wp.insider

smp7

This addon allows you to specify a MailChimp list name for each of your access levels. When members join your site, they get signed up to the specified MailChimp list.
This addon requires the <a href="https://wordpress.org/plugins/simple-membership/" rel="ugc">simple membership plugin</a>.
After you install this addon, edit your membership level and specify the mailchimp list name. Then go to the MailChimp settings interface and specify your API Key.
Read the following page for step by step usage documentation: 
https://simple-membership-plugin.com/signup-members-mailchimp-list/

Simple Membership MailChimp Integration

An addon for the simple membership plugin to signup members to your MailChimp list

Simple Membership MailChimp Integration vs Email Subscribers & Newsletters – Powerful Email Marketing, Post Notification & Newsletter Plugin for WordPress & WooCommerce