Regroup gives you the ability to suppress the entire network from sending emails to secondary emails.
First navigate to your Network Settings page by clicking on your Avatar in the top right corner of the page. Choose "Network Settings"
Once on the General Settings page you will choose "Access" from the left menu
Once on the "Access Setting" page you will scroll down to "Send Email" check this box and now emails will only be sent to the primary email address of all contacts.