Should you wish to send multiple emails to external recipients, under the Notify email field, type ";" in between emails. 

Should you wish to just notify your internet staffs or any email address for every statuses update, you can go to Settings > Notifications > Notification section> click on Events (completed partially completed | failed).  Scroll down to Email section. Under Other fixed emails, enter the email address you wish to inform. For more than one email address you can enter the next line (One per line) and click Save