title: SmtpClient and app.config system.net configuration
body: <p>I'm having an issue with a .NET 3.5 library I'm developing to send emails.
  I put the <code>system.net</code> configuration into <code>app.config</code>:</p>
  
  <pre><code>&lt;system.net&gt;
    &lt;mailSettings&gt;
      &lt;smtp from="mail@domain.com"&gt;
        &lt;network host="myserver.com" port="25" defaultCredentials="true" /&gt;
      &lt;/smtp&gt;
    &lt;/mailSettings&gt;
  &lt;/system.net&gt;
  </code></pre>
  
  <p>And I instantiate the SmtpClient without params:</p>
  
  <pre><code>SmtpClient client = new SmtpClient();
  </code></pre>
  
  <p>But the configuration is not read (I'm trying to test the library with NUnit) and I get a <code>System.InvalidOperationException</code>, because the configuration is not read and thus the host is null.</p>
  
  <p>Shouldn't the configuration be read automatically?</p>