title: Does Message Sampling Processor in WSO2 ESB support reliable messaging
body: <p>In <code>WSO2ESB</code> the message sampling processor de-queues the messages from the queue and forward it to a sequence where we can do transformation to the request and send to the back - end. And 
  <code>The main purpose of using MSMP is for archiving guaranteed delivery, or in other words, to archive reliable messaging.</code> <a href="http://wso2.com/library/articles/2014/01/guaranteed-delivery-with-Message-Store-Message-Processor%20/" rel="nofollow">[Source]</a></p>
  
  <p>But when we use <code>Message Sampling Processor</code> it just forward the message to sequence and the processor doesn't know whether the message successfully delivered to the back end (using <code>send</code> | <code>call</code> mediator) or  the processor knows this and restore the message in the queue?
  I tried this scenario using JMS-Message Store (<code>WSO2MB</code>) and what I found is, message get lost when the back end service is down.</p>