This action subscribes a contact to a Mailchimp audience (previously referred to by Mailchimp as a "list"). If they aren't an existing contact in Mailchimp they will be added as one.
To use this action you need to connect to Mailchimp in Settings. Once connected, you could create a Journey such as this one:
Why do contacts sometimes take a while to be subscribed to a Mailchimp audience?
While we try to process things as quickly as possible for you, we are ultimately subject to Mailchimp's API limits. Please bear this in mind, particularly if we are using this action to perform mass updates.
The contact feed says "Mailchimp wouldn't accept" my contact, what does this mean?
Sometimes you might see this in a contact's feed when you try to subscribe them to a Mailchimp audience:
This is part of Mailchimp's protection against fake signups. You are welcome to try subscribing the contact again, however it is ultimately up to Mailchimp whether to accept the contact. Please contact Mailchimp's support team if you think a contact is being rejected when they shouldn't be.