How can we retrieve the email details mentioned by the voters. We need to create a database of emails to send out newsletter later. Is retrieval only possible if the voters confirm their email or otherwise as well?
In the advanced step in the »Allow voting« section you can add additional attributes. These attributes can be anything you like. In your case I would add a e-mail field and maybe a checkbox »Yes, I want to subscribe to…«.
The confirmation sends out a email to verify that the user is using a email address he or she has access to. This might be needed for collecting email addresses for newsletters. But the legal requirements here vary from country to country. In any case, you have all options.