MailChimp for Ninja Forms 

ninjaforms.com...
The Ninja Forms + MailChimp add-on has been tailor-made to offer you the perfect integration between MailChimp and WordPress, effortlessly.
Just add a Mailchimp action to any Ninja Form, choose the mailchimp list you would like data to be sent to, map fields from your form to the appropriate mailchimp list fields, optionally choose any relevant interest groups, choose if you would like users to confirm their subscription, and even add a mailchimp opt in field to give your user the ability to choose if they would like to be added to a mailchimp list.
Eliminate the common pains of email and invest quality. Get Mailchimp for Ninja Forms, today.