I´m looking for a comfortable way to realize double opt-in via mailchimp API 3.0. It looks like there was an option in version 2.0 which told m
When using Double Opt In on a list, people who have filled out your signup form will have an API status of pending until they confirm their subscription.
In order to mimic that functionality in API v3.0, set the user's status to pending instead of subscribed in your POST call. See How to Manage Subscribers for more details.