tzpush Requires Restart

Z-Sync to Thunderbird Addressbook
Will sync Thunderbird address book to Zentyal, Zarafa, Horde and outlook.com/hotmail.

CALDAV - Search/Subscribe Requires Restart

Add CalDAV search & subscribe feature to Lightning

ThunderKeep Requires Restart

Google Keep for Thunderbird

Google Chat Tab

Open Google Chat in a Thunderbird Tab

folderplus Requires Restart

This extension adds some basic missing features about folders.
Move mails to their conversation folder. Navigate to folder with new keyboard shortcuts.

Profile Folder Button

Adds profile folder/directory button.

TB Reset Quote Header Extension Requires Restart

You can now modify the look of the quote header on replies. Quote header templates are included in the xpi ( open the xpi with a archive program like winzip and extract the two txt files) Then, in the extension's options page, type the word...

ScrollToNext Requires Restart

Use your mouse-wheel to select the next message by placing the mouse over the right hand side of the message list pane and then scrolling.

Addressbooks Default Search

Provides ability to set default search query for address books.

TorBirdy Requires Restart

This extension configures Thunderbird to make connections over the Tor anonymity network.

Fritz!BoxDial Requires Restart

Expiry Timestamp Requires Restart

Set expiry timestamp for the message(s) and manage them.

Delete Trash Button Requires Restart

Adds an Empty Deleted button to the Toolbar

Get All Senders

This add-on retrieves all the senders associated with the emails in this mailbox and stores them in your clipboard.
For more information and to report an issue, please visit the project home page at https://github.com/CicadaCinema/get-all-senders .

Compose for Thunderbird Requires Restart

THIS ADDON IS UNMAINTAINED, SEE BELOW.

Compose messages the new hip way! Allows you to compose in a tab with a new editor and an improved autocomplete.

Version Number in Add-ons Manager

[Restartless] [e10s Compatible]
Easily viewable version info in the Add-ons Manager on Firefox/Thunderbird 41.0 - 56.*
Also restores the add-on version number on Firefox/Thunderbird 41.0 - 56.*.

XPCOMViewer Requires Restart

XPCOMViewer is tiny tool for exploring XPCOM components.

Montezooma Requires Restart

Montezooma is a Thunderbird Addon that adds zooming functionality to windows.

MailClassifier Requires Restart

The mailclassifier extension helps you to move the email in the right folder, it uses multi-level bayesian filtering...

Quick Locale Switcher Requires Restart

Allows you to quickly switch to a different language (User Interface, Spell Checker Dictionary and Website content) in your Mozilla application.