MC4WP: Mailchimp for WordPress

MC4WP: Mailchimp for WordPress, The #1 (unofficial) Mailchimp plugin. Allows you to add various sign-up methods to your WordPress site.. It was authored by ibericode. It currently has around 1,430 starts, 49 support threads and 42 support thread resolved, 45,294,237 downloaded and installed by 2+ million users.