When you run a contest it is pretty common that you receive a lot more voter contacts than you do entrants or registered users. This information is a create source of contacts for you to market to. However in order to ensure you comply with Privacy laws such as GDPR you need to ensure you receive consent before you use this information for anything other than tracking votes for winners.
So to help you do this we have a "opt-in" checkbox that can be added to the voting dialog box when voters supply personal information such as email address when voting.
To set this up go to the voting section in the contest settings.
Then select "User validation" and then either Email or Social verification and also select "Include voting opt-in checkbox with terms and conditions".
After this is setup, whenever someone is voting they will have the option to opt-in to your list. This will also be automatically audited with the date and time they provided consent as well as the link to the policy documents.