Add-ons

Header Tools Improved by Dillinger

Allows to modify headers and source of messages

ShowFolderSize-T by Toshi

Shows folders size on disk.

This add-on is a fork of ShowFolderSIze.
https://freeshell.de//~kaosmos/index-en.html#foldersize

PrintingTools NG by Christopher Leidigh

PrintingTools NG enables many layout and formatting options for printing messages with header borders, sorting, attachment lists etc. PDF output can be auto named and Page options can ease printer settings.

It is your printing toolbox.

Monterail Dark 2 for TB>68 by conema

Monterail Dark, a Thunderbird theme inspired by the mockup of Monterail

Remove Duplicates by Dillinger

Removes duplicate messages

ImportExportTools NG by Christopher Leidigh

Adds tools to import/export messages and folders

EML, MBOX, HTML PDF , Plaintext Support and CSV support with indexes and file naming.

Disable DragAndDrop (New) by Takayama Fumihiko

Disable drag and drop on the folder tree in order to prevent unintended folder movement.

Limit non-BCC recipients by DaveRo

Check that number of non-BCC recipients does not exceed a parameter.

Search Button by C-E

Toolbar button to invoke message search dialog window.

white by hazelnut

DeepDark for Thunderbird by steva

Dark mode for Thunderbird UI

FileLink Provider for OwnCloud and NextCloud by Thomas Spellman

Uploads your large attachments to your OwnCloud or NextCloud server and instead inserts a public link into your email.

*cloud - FileLink for Nextcloud and ownCloud by Johannes Endres

Upload large attachments to your Cloud and send the link by email

Auto Address Cleaner by Toshi, John Bieling

Remove comment, display name from addresses before sending mail.

changeQuote by caligraf

It's an extension that changes the format of reply header.
You can choose between the standard Thunderbird reply header, a detailed reply header or a Customized reply header.
You can configure it in the Tools ->Add-on Preferences -> changeQuote.