Browser Notification

Hello, my name is André Neto, I am developing software, and inside it there is an email center, where the user can send an email from within the system and I save this sending data. Now the problem, I need to notify the person who received the email, (it is registered in my system by your email), via a notification of the browser, as facebook does the notifications, and would like to make this notification even though the person is not logged into my system, the server would send that message. Any idea how I can do this is very much accepted! Thank you in advance.