Most Popular Extensions
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.
Header Tools Lite Requires Restart
Allows to modify the header and the source of messages
The first and only download manager/accelerator built inside Firefox!
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.
Lightbird Requires Restart
Standalone calendar UI for Lightning
P7MON Requires Restart
Abilita la gestione alternativa degli allegati P7M
ThunderBirthDay Requires Restart
Display birthdays from the Thunderbird addressbooks as events in Lightning.
Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.
FireFTP Requires Restart
FireFTP is a free, secure, cross-platform FTP/SFTP client for Waterfox which provides easy and intuitive access to FTP/SFTP servers.
Check out my new project, FireSSH!
Extra Format Buttons Requires Restart
Adds a font size (in pixels), strikethough, subscript and superscript buttons to Thunderbird's Compose Window.
Saved Password Editor Requires Restart
Adds the ability to create and edit entries in the password manager.
Image Zoom Requires Restart
Adds zoom and rotation functionality for images...
Speed Dial & Start Page with flexible layout for fast access to sites via visual bookmarks
A fork of PDF.js with support for SeaMonkey 2.49.x.
Flexible Identity Requires Restart
Selects an identity based on the recipients list when sending an email
GNOMErunner Options Requires Restart
Allows to customize GNOMErunner theme
SeaMonkey Debug and QA UI Requires Restart
Provides Additional Debug and QA UI for SeaMonkey development and testing.
Return Receipt Toolbar Button Requires Restart
Allow you to add a Return Receipt button to mail compose window toolbar.
This Addon simply adds a dropdown button that lets you download YouTube Videos in various Formats. Download YouTube Videos in FLV, 3GP, MP3, MP4, 720p, 1080p in a single click.
Simple Locale Switcher Requires Restart
An easier management of the user interface language