martinyoung

Let me see if I understand your question. You have a number outside of your PBX that is being forwarded or transferred in some fashion to a DID that does ring in your PBX. Once it rings into your PBX you are redirecting it again to a third number that is covered by a Cover Answer Group. If this group fails to answer, you want the call to go to the voice mail of the third number in this chain.

If this is correct and the trunk group is an ISDN trunk group it can be easily done on the third page of the trunk group form titled "Incoming Call Handling Treatment". The Service/Feature would be "public-network", called length "4", called number is the last four digits of the DID, del 4, insert the four digit station number you want to use.

The above answer assumes you are getting four digits from the vendor. If you are getting more or less, you will need to make some adjustments to the digit manipulation.

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Marty
Retired Avaya DSIC tech