I am building a product that works automatically for all the people "inside" an e-mail domain. So everybody that's a part of @yesgraph.com would have access to all of the content from other people with the @yesgraph.com e-mail address.
I'd recommend just asking the user to confirm the email domain they care about. I solve this on YesGraph's registration page indirectly just by making the entry field label "work email". https://www.yesgraph.com/signup/