 <p>Thunderbird AddOns are extensions for the Mozilla Thunderbird email client. They are written mostly in XUL (a flavor of XML) and Javascript.</p> <hr> <h3>Useful links</h3> <ul> <li><a href="https://addons.mozilla.org/en/thunderbird/" rel="nofollow">Official website</a></li> </ul> <hr> <h3>Related tags</h3> <ul> <li><a href="/questions/tagged/thunderbird" class="post-tag" title="show questions tagged &#39;thunderbird&#39;" rel="tag">thunderbird</a></li> </ul>