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

Akshar Soft Solutions

Plugin allow you to integrate your Memberpress Plugin with Campaign Monitor optin
Usage
Basic usage
Once you have installed and activated the plugin, navigate to Memberpress, Settings, Marketing. You will find Campaign Monitor in list. 
Enable Campaign Monitor and enter your API Key and save changes. After that you will see your Campaign Monitor List in Edit Membership Advanced tab. Select appropriate list and label also you can put legal notice for optin if required.
IMPORTANT NOTES
This plugin sends data to Campaign Monitor. You can find more details at https://www.campaignmonitor.com/.
Plugin is using API & API Wrapper mentioned at https://www.campaignmonitor.com/api/
<h3>Requirements</h3>
<ul>
<li>PHP 5.3 or higher</li>
</ul>
<h3>Translations</h3>
<ul>
<li>None</li>
</ul>

AS MemberPress Campaign Monitor Integration

Integrate Campaign Monitor Optin with your Memberpress Plugin

Simple Membership MailChimp Integration vs AS MemberPress Campaign Monitor Integration