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.
Simple Locale Switcher Requires Restart
An easier management of the user interface language
Enhanced Priority Display Requires Restart
Enhanced thread pane display of message priorities.
Restores version numbers for all installed add-ons inside Add-on Manager on Firefox, Thunderbird and Seamonkey.
FireTray Requires Restart
A system tray extension for Linux and Windows, allowing to set up custom icon, hiding to tray instead of closing, display the number of unread messages in mailing applications, and other features ...
Dorando keyconfig Requires Restart
A modified Dorando's addon to rebind keyboard shortcuts. It is designed to be a drop-in replacement, keeping your old settings. (See details for upgrade instructions.)
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!
Add-on for Thunderbird that replaces the built-in notifications with OS native ones. It supports most Linux Desktop Environments as well as Windows 8.1/10.
ThreadKey Requires Restart
Strike the 'T' key to sort messages by thread, strike the 'U' key to sort them unthreaded again, just like the 'G' key switches to Grouped By Sort view
Block advertisement and access to adult sites
SeaTab-X-2 Requires Restart
Adds Firefox-style tab closers into SeaMonkey.
FolderFlags Requires Restart
Allows users to edit the flags Thunderbird sets on folders.
Display Mail User Agent Requires Restart
Displays icon for user agent of received mails.
IMAP Received Date Requires Restart
Make the “Received” column in IMAP folders show when messages were actually received.
Custom Buttons Requires Restart
Gives a possibility to create custom toolbarbuttons...
Adds buttons to toggle the using the default page colors and fonts, and the page defined colors and fonts.
Scriptish Requires Restart
The greatest user script engine on the Internet (a fork of Greasemonkey).
Joomla! Admin Requires Restart
Joomla! Admin brings ease & convenience to your computer/workstation, by providing you with a ready-to-use menu options that balms your repetitive work :) Now, Go to the Administrator page or Duplicate the current tab to a new tab/window in a jiffy!!
CheckBoxMate Lefedor Edition Requires Restart
Check multiple checkboxes by drawing a rectangle around them. FF6 version.
I've made this version since i did need it for use with RTM,