Let us tell you how Shopify – Mailchimp integration works.
Every email address you collect on your website, whether that’s through checkout, or the newsletter sign-up form, creates a Customer within Shopify Admin.
Depending on the path taken by a user, this Customer will have different amount of information filled out. If they go through checkout, and select “Accept Marketing”, they will have a lot of details, such as name, surname, email, delivery address, billing address, phone number etc.
If, however, they use the newsletter sign-up form, it will only hold their email address, nothing else.
Every so often (10 minutes or so), Mailchimp checks with your list of Customers on Shopify, and adds any new emails.
Here’s the confusing part.
Because of the way this integration works, these new users are not actually counted as newly signed up, but rather as a new import (as if you added them yourself).
What you are trying to do is called Double Opt-in (https://kb.mailchimp.com/lists/signup-forms/about-double-opt-in). If you want to follow the steps outlined here, it will work only for the newsletter sign-up form (after modifying it heavily), but the checkout sign-ups will be ignored.
What you need to do, is create an Automation within Mailchimp, which is triggered whenever a new user joins the list
This is how such an Automation looks like for one of our other clients. It’s a welcome message which gets send to every new subscriber, regardless of the source (manually added, imported, signed up through a form somewhere else etc).
Here is a guide on creating Automation:
Then, when you get to the Design Email part, select Themes, and in there you will be able to filter the results (what we are looking for is Notifications) and that will reduce the number of results. One of the Themes is a GDPR notification. Select that, modify it however you want and you are good to go.
What do you need to do is create 2 Campaigns with Automation.
1) Welcome Email which tells people they have signed up and can unsubscribe if they’ve done so by accident. (again, there are templates for that).
2) GDPR Notice which will be sent only once (and as such you don’t need Automation), to your whole list. This will allows subscribers to modify their subscription (stay or leave).
There are plenty of ways to accomplish what you want. We believe you already created a new List, which deals with GDPR issue, if not let us know and we might be able to help you.