There's also the privacy aspect to consider. Paper telephone messages can be read by anyone - you may not want other people to see who has been calling you, what their phone numbers are, and what the messages say. PhonePad keeps all of your messages neatly together in its Inbox that can only be accessed by you. PhonePad is ideal for Receptionists. They can take messages for staff and send them to the particular person's Inbox.
Receptionists can also check for messages in other users' Inboxes.
And PhonePad doesn't need an email system to work. It is totally independent of any messaging systems. This means that if the email system goes down, PhonePad continues to work. It also means you don't have to have an email system to use PhonePad. All PhonePad needs is a drive that is shared between users who want to be able to send PhonePad messages to each other.