Most Popular Extensions
Signature Switch Requires Restart
Switch the signature on/off or choose a new one from your predefined set...
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
Remove Duplicate Messages (Alternate) Requires Restart
Search and remove messages which are the same as other messages in your mail folders (referred to as duplicates or dupes).
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
Saved Password Editor Requires Restart
Adds the ability to create and edit entries in the password manager.
DOM Inspector Requires Restart
DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.
Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
LookOut (fix version) Requires Restart
LookOut is a plugin which allows Thunderbird to interface with Microsoft's mail tools by decoding metadata and attachments encapsulated/embedded in a TNEF encoded attachment (aka winmail.dat).
Support: Thunderbird and SeaMonkey
Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.
Google Calendar Tab Requires Restart
Adds the Google Calendar web interface as a new tab directly into Thunderbird. Creating and viewing events works just as it would in a browser like Firefox
ReminderFox Requires Restart
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.
Remove Duplicate Messages Requires Restart
If you have duplicate messages (e.g. from merging folders or downloading messages several times) you can use this tool to find and remove them from the selected folder and its subfolder by rightclicking on a folder and choosing "Remove duplicates..."
Mail Redirect Requires Restart Featured
Allow to redirect (a.k.a. "remail") mail messages to other recipients.
Google Docs Viewer (PDF, DOCX, PPTX, XLSX, etc...) Requires Restart
View publicly-accessible PDF, DOCX, PPTX, XLSX, among other files online with Google Docs by only 2 clicks. Click as usual for your default viewer. Support bookmarked URLs. Security and your explicit viewing intention are always honored.
Display Quota Requires Restart
This extension will display the current status of your IMAP quota in thunderbird's statusbar and will warn you when you reach a configurable limit...
Addressbooks Synchronizer Requires Restart
Synchronizes selected addressbooks with other instances of thunderbird
using ftp/webdav/imap servers
PrintingTools Requires Restart
Adds some options to print messages and addressbooks
Stationery Requires Restart
Extension to mimic Outlook Express Stationery.
Allow you to use HTML files as templates for mail. Also allow custom template in replies or forwarded mail!
AttachmentExtractor Requires Restart
Extracts all attachments from selected messages and then can delete, detach or mark-read.
FireTray Requires Restart
A system tray extension for Linux and Windows, allowing to set up custom icon, hiding to tray instead of closing, display the number of unread messages in mailing applications, and other features ...