Most useful addons for my use. Note: few addons, that are not available on addons.mozilla.org: thunderbird indicator :: provides mail indication using dbus & envelope.
Organize your schedule and life's important events in a calendar that's fully integrated with your Thunderbird email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.
Collector's Note For calendar support. Developed by Mozilla.
Adds some tools to import and export folders and messages
This addon provides a conversation view for Thunderbird, grouping messages together and allowing you to reply "inline" thus providing a more efficient workflow.
The latest version is compatible with Thunderbird 24+ only (see below for details).
Collector's Note gmail like UI
Switch the signature on/off or choose a new one from your predefined set...
A system tray extension for linux, allowing to set up custom icon, hiding to tray instead of closing, display the number of unread messages in mailing applications, and other features ...
For IT admins who want very much to click through thousands of self-signed certificate warnings and get MitM attacked, this simplifies the process.
Development was discontinued, for details please read "About"