Hey lawkwok,
I see what you mean now, thanks for clarifying. When you say ‘duplicates’ I’m not sure if you mean duplicate checkboxes or duplicate MailChimp subscribers, but I can answer each one:
Regarding duplicate checkboxes: To clarify some the checkbox allows folks to choose to opt-in to your MailChimp list when they make a purchase. When that box is checked and someone makes a purchase, your customer is added to the ‘subscribed’ portion of your list and are eligible to receive campaigns. If the box is unchecked and someone makes a purchase, they are added to the ‘transactional’ portion of your list. They won’t be eligible to receive campaigns and cannot be exported, but their e-commerce data will be preserved in their profile in MailChimp. If the checkbox is not present there wouldn’t be a way for a customer to opt into or out of receiving campaigns from your list. For this reason, there wouldn’t be a way to disable the checkbox.
Regarding duplicate email addresses: Subscribers on a MailChimp list are considered unique by email address. This means that if they are passed back to the same list twice, we wouldn’t add them in duplicate. If they were passing over to separate lists, however, they would be considered unique for each list and be duplicated across the whole account.
We would recommend using the MailChimp for WooCommerce plugin solely, rather than multiple plugins designed to pass WooCommerce data over to MailChimp. This can help avoid conflicts with passing data and prevent duplicates across lists.
Thanks again for your post, and please let me know if I can provide any more info!
-Garnet