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.
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.
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
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.
Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
CategoryManager 2 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).
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.
SmilieInserter Plus Requires Restart
Insert smilies in messages.
Markdown Here Requires Restart
Write your email in Markdown, then make it pretty.
Clippings Requires Restart
Save frequently-entered text for pasting later.
Emoji Requires Restart
Add emojis to your e-mails.
ThunderPEC Requires Restart
ThunderPEC semplifica la gestione della Posta Elettronica Certificata (PEC) e delle comunicazioni PCT e FatturaPA in Thunderbird.
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.
replyTo Requires Restart
Adds a menuitem to the Mail context Menu to Reply to a different Mailadress
CryptoData Requires Restart
Easily and quickly to encrypt / decrypt:
Private messages via e-mail, blogs, social networks, forums, websites, images, etc
Support: Firefox, Thunderbird and SeaMonkey
ReplyWithHeader Requires Restart
Outlook style headers and few goodies for Thunderbird & Postbox.
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.
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!