The Mailchimp integration that allows to automatically sync and import users registered in a promotion to a Mailchimp list, has been updated with the following improvements:

1. New interface. The configuration interface in the sections Integrations > Mailchimp has been redesigned.
2. Groups/Interests features in a list supported. We've included the option of selecting a Group/Interest in a subscriber list to send the promotion participants to.
3. Tags supported. We've included the possibility to add a Mailchimp tag to all the promotion participants. 
4. Make checking a specific box a condition for importing to a Mailchimp list. You can for example select the checkbox where users give their consent to be included in an emailing list.

On the other hand, the option of synchronizing users who vote in a contest with a Mailchimp list has been eliminated. This is due to the fact that users who vote don't give their explicit consent to being included in an emailing list.

Here you can see the tutorial on how to enable the Mailchimp integration in your promotion.