Normally in the 4000 world the system checks to see if it CAN forward a phone before it tries. If that phone is out of service the call normally will not forward and will simply ring on the forwarded phone until the caller hangs up or the call is answered. BUT .... If you specify the forwarding criteria for when the phone is in DND mode it will also forward to that same crietia if the phone is out of service for whatever reason. If you have DND forwarding criteria specified for a phone, and you do not want that phone to forward if it is out of service, you should be able to remove the DND forwarding criteria and you will achieve your desired response. Second BUT .... If the phone is variably call forwarded (like when the user activates call forwarding) it will still follow that forwarding path if the phone is out of service (as I use that functionality quite often).
Hope something in there helps you!
Don Bruechert, Voice Comm Analyst II
CareTech Solutions @ Holy Family Memorial
Manitowoc, WI, USA