Core Issue
In Cisco CallManager 5.1 with Cisco Unity, callers can reach a voice mailbox if they call it directly, but when a call is redirected from an IP Contact Center (IPCC) script to a voice mail pilot, the caller hears a prompt that there is not a voice mailbox configured for the dialed number (DN).
Resolution
Cisco Unity needs the called number to remain that of the CTI RP. When a normal call redirect is performed, the step changes the called number to that of the destination.
In order to resolve this issue, update the Call Redirect step to preserve the called number in the IPCC. Upload it to repository and refresh the application.