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.
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.
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
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. NOTE: This is the legacy XUL version, for Thunderbird, Postbox, Pale Moon, etc. *Not* for modern Firefox; for that use this: https://addons.mozilla.org/en-US/firefox/addon/markdown-here/
MEGAbird Requires Restart
Add MEGA support to Thunderbird's Filelink feature.
Stop Ignoring Reply:To Requires Restart
Default "Reply" functionality pays attention to "Reply-To" in original email
SmilieInserter Plus Requires Restart
Insert smilies in messages.
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.
ThunderPEC Requires Restart
ThunderPEC semplifica la gestione della Posta Elettronica Certificata (PEC) e delle comunicazioni PCT e FatturaPA in Thunderbird.
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).
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.
DL for Thunderbird Requires Restart
Allows to convert large attachments to links automatically without 3rd party providers.
PennyPost Requires Restart
This extension makes it very easy to generate and attach stamps to outgoing mail. It also automatically detects and verifies stamps on incoming emails. The MBound algorithm requires a 16MB fixed table to work, HashCash is more CPU intense.
Send and Archive Requires Restart
Adds a button to send an email and archive the original message.
Custom Address Sidebar Requires Restart
Allow you to help address sidebar more useful.
Emoji Requires Restart
Add emojis to your e-mails.
ReplyWithHeader Requires Restart
Outlook style headers and few goodies for Thunderbird & Postbox.