I can understand why you might want people to enter an email address (for validation/more authentic results etc...) and if you're going to take that approach you sell it to your audience - tell them what the benefits are.

Also say that the email address requires validation. I put in a fake address and of-course my vote didn't get counted. If I knew up-front it was to be validated I probably would have entered a correct one.

Having said all that I don't agree with email validation. It doesn't ensure unique votes. Can you explain why you choose it?