In the Umbraco form, there are different workflows available to set up a process to submit the form like send an email, set up Thank you message, etc. I have created a custom workflow to integrate the MailChimp list to subscribe user.
You just need to add API key, Subscriber list Id and MailChimp fields with Umbraco form fields using the mapper.
This package is available in Umbraco v8 and Umbraco v7 also.
Download package using NuGet package and from the Umbraco package.
then you get MailChimp workflow in the list and use that directly.
Please let me know your reviews, any issue with this package, or any kind of issue in Umbraco, asp.net MVC. I would like to help you. Contact me at [email protected]