PMDF System Manager's Guide

If a host/domain specification fails to match any rewrite rule and no default rule is present, PMDF simply uses the specification "as-is"; i.e., 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. This relaxed interpretation of rewrite rule failures allows isolated PMDF sites that only communicate with a small number of systems to get by without any rewrite rules whatsoever.