Add-ons, extensions, and themes

Filelink for Large Attachments

Messages with large attachments are often rejected by mail servers. Thunderbird can use web-based storage services to send large file attachments.

Permission request messages for Thunderbird extensions

More information about each permission request you may encounter when installing an extension into Thunderbird.

Thunderbird add-ons - frequently asked questions

Add-ons are extensions and other additions that add new functionality to Thunderbird or change its appearance.

Installing an Add-on in Thunderbird

Add-ons add functionality to Thunderbird or change its appearance. Learn how to install add-ons to Thunderbird.

How to Install and Use another Language in the Dictionary on Thunderbird

How to install and use additional language dictionaries on Thunderbird.

How to Customize Toolbars

This article explains how to customize the position and contents of Thunderbird toolbars.

Install themes to change the look of Thunderbird

A theme is a type of add-on which changes the visual appearance of Thunderbird. Learn how to find, install, and manage themes within Thunderbird.

userChrome.css and .js and userContent are unsupported

userChrome.css, userChrome.js, userContent.css and userContent.js are unsupported because they can break at any time and are difficult to troubleshoot.

Certificates

Add-Ons FAQ

Open Search

Instantly take part of a message and search for it in Bing, Yahoo, Twitter or other websites.

Add Search Engine to Open Search

Open Search enables Thunderbird users to search various websites from within Thunderbird. This article describes how to add additional websites to the Open Search interface.

How can I digitally sign and encrypt emails?

How to Customize the New Mail Sound

Learn how to customize the sound that plays when a new email message is received.

Installing and Using another Language in the Dictionary

Unable to install add-ons (extensions or themes) in Thunderbird

This article describes various reasons that would cause an add-on not to be able to be installed and what you can do to fix the issue.

Unable to uninstall add-ons (extensions or themes)

This article describes how to uninstall an extension or theme that can't be removed normally.

Unified Toolbar

Intro to the Unified Toolbar and how to customize the buttons for the different toolbars for: Mail, Address Book, Calendar, Tasks, Chat and Settings "Spaces."