Mailchimp

Turn browsing guests into an email audience you own. This app loads Mailchimp's connected-site script, which shows the pop-up signup forms you design in Mailchimp and adds subscribers straight to your audience.

In Mailchimp, go to your audience's Signup forms > Connected sites pop-up form, copy the script URL from the embed code (the https://chimpstatic.com/... address), and paste it into the app settings.