Interface Customizations

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Display Mail User Agent Requires Restart

Displays icon for user agent of received mails.

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

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

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 ...

Rated 4 out of 5 stars (278)
11,878 users

Menu Wizard Requires Restart

Customize menus : Helps removing, moving and renaming menus and menu items
Colorize important menu for ease of use! (use Style (CSS))
Change or disable any of used keyboard shortcuts
Support: Firefox, Thunderbird and SeaMonkey

Rated 5 out of 5 stars (245)
5,890 users

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.)

As of version 2016.2, Custom keys (using custom JavaScript) work again!

Rated 5 out of 5 stars (47)
4,544 users

Simple Locale Switcher Requires Restart

An easier management of the user interface language

Rated 5 out of 5 stars (14)
4,041 users

Classic Toolbar Buttons [Tb24-58] (discontinued)

'Classic Toolbar Buttons' add-on restores old toolbar button ui (known from Fx 4-7 small view, Fx4-12 large view & Tb5-14) for current Firefox, Thunderbird and Seamonkey versions.

Rated 5 out of 5 stars (145)
3,290 users

FolderFlags Requires Restart

Allows users to edit the flags Thunderbird sets on folders.

Rated 5 out of 5 stars (8)
3,147 users

IMAP Received Date Requires Restart

Make the “Received” column in IMAP folders show when messages were actually received.

Rated 5 out of 5 stars (11)
2,331 users

True Full Screen in SeaMonkey

This extension enables true full screen mode in SeaMonkey for HTML5 video players, slide-shows, etc. and also for full screen invoked manually with the F11 key.

Rated 5 out of 5 stars (17)
2,266 users

CuteButtons

Adds icons to buttons and/or menus.

Rated 4 out of 5 stars (94)
1,682 users

ThreadKey

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

Rated 4 out of 5 stars (23)
1,420 users

SeaTab-X-2 Requires Restart

Adds Firefox-style tab closers into SeaMonkey.

Rated 5 out of 5 stars (22)
1,287 users

Enhanced Priority Display Requires Restart

Enhanced thread pane display of message priorities.

Rated 5 out of 5 stars (7)
1,085 users

Speed Start

Speed Dial & Start Page with flexible layout for fast access to sites via visual bookmarks

Rated 5 out of 5 stars (80)
765 users

Text2Link Requires Restart

Text2Link is a simple and easy-to-use way to copy the text of a link, or to open URLs and send emails to addresses not marked-up as HTML links.

Rated 4 out of 5 stars (41)
638 users

GNOMErunner Options Requires Restart

Allows to customize GNOMErunner theme

Not yet rated
614 users

GNotifier

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.

Rated 5 out of 5 stars (48)
609 users

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,

Rated 4 out of 5 stars (16)
590 users