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When Send NPDI enabled is enabled On on an Origination Customer or a Termination Vendor Trunk Group , the Orchestrator adds a Number Portability Dip Indicator (;npdi=yes) between the user and host portions of the URI in the To: header in outgoing SIP messages. NPDI indicates that a query to the Number Portability Database (e.g. the LRN Database) has been completed. This field can be included in order to prevent subsequent lookups in legacy-style PSTN databases. This feature is rarely used.