When a message cannot be forwarded the message should be released.
However, when the forwarding treatment is "unavailable" that message must be REJECTED (as per the description of the "unavailable" treatment).
When the router tries to determine if the outcome should be RELEASED or REJECTED it does not check for a matching router.config.address configuration entity. This entity contains a treatment for the given address. If an address configuration matches the address the treatment should come from the address configuration - not the router default configuration.
Configure a router with defaultTreatment set to unavailable.
Configure an address prefix that uses the "closest" treatment.
Attach a sender to the router using an anonymous link.
Send a message to an address that will match the configured address prefix while there are no subscribers.
Expect: the message be RELEASED by the router
Actual: the message is REJECTED by the router