The problem is you don't really know if its already been sent or not. Then if the broker's gone down you need to recreate your connection, sessions, producers, consumers etc.
Its much easier to just use a JMS provider which supports auto-reconnection for you which totally hides and fixes all these problems
http://activemq.apache.org/how-can-i-support-auto-reconnection.html
James
http://logicblaze.com/
Open Source SOA