Table of Contents.What is an add-on?Add-ons are extensions and other additions that add new functionality to Thunderbird or change its appearance. Thunderbird has an open, extensible design and program architecture. This enables people to create 'add-ons' to Thunderbird.Who creates add-ons?Add-ons are mostly created by Mozilla volunteers, not Mozilla staff members (although some staffers write add-ons in their spare time). In general, though, Mozilla is generally not directly involved in the development of add-ons. Also, while Mozilla hosts a site where developers can distribute their add-ons, and while Mozilla reviews the add-ons that are distributed through that site, Mozilla is not responsible for supporting add-ons. If you need help with an add-on, you should contact the add-on's author.Where do I get add-ons?Most Thunderbird add-ons are distributed via the (although authors can distribute their add-ons any way they choose). You can search and browse the add-ons site either using a web browser or from Thunderbird itself (select the menu button Add-ons or Tools Add-ons to browse add-ons).How do I install an add-on?There are two ways you may install add-ons: from within Thunderbird and from outside Thunderbird.Installing add-ons downloaded from outside Thunderbird (e.g.
So if you're sick of the pale blue colour that Thunderbird uses as a default, you can change it by installing a theme extension. To browse and install extensions, select the Add-Ons option from the Tools menu within Thunderbird. If you don't see the menu line, press and release the Alt key and it will appear.