限制来自smtpappender的电子邮件(log4Net)

<log4net>
  <appender name="BufferingForwardingAppender" type="log4net.Appender.BufferingForwardingAppender">
   <bufferSize value="100" />
    <lossy value="true" />
   <evaluator type="log4net.Core.LevelEvaluator">
      <threshold value="ERROR" />
    </evaluator>
    <appender-ref ref="SmtpAppender" />
  </appender>

  <appender name="SmtpAppender" type="log4net.Appender.SmtpAppender">
    <to value="recipient@example.com" />
    <from value="sender@example.com" />
   <subject value="Error Report" />
    <smtpHost value="smtp.example.com" />
   <bufferSize value="100" />
    <lossy value="true" />
   <evaluator type="log4net.Core.LevelEvaluator">
      <threshold value="ERROR" />
    </evaluator>
   <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%newline%date [%thread] %-5level %logger - %message%newline%newline%exception" />
    </layout>
  </appender>
</log4net>