If you are using both MailChimp and the built in SimpleClinic Marketing Automation, it is very important to read the following information regarding opt out. 

If you are sending MailChimp campaigns to an audience list, e.g. list Id 1234, and sending a campaign through the SimpleClinic Marketing Automation to a different list, e.g. list id 5678, any contact who opts out using a link from a MailChimp campaign WILL NOT BE OPTED OUT of SimpleClinic Marketing Automation campaigns and vice versa. 

More detail regarding MailChimp's handling of audiences and opting out 

This is because MailChimp audiences (and in turn webhook notifications) are linked to specific listIds (what MailChimp calls audiences). This is unlike other providers. This is how the current SimpleClinic integration with MailChimp works and will continue to work. 

If a contact unsubscribes or is unsubscribed from a specific audience (listId) in MailChimp it does not affect other audiences. You can read more about this from MailChimp here: https://mailchimp.com/help/about-unsubscribes/

This is the default way MailChimp handles multiple lists and they view this as a feature. You can read more about this from MailChimp here: https://mailchimp.com/help/about-unsubscribes/ 

MailChimp’s recommendation is that clinics should have one primary audience and use tags to segment their contact base and not have multiple audiences.

Please contact support@simpleclinic.net if you need further assistance.