How do I sync unsubscribes with Mailchimp?

In order to pull your Mailchimp unsubscribes into MageMail, add your API key and list ID into the settings under Settings > Integrations:

It will import roughly 1k to 2k unsubscribes every hour until it grabs all of them. If you would like to also export your MageMail unsubscribes to Mailchimp (i.e. a 2 way sync), you can enable that here:

Here's where you can find your list ID in Mailchimp: