Up & Coming Extensions
Markdown document viewer.
Allows to visualize formatted markdown documents in browser.
Shows an indicator so you can tell if an email was addressed only to you (»), a group (›), or a mailing list.
An easier management of the user interface language
Adds a "File" menu option to open multiple locations at a time.
Displays icon for user agent of received mails.
Lets you load pages in IE with a single right-click, or mark certain sites to *always* load in IE.
ConfigDate allows to configure the "Date" column in message threadpane. When displaying the message header, it is possible to display the (default) formated date or the senders local sent time (Date-String).
Stop Tube HTML5 No Restart
Stops autoplay of YouTube HTML5 videos (WebM). It is Flash-Block equivalent for HTML5 videos.
Speed Start No Restart
Speed Dial & Start Page with flexible layout for fast access to sites via visual bookmarks
This add-on allows you run your message filters automatically on outgoing messages after sending. In other words, it's a outgoing filter for thunderbird and seamonkey.
AlexaTopSites No Restart
This add-on provides quick access to Alexa's Top Sites.
SmartTemplate4 offers an easy way to automatically create customized replies by auto-inserting various mail headers. Templates can be created for every account as well as for the default (all email accounts). Also supports the Stationery Add-on.
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).
Allows to place a copy of sent messages (aka FCC) into the currently active folder or any other folder you choose, when you create the message. Usually the copies are placed into the 'Sent' folder. For replies, you may also move the original message.
Finnish open source Voikko-spellchecker for Mozilla and needed libraries.
Check multiple checkboxes by drawing a rectangle around them. FF6 version.
I've made this version since i did need it for use with RTM,
LookOut is a plugin which allows to interface with Microsoft's mail tools by decoding metadata and attachments encapsulated/embedded in a TNEF encoded attachment (aka winmail.dat).
This version is a fix for Seamonkey 2.*.
True "Send Later" functionality to schedule the time for sending an email.
StartupMaster No Restart
Asks for the master password at startup (fixes multiple password prompt)