do nothing and just delete it. clicking on any links within the email could have consequences. I get them all the time but fortunately they are using an email address not associated with itunes.
I received this "receipt" supposedly from iTunes.. BUT the return address was email@example.com
It was for a Ppm One Cluck Professional, VpnOneClick 12 months for $36.99 with a link to "report a problem"... to report you need to give your apple ID AND PASSWORD!