ThunderHTMLedit Requires Restart
Thunderbird HTML editor. This add-on adds a HTML tab to the composition window where you can see and edit the HTML source of the message.
Stop Ignoring Reply:To Requires Restart
Default "Reply" functionality pays attention to "Reply-To" in original email
Reply to Multiple Messages Requires Restart
Add menu commands for replying to multiple messages at the same time.
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
MEGAbird Requires Restart
Add MEGA support to Thunderbird's Filelink feature.
SmartTemplate4 Requires Restart
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.
CategoryManager Requires Restart
Category manager for Thunderbird contacts, also allows to send an email to all members of a category (categories can be used as contact groups).
Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
As-you-type phonetic conversion of text from one alphabet to another, as well as transliteration/detransliteration of selected text anywhere within documents. Supports multiple languages and custom transliteration schemes.
Remembers the language you use with a person or group of people, and switches the spellchecker language automatically for you next time. You do not have to do it manually any more. It remembers and switches it for you.
AVIM Requires Restart
Vietnamese-language input method editor (IME). Type diacritics directly into any Web page, Web app, or dialog box. Convenient, comprehensive, secure.
Bộ gõ tiếng Việt cho phép đặt dấu trực tiếp vào bất kỳ trang Web, ứng dụng Web, hộp thoại.
Markdown Here Requires Restart
Write your email in Markdown, then make it pretty.
Emoji Requires Restart
Add emojis to your e-mails.
Extra Format Buttons Requires Restart
Adds a font size (in pixels), strikethough, subscript and superscript buttons to Thunderbird's Compose Window.
Color Text Compose Buttons Requires Restart
Adds Text Color Buttons in Compose Toolbar and More: Pixel FontSize, Strikethough, Sub & Superscript, Lower & UpperCase. Also provide Tools: Insert iframe, Launch MathType, Maths & Greek Symbols, Load Template Variables and Duplicate Compose Window.
Send and Archive Requires Restart
Adds a button to send an email and archive the original message.
DL for Thunderbird Requires Restart
Allows to convert large attachments to links automatically without 3rd party providers.
SmilieInserter Plus Requires Restart
Insert smilies in messages.
Attach from Clipboard Requires Restart
Create file attachments directly from the system clipboard.
Warns if you send mail from or to a specified domain. If there are multiple accounts in your profile, you can isolate one so that you can't send mail to that domain from outside or vis versa without warning.