Getting Facebook email/email hash

I'll make it short: is it possible to get t开发者_运维知识库he user's facebook email adress (or a hashed email adress), so I can let's say compare his facebook email with his email in my database? I'm trying to get a FacebookUser and then use facebookUser.email_hash but that returns nothing.

---

a similar question has been asked here.

and, I don't think fb api currently gives away the user email addresses.