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Outgoing ISN dialing is enabled using the sipXecs configuration interface. Go to System / Servers and then select the Registrar service and select the ISN checkbox. Optionally a prefix can be selected that needs to be dialed but will be stripped before the ISN lookup takes place.
The sipXecs ISN redirector plugin performs a native ISN lookup. If you control the DNS server for your domain request that freenum.org delegates the zone for your subdomain <your ITAD number>.freenum.org to you so that you gain full control over ISN mappings.
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