Message Composition

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Auto Resize Image Requires Restart

Resizer for inline and attachment images (JPEG, PNG, BMP and GIF image formats).
All platforms are supported (Windows, Linux and Macintosh).

Rated 4 out of 5 stars (33)
5,136 weekly downloads

Mail Merge Requires Restart Featured

Mass Mail and Personal Mail

Rated 5 out of 5 stars (162)
2,236 weekly downloads

Send Later Requires Restart

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

Rated 5 out of 5 stars (138)
2,002 weekly downloads

Signature Switch Requires Restart

Switch the signature on/off or choose a new one from your predefined set.

Rated 4 out of 5 stars (198)
802 weekly downloads

MEGAbird Requires Restart

Add MEGA support to Thunderbird's Filelink feature.

Rated 4 out of 5 stars (18)
727 weekly downloads

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 (119)
574 weekly downloads

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)
495 weekly downloads

Emoji Requires Restart

Add emojis to your e-mails.

Rated 5 out of 5 stars (16)
488 weekly downloads

Check and Send Requires Restart

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

Rated 4 out of 5 stars (31)
455 weekly downloads

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 (53)
414 weekly downloads

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 (40)
306 weekly downloads

Send Later Button Requires Restart

A simple button to invoke the (already existing) send later functions.

Rated 4 out of 5 stars (3)
259 weekly downloads

Flex Confirm Mail Requires Restart

Confirm mail address and attachments based on flexible rules.

Rated 3 out of 5 stars (5)
243 weekly downloads

Nextcloud for Filelink Requires Restart

"Nextcloud for Filelink" is an Open Source Thunderbird extension which makes it easy to send large attachments with Thunderbird by uploading them first to a Nextcloud server and by then inserting the link into the body of your email.

Rated 3 out of 5 stars (33)
231 weekly downloads

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 (9)
197 weekly downloads

Markdown Here Requires Restart

Write your email in Markdown, then make it pretty.

Rated 5 out of 5 stars (36)
184 weekly downloads

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).

Rated 5 out of 5 stars (9)
183 weekly downloads

Emoji Menu Requires Restart

Adds the ability to easily insert emojis into your composed messages in Thunderbird.

Rated 4 out of 5 stars (9)
179 weekly downloads

Shrunked Image Resizer Requires Restart

Make your photos smaller, so they don't take forever to email or send to websites.

This extension is not being converted to a WebExtension.

Rated 3 out of 5 stars (38)
170 weekly downloads

Grammar Checker Requires Restart

Checks grammar using LanguageTool.

Rated 3 out of 5 stars (8)
169 weekly downloads