Reply to Multiple Messages Requires Restart
Add menu commands for replying to multiple messages at the same time.
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
EnForward Requires Restart
Save your email into Evernote by forwarding it to Evernote email address.
Before you use it, you need to specify your Evernote email address (see the screenshot).
This function can be invoked by "Forward to Evernote" in the context menu.
SMTP Switch Reborn Requires Restart
Resubmit Requires Restart
(Re)submit multiple messages to a predefined recipient(s)
Uploads your large attachments to your DropBox instead of sending them by email
BorderColors D Requires Restart
Shows a colorful border around the "New Message" window, so you can tell different identities apart.
Builds on the original BorderColors and the "GT" version, adding different border styles.
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.
Make your photos smaller, so they don't take forever to email.
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).
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.
MEGAbird Requires Restart
Add MEGA support to Thunderbird's Filelink feature.
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).
Emoji Requires Restart
Add emojis to your e-mails.
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!
Grammar Checker Requires Restart
Checks grammar using LanguageTool.
Highlighter Requires Restart
Quickly highlight some text in Thunderbird message composing windows.
Reply As Original Recipient Requires Restart
Reply with the From: field set to the To: field from the original email.
One-by-One Forward Requires Restart
Highlight multiple emails, right-click, then select "One-by-One Forward". This extension will allow you to forward the selected emails, one-by-one, to the recipients you specify using your choice of attachment handling.
Don't Send Linked Files Requires Restart
Prevents sending of linked files if they are file: URLs.