Signature Switch Requires Restart
Switch the signature on/off or choose a new one from your predefined set...
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
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!
ThunderPEC Requires Restart
ThunderPEC semplifica la gestione della Posta Elettronica Certificata (PEC) e delle comunicazioni PCT e FatturaPA in Thunderbird.
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.
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).
Flex Confirm Mail Requires Restart
Confirm mail address and attachments based on flexible rules.
Check and Send Requires Restart
Check the message contents and addresses before you send the message...
Highlighter Requires Restart
Quickly highlight some text in Thunderbird message composing windows.
Emoji Requires Restart
Add emojis to your e-mails.
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.
Emoji Menu Requires Restart
Adds the ability to easily insert emojis into your composed messages in Thunderbird.
Extra Format Buttons Requires Restart
Adds a font size (in pixels), strikethough, subscript and superscript buttons to Thunderbird's Compose Window.
Toggle Word Wrap Requires Restart
Toggle word wrapping and PRE element wrapping in the message composition and HTML display windows, respectively.
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/
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.
Send Later Button Requires Restart
A simple button to invoke the (already existing) send later functions.
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.
BorderColors GT Requires Restart
How many time you sent an email from your wrong email address?
This add-ons allows you assign a different color to the compose window border for each of your email addresses. So you can immediately view from what account are you writing.