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.
LookOut is a plugin which allows Thunderbird to interface with Microsoft's mail tools by decoding metadata and attachments encapsulated/embedded in a TNEF encoded attachment (aka winmail.dat).
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 38+ only (see below for details).
Quicktext is an extension for Thunderbird that lets you create templates that can be easily inserted into your own emails.
German dictionary igerman98 (de_DE, Germany), for Firefox, Thunderbird und Seamonkey.
Did your friend send you a cool link? Want to read the rest of that interesting article? Don't want to open up your web browser just to view it? You don't have to! Just view it in Thunderbird with ThunderBrowse!
Add symbol in header plane to switch between compact and expanded view. Options to switch between one or two lines compact view, which buttons should be displayed in header pane. For Thunderbird 36 and older use version 2.0.9 (see version history)
It adds a button that can be put in toolbars and that open the addressbook in a new tab
View the most important e-mails sorted after specified resubmission date and filter them. Do the same with sent e-mails to see which recipient has to be reminded to answer your e-mail.
Only tested on Windows!
Some bugs not fixed yet!