Message Composition

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Send Later Requires Restart

True "Send Later" functionality to schedule the time for sending an email.

Rated 5 out of 5 stars (105)
70,182 users

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.

Rated 5 out of 5 stars (52)
18,862 users

Automatic Dictionary

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.

Rated 5 out of 5 stars (33)
3,817 users

Transliterator

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.

Rated 5 out of 5 stars (88)
4,475 users

Mail Merge Requires Restart Featured

Mass Mail and Personal Mail

Rated 5 out of 5 stars (150)
64,522 users

AVIM Requires Restart

Vietnamese-language input method editor (IME). Type diacritics directly into any Web page, Web app, or dialog box. Convenient, comprehensive, secure.
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Bộ gõ tiếng Việt cho phép đặt dấu trực tiếp vào bất kỳ trang Web, ứng dụng Web, hộp thoại.

Rated 5 out of 5 stars (39)
1,808 users

MEGAbird Requires Restart

Add MEGA support to Thunderbird's Filelink feature.

Rated 5 out of 5 stars (10)
2,072 users

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/

Rated 5 out of 5 stars (30)
5,517 users

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.

Rated 5 out of 5 stars (17)
2,237 users

SmilieInserter Plus Requires Restart

Insert smilies in messages.

Rated 5 out of 5 stars (21)
2,926 users

ThunderPEC Requires Restart

ThunderPEC semplifica la gestione della Posta Elettronica Certificata (PEC) e delle comunicazioni PCT e FatturaPA in Thunderbird.

Rated 5 out of 5 stars (11)
23,200 users

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).

Rated 5 out of 5 stars (8)
3,547 users

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.

Rated 5 out of 5 stars (5)
2,805 users

Send and Archive Requires Restart

Adds a button to send an email and archive the original message.

Rated 5 out of 5 stars (10)
298 users

ReplyWithHeader Requires Restart

Outlook style headers and few goodies for Thunderbird & Postbox.

Rated 5 out of 5 stars (11)
1,636 users

DL for Thunderbird Requires Restart

Allows to convert large attachments to links automatically without 3rd party providers.

Rated 5 out of 5 stars (4)
1,919 users

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.

Rated 5 out of 5 stars (4)
27 users

Stop Ignoring Reply:To Requires Restart

Default "Reply" functionality pays attention to "Reply-To" in original email

Rated 5 out of 5 stars (4)
102 users

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!

Rated 4 out of 5 stars (104)
36,298 users

Check and Send Requires Restart

Check the message contents and addresses before you send the message...

Rated 4 out of 5 stars (30)
14,133 users