thunderbird/addon/3077: for spell checking mail
- Quote Colors
https://addons.mozilla.org/en-US/thunderbird/addon/quote-colors/: Nicer look of different quote levels
- Lightning
https://addons.mozilla.org/de/thunderbird/addon/2313: Calendar Manager, plugin version of Mozilla Sunbird
- Google Calendar
https://addons.mozilla.org/en-US/thunderbird/addon/google-contacts/: Show contacts from Google calendar
My favorite Thunderbird user.prefs and config settings
- Define additional header
- user_pref("mail.compose.other.header", "Foo,Bar");
- Cycle animated images only once
- image.animation_mode = once
- Include date in header of quoted mail
- mailnews.reply_header_type = 2