Well, obvious you test for this sort of case.
But AFAIK, JBoss won't send duplicate messages.
Genman, the first part of your answer is correct.
"Suck it and see", or just read the spec.
The second part is not correct/misleading.
Though it is quite hard for a BMT MDB to signal a NACK/rollback,
short of crashing the server :-)
See the FAQ or the dozens of previous posts where this is discussed in detail.
You can tell there are previous posts discussing this, because it is an FAQ.
Moderated: Lazy user