Please note - this supports up to concrete 5.6, for 5.7 onwards please refer to https://marketplace.concretecms.com/marketplace/addons/mailchimp-integration/
Mailchimp is a full featured and cost effective email delivery, analysis and list building service. It is ideal for newsletters, targetted marketing and much more. It safely manages the process of building your list whilst complying with privacy regulations. It also dedicates itself to ensuring your emails get through to your customers inbox.
This addon enables you to have a capture form on your website which sends the data through to your mailchimp.com account. It allows your users to specify which lists they wish to register with based on the ones you have selected.
To use this addon, you need to create an account with Mailchimp at www.mailchimp.com. They have free and paid-for accounts available. depending on the size of your list and frequency of mailing - but for many companies, their limits are generous.
Please note there is an issue with Concrete 5.6.0 which stops this plugin from being added to a page. This is the description of how to fix it, or upgrade to 5.6.1 which has the fix applied. https://marketplace.concretecms.com/community/forums/customizing_c5/c5-5.6.0-issue-with-block-controller-and-ajax-request/