Freemius MailChimp Integration & Seamless Checkout

Release Notes is our monthly update that highlights the recent product improvements we’ve made, so you can easily stay up to date on what’s new. Here’s what we launched in May. This product cycle was focused on three main objectives:
Integration with 3rd party email marketing services
Improving the in-dashboard upgrade process for freemium products
User-friendly usage tracking terms
MailChimp Integration
Since our early days, we released a webhooks mechanism, because we know it’s impossible to develop every feature in-house and address every use-case. A solid webhooks mechanism makes Freemius more powerful and extensible and allows developers to integrate the platform with practically any 3rd party service.
Over the past year, we learned that the #1 (by far) usage of the webhooks mechanism was for integrating Freemius with MailChimp, powering up the email marketing efforts with our high converting opt-in. At first, we created an example of a vanilla PHP Webhook integration. Though some WordPress developers in our community had a lack of sysadmin knowledge for taking and deploying it to their WordPress powered site. A collaboration between two of our developers
Source: https://managewp.org/articles/15152/freemius-mailchimp-integration-seamless-checkout

source https://williechiu40.wordpress.com/2017/05/18/freemius-mailchimp-integration-seamless-checkout/