Opt-in checkbox?

Hello!

Is it possible to have a checkbox to pick whether or not to add the user to the list? Presently on our site, we have a single contact form, with a checkbox to opt-in for our mailing list. We find this works better for conversions as we capture people who contact us with questions who otherwise may not have thought to join our list.

Thanks

https://wordpress.org/plugins/easy-sign-up/