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 (1,847)
7,104,421 users

Provider for Google Calendar Requires Restart

Allows bidirectional access to Google Calendar

Rated 4 out of 5 stars (965)
356,548 users

Session Manager

Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.

Rated 5 out of 5 stars (829)
199,784 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 (231)
99,584 users


UnMHT allows you to view MHT (MHTML) web archive format files, and save complete web pages, including text and graphics, into a single MHT file in Firefox/SeaMonkey.

Rated 4 out of 5 stars (289)
73,569 users

Send Later Requires Restart

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

Rated 5 out of 5 stars (112)
72,829 users

Add-ons Manager Context Menu Requires Restart

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (46)
70,794 users

ChatZilla Requires Restart

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

Rated 4 out of 5 stars (144)
63,028 users

Mail Redirect Requires Restart

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

Rated 4 out of 5 stars (128)
40,349 users

Copy Plain Text 2 Requires Restart

Copies text without formatting

Rated 5 out of 5 stars (94)
23,654 users

QuickNote Requires Restart

A simple note-taking extension.

Rated 5 out of 5 stars (200)
19,233 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 (52)
18,844 users

PlayFlash 32bit Requires Restart

Flash player plugin - unofficial xpi repack for 32bit browsers.
Use when official plugin installer is not suitable.
All binary files are copyrighted by their authors and distributed for free.

Rated 5 out of 5 stars (21)
13,222 users

Diagnostics for Adblock Plus

Diagnostics tool for Adblock Plus, provides some insight into internal processes of Adblock Plus.

Rated 3 out of 5 stars (4)
12,971 users

Mouse Gestures Suite Requires Restart

Mouse gestures for SeaMonkey & Firefox: navigate & execute commands using mouse gestures (with single mouse button) and rocker gestures (by pressing 2 mouse buttons). Also: scroll wheel navigation, page scrolling, tab scrolling.

Rated 5 out of 5 stars (60)
11,147 users

Highlighter Requires Restart

Quickly highlight some text in Thunderbird message composing windows.

Rated 4 out of 5 stars (49)
10,960 users

AutoCopy 2 Requires Restart

Copies selected text to the clipboard automatically.

Rated 5 out of 5 stars (76)
10,932 users

FiltaQuilla Requires Restart

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.

Rated 4 out of 5 stars (59)
10,497 users

Copy As Plain Text Requires Restart

Removes formatting from copied text.

Rated 4 out of 5 stars (58)
9,032 users

Quote Colors Requires Restart

Quote Colors allows you to select text and background colors of different quote levels which are applied when reading or printing mail/news messages. Additionally, you can choose between graphical and traditional plain text quoting display mode.

Rated 4 out of 5 stars (45)
5,755 users