I'm going to use big font for this:

I can confirm that the email you got IS FAKE

at this moment in time there is only The Friends & Family Internal Blizzard Alpha (Which im lucky enough to be apart of, only on 1 account tho )

There will be forum announcements when the beta goes live.

If you want to check for your self, look at the message source details, it should come from something like smtp.blizzard.com or something like that.