Add-ons, extensions, and themes Enhance product functionality with add-ons, extensions, and themes. NgesiNgisi Filelink for Large Attachments Permission request messages for Thunderbird extensions Open Search Thunderbird add-ons - frequently asked questions Installing an Add-on in Thunderbird Unified Toolbar Install themes to change the look of Thunderbird How to Customize Toolbars Certificates How to Install and Use another Language in the Dictionary on Thunderbird Add-Ons FAQ Add Search Engine to Open Search How can I digitally sign and encrypt emails? How to Customize the New Mail Sound Installing and Using another Language in the Dictionary Unable to install add-ons (extensions or themes) in Thunderbird Unable to uninstall add-ons (extensions or themes) userChrome.css and .js and userContent are unsupported