This is the default behavior with CCM and Unity. Are you using these or other products. There is a setting in Unity which can change this behavior. It could have been changed with your installation. The setting is located in the Advanced Settings Tool in the Tools Depot and is called "Route by last redirecting ID".
Once the call leaves the jurisdiction of the CUCM it no longer has control of that call. The caller will end up wherever the external extension sends it(for example: Cell Phone Voice mail). However, the user Cell Phones can be set up to use your Unity as their Voice mail destination, which would solve your problem.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...