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

rajasekharan

This plugin is used to create new autoresponder subscribers in WP Autoresponder automatically when a new subscriber is added to any one of the levels in the s2member membership website plugin.

s2member to WP Autoresponder Integration Plugin

Plugin to create new subscribers in WP Autoresponder when new members of s2member are created.

Simple Membership MailChimp Integration vs s2member to WP Autoresponder Integration Plugin