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Header Tools Lite Requires Restart

Allows to modify the header and the source of messages

Rated 5 out of 5 stars (31)
5,295 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)
5,254 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 (247)
4,756 users

QuoteCollapse Requires Restart

Collapse and expand quotes. Please see the extension homepage for further information.
Note that MozDev has shut down long ago (mailing list etc). Add-On homepage, source code and issue tracker are on GitHub, as linked on this page.

Rated 4 out of 5 stars (27)
3,829 users

P7MON Requires Restart

Abilita la gestione alternativa degli allegati P7M

Rated 5 out of 5 stars (1)
3,821 users

Smiley Fixer Requires Restart

Fixes Wingding Smileys in Outlook-generated emails

Rated 4 out of 5 stars (24)
3,409 users

Toggle Word Wrap Requires Restart

Toggle word wrapping and PRE element wrapping in the message composition and HTML display windows, respectively.

Rated 4 out of 5 stars (47)
3,154 users

Year view Requires Restart

Year view for calendar.

Rated 4 out of 5 stars (50)
2,729 users

FolderFlags Requires Restart

Allows users to edit the flags Thunderbird sets on folders.

Rated 5 out of 5 stars (9)
2,717 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)
2,450 users

No Message Pane Sort by Mouse Requires Restart

No Message Pane Sort prevents accidental resorting of the message pane by disabling mouse button clicks on the column headers.

It is still possible to sort messages by ctrl-clicking the header.

Rated 5 out of 5 stars (31)
2,011 users

FlashGot Mass Downloader Requires Restart Featured

Download all the links, movies and audio clips of a page at the maximum speed with a single click, using the most popular, lightweight and reliable external download managers.

Rated 5 out of 5 stars (889)
1,930 users

Join-NG Requires Restart

Join partial messages. Somewhat similar to MS Outlook Express "combine and decode".

Rated 5 out of 5 stars (4)
1,878 users

Folderpane Tools Requires Restart

Allows for customization of the folder pane. Accounts can be rearranged and the startup folder can be chosen.

Rated 3 out of 5 stars (124)
1,705 users

Awesome ldapInfoShow

Show contact photo and other info from Local Dir, Addressbook, LDAP, Facebook, LinkedIn, Flickr, Gravatar etc

Rated 4 out of 5 stars (11)
1,676 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)
1,644 users

Show InOut

Adds two columns to the list of mails. One shows an indicator wether a mail is incoming or outgoing, the other shows the sender or the recipient of the mail respectively...

Rated 5 out of 5 stars (40)
1,393 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 5 out of 5 stars (50)
1,364 users

CuteButtons

Adds icons to buttons and/or menus.

Rated 4 out of 5 stars (94)
1,361 users

Disable Add-on Compatibility Checks

Reinstates the extensions.checkCompatibility preference without respect to the current application version.

Rated 4 out of 5 stars (120)
1,274 users