If you’re not yet acquainted with it, Thunderbird is Mozilla’s desktop email client. I’ve been using it for a couple of years now as an alternative to Outlook because it’s more lightweight and seems to handle large volumes of mail better.
Mozilla’s philosophy is to build products that are lightweight on initial installation, which you then have the choice to extend later by downloading additional plug-ins which they call extensions.
These are the 6 extensions that I’ve found most useful over the years. All of the extensions mentioned run in current version of Thunderbird 2.0.0.9 (20071031)
Lightning
Lightning provides calendering and task management for Thunderbird. You can multiple calendars to help separate work and private life and subscribe to or import external calendars.
It has all the Day, Week and Month Views that you’d expect of a decent calendar programme and if you set dates for your tasks, they will also appear in the calendar.
Thunderbird In Month View

Thunderbird In Week View

Download Lightning here addons.mozilla.org/en-US/thunderbird/addon/2313
Provider For Google Calendar
The Google provider for Lightning enables it to not only subscribe to your Google Calenders, but to also write back information to Google. So if you an an event in Thunderbird, it’ll synchronise back to your Google calendar and vice versa.
At the moment the Google Provider for Lightning is only able to sync calendar events, not tasks. All of your tasks will have to be stored in a local calendar.
Download: addons.mozilla.org/en-US/thunderbird/addon/4631
Duplicate Remover
As people change their email address or move around from company to company, you inevitably end up with some old or duplicate contact records in your address book.
The Duplicate Remover extension runs a check on all of the contacts in your address book and when it finds potential duplicates it presents them to you side by side with the option to delete one of them.

You can choose to ignore the suggested duplicates, edit the information in both or delete the suggested record. Unlike Apple’s address book, there’s no merge function, but I’m sure that’s top of their list for extending functionality the functionality.
It’s fairly quick, but of course that’ll depend on how many contacts you have, but you shouldn’t need to run it that often.
Download: addons.mozilla.org/en-US/thunderbird/addon/2505
Address Book Side Bar
One thing that is missing from the default installation of Thunderbird is a pane which enables you to quickly glance through a list of all your contacts and choose which ones to send the email to.

The Address Book Sidebar fulfils that role and can be called up whether you are creating a new message or not.
Download: addons.mozilla.org/en-US/thunderbird/addon/70
Signature Switcher
If you use Thunderbird for work and private email or if you have to respond in different roles at work Siganture Switcher is a very handy tool that let’s you create a number of different signatures for signing off your emails and then choose which one you use at then end of each message.

But it goes beyond simply being able to manually choose which signature to append to a message. It can also be configured to automatically choose which signature to use based on who you are replying to or the recipients of a mailing list you are using to send out the email.

Download: addons.mozilla.org/en-US/thunderbird/addon/611
MagicSLR
If you use Thunderbird to collect mail from more than one account MagicSLR is a handy little toll that enables you to hit one button and it send and receive all of your mail for all of your accounts.
Download: addons.mozilla.org/en-US/thunderbird/addon/902
Toolbar Buttons
As you get more familiar with Thunderbird you’ll probably want to change the tool bar options to include the functions that you use most often. There are loads of functions available, but not all have a button, so you’ll need the Toolbar Buttons extenison.
Filed under: Free Fridays, Free Software, Information Management, Reviews, Thunderbird , contacts sidebar, duplicate remover, extensions, lightning, mozilla, task management, Thunderbird