Motivation:

You call. There is no answer. You leave a Voice Mail (VM). Now if you only had an indication that your VM was retrieved by the called party, you would know he or she got the memo, and therefore there is no need to send an email/text message or call again.

The feature:

The VM server (AKA Unified Messaging server) can (as a dependency of the privacy policy of the mail box owner) notify the caller upon Voice Mail retrieval. From marketing perspective this feature is about saving extra calls and/or extra text messaging, meaning reducing traffic. This seemingly may hurt the pocket of the network provider. However, at the same time it may increase the happiness of the user with the service, hence its attraction to that particular provider. Definitely something to think about...

How this can be accomplished:

Figure 1 below illustrates how this can be accomplished.