Most Popular Extensions

Subscribe

Lightning Requires Restart Featured

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.

Rated 3 out of 5 stars (1,947)
6,518,445 users

ImportExportTools Requires Restart

Adds some tools to import and export folders and messages

Rated 4 out of 5 stars (201)
457,433 users

Enigmail Featured

OpenPGP message encryption and authentication for Thunderbird and SeaMonkey.

Rated 4 out of 5 stars (222)
128,767 users

gContactSync Requires Restart

Synchronizes contacts & groups between Thunderbird or SeaMonkey and Google Contacts. Imports Facebook friends, contacts you follow on Twitter, and more.

Rated 4 out of 5 stars (268)
88,795 users

LookOut (fix version) Requires Restart

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).
Support: Thunderbird and SeaMonkey

Rated 4 out of 5 stars (29)
85,334 users

Send Later Requires Restart

True "Send Later" functionality to schedule the time for sending an email.

Rated 5 out of 5 stars (139)
68,964 users

Mail Merge Requires Restart

Mass Mail and Personal Mail

Rated 5 out of 5 stars (162)
60,385 users

LookOut Requires Restart

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).

Rated 4 out of 5 stars (156)
45,252 users

Mail Redirect

Allow to redirect (a.k.a. "remail") mail messages to other recipients.

Rated 4 out of 5 stars (128)
36,013 users

Addressbooks Synchronizer Requires Restart

Synchronizes selected addressbooks with other instances of thunderbird
using ftp/webdav/imap servers

Rated 4 out of 5 stars (59)
32,568 users

DOM Inspector Requires Restart

DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.

Rated 5 out of 5 stars (77)
26,934 users

ChatZilla Requires Restart

A clean, easy to use and highly extensible Internet Relay Chat (IRC) client.

Rated 4 out of 5 stars (150)
24,753 users

Display Mail User Agent Requires Restart

Displays icon for user agent of received mails.

Rated 4 out of 5 stars (111)
23,548 users

MinimizeToTray revived Requires Restart

Minimizes windows into the system tray.

Rated 4 out of 5 stars (389)
23,456 users

Confirm-Address Requires Restart

Confirm E-mail address before sending mail

Rated 4 out of 5 stars (52)
22,113 users

QuickFolders (Tabbed Folders) Requires Restart

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!

Rated 5 out of 5 stars (125)
20,909 users

SmartTemplate4 Requires Restart

SmartTemplate4 offers an easy way to automatically create customized replies by auto-inserting various mail headers. Templates can be created for every account as well as for the default (all email accounts). Also supports the Stationery Add-on.

Rated 5 out of 5 stars (54)
18,696 users

ReminderFox Featured

ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.

Rated 4 out of 5 stars (532)
16,526 users

JavaScript Debugger Requires Restart

As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.

Venkman is the code name for Mozilla's JavaScript Debugger. Venkman aimed to provide a powerful JavaScript debugging environment for Mozilla based browsers.

Rated 4 out of 5 stars (52)
15,308 users

Theme Font & Size Changer for ThunderBird

Theme Font & Size Changer lets you change the global font size and font family used for the user interface in Firefox. Design your browser with your favorite font.

Rated 3 out of 5 stars (78)
13,760 users