Hmmm, I find it strange that JBossMQ has different behaviour since we are using the exact same JCA layer as JBoss MQ. Unless JBossMQ is doing something weird internally like sending messages from an XASession if they haven't been sent when it closes - which is certainly not mandated by the JMS spec. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3968712#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...