A necessarily personal list of preferred Thunderbird extensions

The Mozilla Thunderbird (http://www.mozilla.com/thunderbird) email client (Mac, Windows, Linux) is a very nice email environment for POP or IMAP users. Beyond its good built-in feature set, there are numerous extensions available for it, as well as many many hidden options.

What follows below is a personal and biased (!) list of items that I have found useful, in order to give Thunderbird some functionality that it was initially lacking.

Thunderbird's extensions can be found at the web site http://addons.mozilla.com/thunderbird .

Extension name Why I like it
Image Zoom By default, large images are shown at 100%, meaning you can see only a small corner of them. With a right click followed by a left-click, this extension allows one to have the image fit in the current window and then zoom in and out from there.
Thread Key A nice keyboard shortcut to toggle Thunderbird's message list threading. (Threading groups messages together by subject or messageID.)
Mail Redirect Gives one back the "bounce" or "redirect" mail feature (Message menu and keyboard shortcut). If person A sends you a message, you can redirect it to person B so that it looks like it came directly from person A (no "fwd" in Subject or indenting (or even any editing) of message body).
Display Mail User Agent Extension Shows cute small icon indicating what email program the sender uses. (Useful for debugging as a sysadmin, just informative otherwise)
View Headers Toggle Button Provides toolbar button to show "full headers" (useful for debugging, once again) so that one does not have to keep going to View menu:Headers:All.
Growl New Message Notification (Mac only) Connects to "Growl" system for elegant transparent-then-fadeaway notices of new mail.
Attachment Sizes This extension lets you know how large each attachment is (as opposed the entire message size).
Quote Colors A subtle but nice enhancement to the idea of nested quoted messages having different colored bars on the left.

Extension name	Why I like it
Image Zoom	By default, large images are shown at 100%, meaning you can see only a small corner of them. With a right click followed by a left-click, this extension allows one to have the image fit in the current window and then zoom in and out from there.
Thread Key	A nice keyboard shortcut to toggle Thunderbird's message list threading. (Threading groups messages together by subject or messageID.)
Mail Redirect	Gives one back the "bounce" or "redirect" mail feature (Message menu and keyboard shortcut). If person A sends you a message, you can redirect it to person B so that it looks like it came directly from person A (no "fwd" in Subject or indenting (or even any editing) of message body).
Display Mail User Agent Extension	Shows cute small icon indicating what email program the sender uses. (Useful for debugging as a sysadmin, just informative otherwise)
View Headers Toggle Button	Provides toolbar button to show "full headers" (useful for debugging, once again) so that one does not have to keep going to View menu:Headers:All.
Growl New Message Notification (Mac only)	Connects to "Growl" system for elegant transparent-then-fadeaway notices of new mail.
Attachment Sizes	This extension lets you know how large each attachment is (as opposed the entire message size).
Quote Colors	A subtle but nice enhancement to the idea of nested quoted messages having different colored bars on the left.

There are a very large number of extensions available (and even more for its cousin, the Firefox web browser). By all means explore the "addons" website to see if there are extensions that intrigue or interest you. My list is just a starting point of ones that I like.

How to install Thunderbird Extensions

Download from the http://addons.mozilla.com/thunderbird page (or from the links above if you wish to try these).
Note: You may have to right-click (control-click on a Mac) to save the extension, especially if you are a Firefox user.
(Otherwise it may try to install it as a Firefox extension instead.)
Select the Tools Menu:Extensions item and a new window should appear.
Click the Install button
Navigate your local filesystem to locate the extension you wish to install.
The "Install Now" will be greyed out for a few seconds (with a countdown timer showing) as a sanity check that you really want to install the given item. Go ahead and click "Install Now".
Install other extensions or close this window.
Quit and Restart Thunderbird to make the new extension functional.

Changing hidden preferences: an example

I was not happy with how Thunderbird was setting up my messages when I did a Reply, having been used to the UNIX standard of "On such-and-such a date and time, so-and-so wrote:". It turns out that Thunderbird has a built-in way to fix this:

Open the Preferences panel (Thunderbird menu:Preferences on Macs; Edit menu:Preferences on Linux and Windows)
Click on "Advanced" tab.
Click on "Config Editor..." button.
Type "reply_header_type" in Filter (search) field box.
Double-click on the line mailnews.reply_header_type.
A new window (a sheet on OS X) should appear: Type "2" as the new value and click "OK".
(This line should now be boldface, showing that you changed a default value.)
Close this window and the Preferences window.

(By the way, I had to Google to find the name of what to change and its value; I did not just "browse" the long list in the config editor.)

Final note

This page was written just as Thunderbird 2.0 was coming out, but so far has only been tested for the 1.5.x version.

David Friedlander
20 April 2007

National Aeronautics and Space Administration

Goddard Space Flight Center

A necessarily personal list of preferred Thunderbird extensions

How to install Thunderbird Extensions

Changing hidden preferences: an example

Final note