Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
Organize your schedule and life's important events in a calendar that's fully integrated with your Thunderbird email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.
United States English Spellchecker for Firefox, Thunderbird and SeaMonkey by Kevin Atkinson and Geoff Kuenning.
To enable, right-click in a multi-line text box, select "Languages", then "English (United States)".
Four French spelling dictionaries: “Moderne”, “Classique”, “Réforme 1990”, “Classique & Réforme 1990”
Allows bidirectional access to Google Calendar
OpenPGP message encryption and authentication for Thunderbird and SeaMonkey.
Displays icon for user agent of received mails.
Add arrow buttons for rotating among folder views, and switch to "All Folders" view when hovering over the folder pane during drag & drop.
Adds a summary of mail accounts and folders to replace the account central pane and the empty folder preview
This add-on provides a follow-up email feature for Thunderbird.