The server email stands for the email address from which voicemail notifications are sent.
To set the Server Email:
1. Login to the system administration.
2. Navigate to 'Settings: Voicemail'.
3. Under the 'E-mail Settings' group there is a 'Server Email' option.
4. Enter the desired value (e.g. firstname.lastname@example.org) and Click the 'Save' button.