code: private void sendFailedUpdateEmail(final Executor executor,
        final ExecutorManagerException exception, final MailCreator mailCreator,
        final ImmutableList<ExecutableFlow> flows) {
      final EmailMessage message = this.messageCreator.createMessage();
      final boolean mailCreated = mailCreator
          .createFailedUpdateMessage(flows, executor, exception, message,
              this.azkabanName, this.scheme, this.clientHostname, this.clientPortNumber);
      final List<Integer> executionIds = Lists.transform(flows, ExecutableFlow::getExecutionId);
      sendEmail(message, mailCreated, "failed update email message for executions " + executionIds);
    }
docs: Sends a single email about failed updates.