Am I right that there is no back-sync from mailchimp back to wordpress?
So, every email HAS to contain a "manage subscription link". When the user clicks on that, he could change his mailchimp setting. But that don't effect the wordpress settings.
So, the settings in mailchimp and wordpress aren't the same anymore. And when I do a new manual synchronization, the settings that the user did in mailchimp are overwritten.
So, how do you handle this?