Sun Java System Messaging Server 6.3 Administration Guide

11.5.5 Rewrite Rule Failure

If a host/domain specification fails to match any rewrite rule and no default rule is present, the MTA uses the specification “as-is”; for example, the original specification becomes both the new specification and the routing system. If the address has a nonsensical host/domain specification it will be detected when the routing system does not match any system name associated with any channel and the message will be bounced.