Thunderbird is not quite as downloaded as Firefox these days, but it is a good start to what hopefully will become a powerful email client.

In my daily use, I’ve tried many extensions and uninstalled most. However, here are 8 that I love:

• Lightning - Having a calendar right in your email client makes it easy to see your schedule and what you’ve got to get done. Plus it brings along the ability to accept Outlook meeting requests which is needed in a corporate environment.
• Provider - What’s better than a calendar? Well a calendar that synchronizes back and fourth with Google Calendar. And for free!
• QuickText - This little buddy saves chunks of text like bookmarks. You then choose the bookmark and it inserts the text to go along with it in your email. Works great for any repetitive items that you find yourself typing over and over again.
• Growl Notifications (Mac) - Get notified of new mail messages without bring Thunderbird to the front. Windows has its own notifications, but Mac users were left out until now.
• GMailUI - This handy extension takes searching your inbox to the next level by allowing expressions to work with searches. Take the 5 minutes to learn it and you’ll love it.
• Nostalgy - Another brilliant extension that makes filing emails, or navigating to other folders, a snap via a shortcut and a quick search. Huge time saver.
• Mail Redirect - Just because the email came to you, doesn’t mean you are the best recipient. Forward emails as though they were specifically sent to someone else. This is handy for me as I build a lot of forms, and sometimes forget to update the ‘to’ email when they go live.
• AttachmentReminder - This handy extension reads the email you’re composing and reminds you if you said you were going to send an attachment, but didn’t attach anything. Very handy!

Yes, there are lots of other extensions out there, but not many that I’ve come across that really bring additional functionally and usefulness to Thunderbird.

Do you have others that you find quite helpful? Post them below in the comments as I’d love to check them out!