Hi Naushad,
You can have either a separate (dedicated) PSTN number for this specific purpose (which is routed to the voice mail pilot number), or these calls can use your main business number (and therefore terminate on the AA). If you choose to terminate calls at the AA, you must redirect calls to voice mail via the AA menu by dialing the voice mail pilot number as an extension.
If a subscriber wants to call in to check voice mail from any off-net location (such as home or a cell phone) and to be presented only with the PIN login menu (and not the User ID followed by PIN login menu), then Cisco Unity Express must recognize the caller ID delivered with the PSTN call and be able to map that to a mailbox on the system. This call flow requires the following:
•The PSTN must deliver caller ID to your location.
•You must associate a secondary number (the PSTN phone number) with the mailbox in addition to the extension.
You can associate a secondary number with a Cisco Unity Express mailbox by setting the Primary E.164 Number field in the user's profile to this number
From this excellent CUE doc;
http://www.cisco.com/en/US/docs/voice_ip_comm/unity_exp/design/design21/cuevmdes.html#wp1008337
Hope this helps!
Rob
