The Dotdigital for Magento connector synchronises your contact data with three different address books for three different types of users of your site - customers, subscribers and guests.
How data syncing works
As explained in the article Magento 2 databases and cron services, this process works by contacts being batched from the Dotdigital email_contact tables and inserted into the email_importer table. From there, the importer cron processes all batched data from the importer and sends it to your Dotdigital account.
Before any synchronisation can begin, however, you'll need to create these address books in your Dotdigital account so they can be selected and mapped to from within the connector.
In addition to setting up address books, you will want to create and map contact data fields too. This is simply the mapping process enabling us to sync Magento data to contact data fields you have created in Dotdigital. The articles in this section explain how.
Everyone is synchronised, which includes contacts who decide to unsubscribe from your store. Therefore, to be clear, such unsubscribed contacts will be removed from your Magento subscribers address book only; their status will remain as subscribed in your Dotdigital account.