Mailchimp is an email marketing service, sending over 10 billion marketing emails per month on behalf of its users. Mailchimp integrates with all the major e-commerce providers so you can use your purchase data to send personalized campaigns and better understand how your marketing affects your bottom line.
If a subscriber agrees to accept marketing during their checkout, they will be added to Shopify's "Accepts Marketing" list. You can then export this list and import it into Mailchimp.
Just ensure you enable the "Bold Subscriptions" feature to Collect Email Addresses with Bold Subscriptions. Configure this setting to "Customer agrees to receive promotional emails by default" for optimal usage.
If you have any further questions on setting up Mailchimp, please contact their Support team.
Visit View and Export a List of Customers Who Accept Marketing for detailed instructions.