title: log4net smtpappender subject based on log level
body: <p>Is it possible to configure log4net to have two smtp appenders - one that sends emails only when log level is >= WARN and second that sends everything, but never two on the same time.</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;appender name="SmtpAppenderWarn" type="log4net.Appender.SmtpAppender"&gt;
    &lt;to value="to@domain.com" /&gt;
    &lt;from value="from@domain.com" /&gt;
    &lt;subject value="Import completed with warnings / errors" /&gt;
    &lt;smtpHost value="localhost" /&gt;
    &lt;bufferSize value="512" /&gt;
    &lt;lossy value="true" /&gt;
    &lt;evaluator type="log4net.Core.LevelEvaluator"&gt;
      &lt;threshold value="WARN"/&gt;
    &lt;/evaluator&gt;
    &lt;layout type="log4net.Layout.PatternLayout"&gt;
      &lt;conversionPattern value="%newline%date [%thread] %-5level %logger [%property{NDC}] - %message%newline%newline%newline" /&gt;
    &lt;/layout&gt;
  &lt;/appender&gt;
  &lt;appender name="SmtpAppenderSuccess" type="log4net.Appender.SmtpAppender"&gt;
    &lt;to value="to@domain.com" /&gt;
    &lt;from value="from@domain.com" /&gt;
    &lt;subject value="Import completed successfully" /&gt;
    &lt;smtpHost value="localhost" /&gt;
    &lt;bufferSize value="512" /&gt;      
    &lt;layout type="log4net.Layout.PatternLayout"&gt;
      &lt;conversionPattern value="%date %-5level %logger: %message%newline" /&gt;
    &lt;/layout&gt;
    &lt;filter type="log4net.Filter.LevelMatchFilter"&gt;
      &lt;levelToMatch value="INFO" /&gt;
    &lt;/filter&gt;      
  &lt;/appender&gt;
  </code></pre>
  
  <p>I my application I have:</p>
  
  <pre class="lang-cs prettyprint-override"><code>Log.Info("Importer is starting...");
  //my logic
  //if warn Log.Warn("Warning...");
  Log.Info("Import finished");
  </code></pre>
  
  <p>So I'm using INFO all the time. Now when I encounter WARN both messages are being sent. I wish of course that the one with success info was not sent.</p>