Top Useful Thunderbird Add-ons
Mozilla
Thunderbird is the safe, fast email client that's easy to use. It
has lots of great features including quick message search,
customizable views, support for IMAP/POP, RSS support and more.
Here are the top useful add-ons for it.
Contacts Sidebar - displays the address books in
Thunderbird sidebar. This lets you easily access all your contacts
from the main window, quickly edit contact details, drop files on
top of a contact to send it as an attachment and more?

Signature Switch- allows you to create multiple email
signatures (Private, Business, etc.) Sending emails to different
people mean to use different signatures. Try save signatures and
select them when you need . Also provides configurable signature
auto-switch option based on the email recipients.

Auto Zip Attachments- adds an AutoZip button to
Thunderbird which adds all attachments to an compressed archive,
removes the files from the list of attachments and adds the
compressed file instead to it. The AutoZip icon will be visible in
every compose mail window in Thunderbird. You may override the
default behavior of the extension and customize it to suit your
needs.
Nostalgy
- adds keyboard shortcuts to change folder, move/copy messages,
add attachment, scroll the message while keeping the focus on the
thread pane and lots more. Also includes a system of rules to
suggest a target folder for saving messages; re-creates Eudora's
Alt-Click; facilitates navigation in the 3-pane window; makes it
easy to change between To/Bcc/Cc fields in the composer; facilitates
tag-oriented operations.

GMailUI - is an extension to Thunderbird which
add concepts inspired by GMail to Thunderbird, like archiving mail
and powerful message searching across all folders. a folder to be
your sole "archive" folder, or choose to have an archive folder in
each of your multiple accounts.

Quicktext - is an extension for Thunderbird that lets you
create templates that can be easily inserted into your own emails.
Quicktext is the perfect tool to help you quickly answer routine,
repetitive emails. The program can insert different signatures into
your emails depending on whom you are sending the email to.

Remove Duplicate Messages - detects and deletes
duplicate messages from the selected folders .

Attachment Extractor - integrates one-click attachment
extract option from selected messages. Once attachments have been
extracted it can delete, detach or mark messages as "Read".

Send Later - lets you schedule the delivery of emails composed in Thunderbird. It can be a contract cancellation notice, a ?Happy Birthday? or a friendly ?Don?t Forget? note.

Lighting - The extremely popular calendar for
Thunderbird, modeled after Mozilla?s stand-alone Sunbird. This is
the only extension truly needed to get the full feel of Outlook.
Lightning Multiweek adds a multi-week view option within
Lightning
Text size adds text size (increase/decrease) buttons to
the main toolbar.

QuickFolders - allows you to bookmark easily mail
folders in Thunderbird. When you drag an e-mail folder to it, you
get a shortcut to that mail folder. You can also drag messages to
this shortcut to move/copy them to the folder. This is handy when
you have a large tree of folders for clients or projects, but use
only a few of them at the same time.

Mail Redirect - allows you to export messages out of
Thunderbird to another email address without forwarding. It
preserves all message headers and ?bounces? them to a provided email
address. (Thunderbird: 0.7 ? 2.0.0.*)

Buttons - Adds new buttons (such as ?Forward!?,
?Reply!?, and ?Reply All ")to the Thunderbird Toolbar to make
navigation easier.

E-mail notification Randomizer - Every time when an
email is received, the configured email notification sound is
updated from the set of wav files in the configured folder. This
extension also adds additional options in the Sound Notification
preferences pane to help the user control the modified behavior.

Dictionary Search - provides a fast way to
translate any word within an email message. Simply select the word
you want to lookup, access right-click menu and select ?Dictionary
Search for ??. A new tab or browser window will open with the
meaning of the word you selected.

Image Zoom- if you have an image that was too large to fit
on your screen or too small to see the finer detail in your browser
or email, then image zoom gives you complete control of the
size of most images displayed.

Allow HTML Temp - allows to have HTML temp
enabled/allowed in the selected message by only one click.

Mouse Gestures - Allows you to execute common commands
(as page forward/backward, close tab, new tab) by mouse gestures
drawn over the current webpage, without reaching for the toolbar or
the keyboard...

XNote - provides an option to add sticky-like
notes/memos to desired messages

TimeStamp - inserts the current date/time into a
message or an input field in the browser.

Skype Toolbar - initiates calls, chat sessions,
transfer files to your Skype contacts within Thunderbird, view
sender?s account status (online, offline), etc.

View
Headers -adds a toolbar button that allows the easy
toggling of viewing all message headers.

Spamato - is a spam filter extension for the Mozilla
Thunderbird email client. It contains several different spam filters
bundled as one powerful component which (as we believe) is much more
effective than the built-in Thunderbird solution.

Smile Insert - adds smile faces to your messages.

Quote Collapse - allows you to collapse automatically all quotes in your e-mails to make them more readable.
Change - allows currency converter. It convert between 36 currencies directly from your toolbar.
QuickMove - allows you to access common folders quickly
Growl Notifications - displays notification for a new mail as soon as it is received.
Minimize to try - Minimizes the Windows versions of Thunderbird to the system tray. You can only minimize it to the taskbar or close it completely



