Thunderbird add-ons that I've either used for years, or tested and highly suggest.
Note from Mozilla: This add-on has been discontinued. Try MinimizeToTray Revived instead.
Minimize applications to the system tray.
Adds many new mail filter actions - launch a file, suppress notification, remove star or tag, mark replied or unread, copy as "read", append text to subject.
This addon adds month tabs into Lightning calendar month view
custom additions to Stylish extension.
brings back features from 0.5.9 and adds new features
I can't be bothered to change SC, so amo will allow it to be uploaded
Adds a summary of mail accounts and folders to replace the account central pane and the empty folder preview
Zoom in, zoom out, and reset zoom with one toolbar button. Works in the Compose window too.
The main goal allows users to open (and in some cases edit) page source with external applications.
Maximize message pane by collapsing the thread pane. You can read a message in larger area without opening a new message window...
(Formerly Local Install) The primary goal of this extension is to provide the tools needed to install and manage extensions and themes locally and tons of other features.
Note: With Toolkit 6.0 Auto Archiving is fully working in Firefox 2.0 and temp...
This add-on provides a follow-up email feature for Thunderbird.
This add allow to customize the snooze delay when snooze popup appears (lightning required).
Adds a new action to mail filters to allow playing a particular sound when the filter matches. Also includes several sample sound files.