Add-ons, extensions, and themes Enhance product functionality with add-ons, extensions, and themes. In English Filelink for Large Attachments Thunderbird add-ons - frequently asked questions Permission request messages for Thunderbird extensions Install themes to change the look of Thunderbird Installing an Add-on in Thunderbird How to Customize Toolbars How to Install and Use another Language in the Dictionary on Thunderbird Certificates Add-Ons FAQ How can I digitally sign and encrypt emails? 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)