Guaranteed delivery to dynamic recipient list

Question

I have an upcoming project to provide guaranteed delivery of notification messages over web-services to a dynamic recipient list. We're currently using Synapse for some other transformation, routing, and proxying requirements, and I'm keen to continue to use Synapse or WSO2 if they're a good fit for the task.

Synapse/WSO2 provide WS-ReliableMessaging for guaranteed delivery to a single recipient, and provide the RecipientList mediator. However, it's not obvious how to combine the two.

I need guaranteed delivery on a per-recipient basis.

Does WSO2 provide this?

One option might be to use the Message Store/Message Processor pattern. A clone of the message could be dumped onto the Message Store, one for each recipient, along with an embedded url of the intended recipient (possibly with a custom mediator). A Message Processor could send each message clone to their intended recipients. But an important question: does the Message Processor stop on the first failed send and continue to retry that one alone, blocking all the messages behind in the queue? My guess is that it would block on the first failed message until it is successful.