Each and every social network by default sends an intimation mail of any new activity or update on your network. Although it is a useful feature, due to increased number of users, notifications about multiple updates in a day ends up clogging your email.
You can disable email notifications from any social network, but that would require hunting for the specific setting page. A simpler solution is to head to www.notificationcontrol.com - a website with a single page that has links to various social networks.
Each link opens the exact setting page where the option to disable email notifications is of the selected social network. Uncheck the option for notification mails and you are set.