title: nlog logger and filters
body: <p>I want to apply a filter to stop certain errors coming through via email but still have them logged to a file</p>
  
  <p>f is a file target and m is the mail target, both working fine until i apply this filter:</p>
  
  <pre><code>&lt;rules&gt;
    &lt;logger name="*" minlevel="Error" writeTo="f" /&gt; 
    &lt;logger name="*" minlevel="Error" writeTo="m" &gt;
      &lt;filters&gt;
        &lt;when condition="contains(${message}, 'Some message exception text')" action="Ignore" /&gt;
      &lt;/filters&gt;
    &lt;/logger&gt;
  &lt;/rules&gt;
  </code></pre>
  
  <p>If an error is thrown that contains 'Some message exception text' I was expecting an entry to still appear in the file log but it doesn't. I don't receive an email, which is what I wanted, but nothing is logged to the file.</p>
  
  <p>Have I setup the filters incorrectly or is this the expected behaviour of nlog?</p>