install.rdf

<?xml version="1.0" encoding="UTF-8"?>
<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:em="http://www.mozilla.org/2004/em-rdf#">
    <Description about="urn:mozilla:install-manifest">
        <em:type>2</em:type> <!-- 2 : Extension -->
        <em:id>thunderbird.highlightnumber@felixmoeller.de</em:id>
        <em:version>0.0.1</em:version>
        <em:name>HighlightNumber</em:name>
        <em:creator>Felix Möller</em:creator>
        <em:targetApplication>
            <Description>
                <!-- Thunderbird -->
                <em:id>{3550f703-e582-4d05-9a08-453d09bdfdc6}</em:id>
                <em:minVersion>6.0</em:minVersion>
                <em:maxVersion>11.0a1</em:maxVersion>
            </Description>
        </em:targetApplication>
        <em:optionsURL>chrome://highlightnumber/content/options.xul</em:optionsURL>
        <em:aboutURL>chrome://highlightnumber/content/about.xul</em:aboutURL>
    </Description>
</RDF>