I don't know what you mean by the first attempt to deliver a message is made sychronously, and what makes you think that is the case.
Also I'm not sure what documentation you're referring to.
Apologies, I'm afraid I incorrectly interpreted the results of one of our failing test cases based on the following document, in particular the slide on Asynchronous Channel:
I know the document is old but it was one of the few descriptive documents we could find on JBoss Messaging. Out of interest, what was this slide referring to by "synchronous delivery"?
One other question, does JBM allow for deferred delivery, i.e. is there a similar message / destination level property to the JBoss MQ property JMS_JBOSS_SCHEDULED_DELIVERY? This no longer seems to be supported.