Implementions of this interface allow certain appenders to decide
when to perform an appender specific action.
For example the SMTPAppender sends
an email when the isTriggeringEvent(LoggingEvent) method returns
true and adds the event to an internal buffer when the
returned result is false.
For example the SMTPAppender sends an email when the isTriggeringEvent(LoggingEvent) method returns
trueand adds the event to an internal buffer when the returned result isfalse.