When your users register for a site /username all welcome emails are sent from the email address specified in the Network Admin email area of Settings in the Network Admin Dashboard.
As part of your business brand and online identity it’s best for this email to be sent from your domain name e.g. support.edutags.net. You could also use this same email address for dealing with your users’ support and sales inquiries.
To enable this you will first need to set up your email accounts associated with your domain. While you can manage your email account through cPanel it is easier to configure your email to work with a mail client such as Gmail or Google Apps