Remember that telephone usage varies greatly between companies. For instance, salesmen and traveling executives use voice mail and email reading much more than engineers or non-traveling clerical staff. Therefore the number of ports required for a given size company is not an exact table lookup.
If a company already has a voice mail system, PhoneSoft will use the same number of UMC ports as the voice mail system it is replacing. This is the best guide for determining UMC port requirments. If the company does not currently have a voice mail system, the table below is a good cross-industry average.