i don't know if i understood ur question well..

if u meant what is the usefullness of VM entire the corporate, indeed one of great avails of VM is that it may laver the interactivity and facilitate reachibility for employees to each other, if it is activated to be forwarded to VM in these states:

call no answer/unavaiable

call busy

so after x rings without answer by the called party the caller will be transferred to called party's VM to leave a message, the same thing in case of the called party's state is busy...

hth

please remember to rate helpful posts

/majdi