Attempting to configure an executor bus channel for join will result in a runtime error ... an executor bus only supports outbound semantics.

    /**
     * Called by the executor bus to process a message sent through the executor bus.  
     * <p>
     * The implementer may perform the send in the thread calling this method or 
     * pass the message off to a thread pool that it manages for greater parallelism. 
     * <p>
     * Users of an executor bus should be able to expect ordered processing of messages 
     * on a per channel basis, so implementations that are perform processing on multiple
     * threads are encourage to call {@link MessageView#getMessageChannel()} to determine 
     * the execution channel and process accordingly. 
     * 
     * @param view The view to send. 
     * @param acknowledger The acknowledger or <code>null</code> if no acknowledgement is required for processing this message. 
     * @param flags Flags provided by the executor bus as hints to the processor. 
     */
    public void process(MessageView view, Acknowledger acknowledger, int flags) throws Exception;

public class EmailGatewayProcessor implements LifecycleAwareExecutorBusProcessor {
 
    private final Tracer tracer = Tracer.create("email.sender", INFO);
    private volatile JavaMailSenderImpl mailer;

    /**
     * Called by executor bus prior to open. 
     */
    @Override
    public void onExecutorBusOpen(MessageBusBinding binding) throws Exception {
        // Get config properties:
        Properties config = binding.getDescriptor().getProviderConfig();
        mailer = new JavaMailSenderImpl();
        mailer.setHost(config.getProperty("smtp_host"));
        mailer.setPort(Short.valueOf(config.getProperty("smtp_port")));
        mailer.setUsername(config.getProperty("smtp_user"));
        mailer.setPassword(config.getProperty("smtp_password"));
        mailer.setProtocol(config.getProperty("smpt_protocol"));
        //etc...
        tracer.log("EmailSender opened", INFO);
    }
    /**
     * Called by executor bus binding on open. 
     */
    @Override
    public void onExecutorBusStart(MessageBusBinding binding) throws Exception {
        tracer.log("EmailSender started", INFO);
    }
    /**
     * Called by executor bus binding on close. 
     */
    @Override
    public void onExecutorBusClose(MessageBusBinding binding) throws Exception {
	    mailer = null;
        tracer.log("EmailSender closed", INFO);
    }
 
    /**
     * Executor bus callback. 
     * 
     * @param message The message to send. 
     * @param acknowledger The acknowledger for the message. 
     * @param flags Additional flags provided by the executor binding. 
     */
    @Override
    public final void process(MessageView message, Acknowledger acknowledger, int flags) {
        try { 
          final MimeMessage template = mailer.createMimeMessage();
          final MimeMessageHelper helper = new MimeMessageHelper(template, true);
          
		  helper.setSubject("ALERT: " + message.getClass().getSimpleName());
          helper.setText(message.serializeToJson(), false);
          // etc...
 
          // send
          mailer.send(template);

          //acknowledge completion:
          acknowledger.acknowledge();
        }
        catch (Exception e) {
          // Acknowledge with a failure (to close the bus): 
          acknowledger.acknowledge(e);
        }
    }
}
 

/**
 * 
 */
public class EmailGatewayProcessorFactory extends AbstractExecutorBusProcessorFactory {
    private static volatile EmailGatewayProcessor emailGatewayProcessor;

    /* (non-Javadoc)
     * @see com.neeve.sma.spi.executor.AbstractExecutorBusProcessorFactory#createExecutorBusProcessor(com.neeve.sma.MessageBusBinding)
     */
    @Override
    public ExecutorBusProcessor createExecutorBusProcessor(MessageBusBinding binding) {
        return emailGatewayProcessor;
    }
    /**
     * Registers the tibco send processor. 
     * 
     * @param tibcoSendProcessor The tibco send processor. 
     */
    public static void register(SolaceToRvBridge tibcoSendProcessor) {
        PumaExecutorBusProcessorProvider.tibcoSendProcessor = tibcoSendProcessor;
    }
}

@AppHAPolicy(value = HAPolicy.StateReplication)
public class EmailGatewayApp {
	private volatile AepMessageSender messageSender;
 
    @AppInjectionPoint
    public void setMessageSender(AepMessageSender messageSender) { 
       this.messageSender = messageSender;
    }
    
    @EventHandler
    public void onAlert(MyAppAlertMessage alert) {
      // Send a copy of the received alert out through the
      // email-alerts channel of the e-mail bus: 
      messageSender.send("email-alerts", alert.copy()); 
    }
}

<buses>
  <bus name="alert-bus">
    <provider>solace</provider>
    <address>localhost</address>
    <port>
    <channels>
      <channel name="app-alerts">
        <qos>Guaranteed</qos>
      </channel>
    </channels>
  </bus>
  <bus name="email-gatewaysender">
    <provider>executor</provider>
    <address>audit-logger</address>
    <properties>
      <processor_factory_classname>com.example.MyAuditLogWriterFactory<EmailGatewayProcessorFactory</processor_factory_classname>
      <from_address>admin@example.com</from_address>         
      <smtp_host>mail.example.com</smtp_host>          
      <smtp_port>25</smtp_port>            
      <smtp_password>admin</smtp_password>      
      <!--... and so on.-->   
    </properties>
    <channels>
      <channel name="executionemail-reportsalerts">
        <qos>Guaranteed</qos>
      </channel>
    </channels>
  </bus>
</buses>
 
<apps>
  <app name="EmailGatewayemail-gateway-app" mainClass="com.example.EmailGatewayEmailGatewayApp">
    <messaging>
      <buses>
        <bus name="filealert-outputbus">
          <detachedSend enabled="${TIBCO_DETACHED_SEND_ENABLED::truefalse"/>
          <channels>
            <channel name="app-alerts" join="true"/>
          </channels>
        </bus>
        <bus name="email-sender">
          <detachedSend enabled="true}">
            <queueDrainerCpuAffinityMask>${TIBCOEMAIL_DETACHEDSENDER_SENDCPU_CPUAFFMASKAFFMASK::0}</queueDrainerCpuAffinityMask>
          </detachedSend>
          <channels>
            <channel name="executionemail-reportsalerts" join="false"/>
          </channels>
        </bus>
      </buses>
    </messaging>
  </app>
</apps>