 <p>When working with HTTP content (which is the case of Safari and Mail app), you must not forget to handle its content type. The <a href="https://developer.apple.com/library/mac/documentation/Miscellaneous/Reference/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html" rel="nofollow">Uniform Type Identifier</a> (UTI) for handle content type is <code>public.mime-type</code> and let's say that the content type header of a server response is set to <em>application/gpx</em>, so in your <em>plist</em> you must add to the <code>UTTypeTagSpecification</code> section:</p> <pre><code>&lt;dict&gt; &lt;key&gt;public.filename-extension&lt;/key&gt; &lt;array&gt; &lt;string&gt;GPX&lt;/string&gt; &lt;string&gt;gpx&lt;/string&gt; &lt;/array&gt; &lt;key&gt;public.mime-type&lt;/key&gt; &lt;string&gt;application/gpx&lt;/string&gt; &lt;/dict&gt; </code></pre> <p><strong>Note</strong>: I've seen <em>application/gpx</em> and <em>application/gpx+xml</em> as content type for GPX data around web and I don't know if there's a standard mime type so it's better to use both.</p>