Add-ons

Provider for Google Calendar by Philipp Kewisch

Allows bidirectional access to Google Calendar

Remove Duplicate Messages by Eyal Rozenberg

Search and remove messages which are the same as other messages in your mail folders (referred to as duplicates or dupes).

CompactHeader by jmozmoz

Add symbol in header plane to switch between compact and expanded view. Work only for Thunderbird 68.0 and older. Currently, there are no plans to update this for newer versions.

Collector's Note Provides more screen real estate for the meat of the message!

QuickFolders (Tabbed Folders) by Realraven (Axel Grude), Alexander Malfait

The "Swiss army knife" of folders. Turn your favorites into tabs - open folders and subfolders, move mails without scrolling around or searching. powerful + easy.

See new mail at a glance after automatic filtering - supports quickFilters addon!

Calendar Tweaks by DW-dev

Allows several tweaks to the Thunderbird/Lightning calendar user interface including new selection styles and repeating event icons. Mimics the colors and styles found in MS Outlook.

Collector's Note Inching (or centimetering) our way to a more complete and efficient Lightning Calendar

Google Calendar Tab by Bryan Clark

Adds the Google Calendar web interface as a new tab directly into Thunderbird. Creating and viewing events works just as it would in a browser like Firefox

Toolbar Buttons by Button Guy

Adds toolbar buttons to the customize toolbar window in several programs including Firefox, Thunderbird and SeaMonkey. Some of the buttons make commonly preformed actions quicker, others add new functionality.

Edit Email Subject (EES) by jisse44, John Bieling

This module allows you to change/edit email subjects

Collector's Note Change those annoying empty or changed subjects that break threads!

Folder Pane View Switcher by Jonathan Kamens, Arnd Issler

Folder view arrows; switch to "All Folders" view when hovering during drag & drop; allow user to select which views are enabled or tied to the view arrows.

Address Close Button by 46emak

Adds a Address Close Button to mail compose window.

ThunderBirthDay by ingomueller.net

Display birthdays from the Thunderbird addressbooks as events in Lightning.

Folderpane Tools by chuonthis, Philip Chee

Allows for customization of the folder pane. Accounts can be rearranged and the startup folder can be chosen.

Copy Sent to Current by Günter Gersdorf

Allows to place a copy of sent messages (aka FCC) into the currently active folder or any other folder you choose, when you create the message. Usually the copies are placed into the 'Sent' folder. For replies, you may also move the original message.

Priority Switcher by H.Ogi

Change priority of the received messages from the toolbar button and the context menus...

Keyword Highlight by genta

Keywordhighlight changes color/size/weight of your favorite keywords...