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QuickFolders (Tabbed Folders)

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 (190)
13,828 users

ReminderFox Requires Restart

ReminderFox displays and manages lists of reminders and tasks. ReminderFox uses easy-to-use lists with warnings/alarms to remind you of all your important appointments.
Synchronize ReminderFox with other calendars as well.

Rated 4 out of 5 stars (550)
2,528 users

Stationery Requires Restart

Extension to mimic Outlook Express Stationery.
Allow you to use HTML files as templates for mail. Also allow custom template in replies or forwarded mail!

Rated 4 out of 5 stars (168)
853 users

Ukrainian dictionary

Ukrainian (uk-UA) spellchecking dictionary

Rated 5 out of 5 stars (58)
9,168 users

General Catalan dictionary

Free Catalan (general version) spelling dictionary.

Rated 4 out of 5 stars (40)
11,054 users

AutoProxy Requires Restart

Are you concerned about your privacy? Or, are you blocked from some websites by a firewall? And, are you arming yourself with a proxy? In that case, AutoProxy is designed for you! A tool to help you use your proxy automatically & efficiently.

Rated 4 out of 5 stars (409)
5 users

Japanese (ja) Language Pack

Japanese (ja) Language Pack

Rated 3 out of 5 stars (3)
45,784 users

StartupMaster

Asks for the master password at startup (fixes multiple password prompt)

Rated 4 out of 5 stars (309)
180 users

Silvermel Requires Restart

A Creamy Silvery Experience

Rated 5 out of 5 stars (534)
31 users

Metal Lion Sea Monkey Requires Restart

Metal Lion meets SeaMonkey.

Rated 5 out of 5 stars (10)
133 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)
879 users

Keep in Taskbar Requires Restart

A simple plugin that makes the Close button behave exactly like the Minimize one.

Rated 4 out of 5 stars (33)
844 users

ThunderPEC Requires Restart

ThunderPEC semplifica la gestione della Posta Elettronica Certificata (PEC) e delle comunicazioni PCT e FatturaPA in Thunderbird.

Rated 4 out of 5 stars (38)
338 users

Canadian English Dictionary

For some reason, Mozilla doesn't have a Canadian localization team, but I know that even the British dictionary doesn't quite cut it for the truly patriotic.

Rated 4 out of 5 stars (82)
8,737 users

Emoji

Add emojis to your e-mails.

Rated 4 out of 5 stars (64)
22,953 users

Telify Requires Restart

Converts telephone numbers into clickable links for use with CTI applications, SIP clients, Skype, Netmeeting, snom phones, the AGFEO TK-Suite Client and SerVonic IXI-PCS.

Rated 3 out of 5 stars (57)
1 user

Addressbooks Synchronizer

Synchronizes selected addressbooks with other instances of thunderbird
using local files, webdav servers or imap servers

Rated 4 out of 5 stars (81)
24,573 users

Monterail Requires Restart

Monterail TB theme with official icons from Monterail

Rated 5 out of 5 stars (28)
10 users

German Dictionary, classical spelling standards

German Dictionary according to the classical spelling standards for spell-checking in Firefox and Thunderbird

Rated 5 out of 5 stars (20)
8,859 users

LightningButton Requires Restart

Toolbar-Buttons for Lightning; advances the feature to get rid of the tabbar.

Rated 4 out of 5 stars (23)
2,763 users