Your Mailchimp audience is the authority on who wants to hear from you. When someone unsubscribes there, your store honors it, automatically and permanently. The extension keeps a clear division of duties: Mailchimp rules the audience, your store rules the shop. Orders, products and carts flow from Magento to Mailchimp; consent decisions flow from Mailchimp to Magento. Each side is the source of truth for what it owns, and neither ever overwrites the other’s judgment.
Audience decisions that flow back
| What happens in Mailchimp | What changes in your store |
|---|---|
| Someone unsubscribes from an email | Marked as unsubscribed in Magento newsletter |
| An email hard-bounces and gets cleaned | Marked as unsubscribed in Magento newsletter |
| Someone resubscribes via a Mailchimp form | Reactivated as a subscriber in Magento |
| A contact updates their email address | Newsletter subscriber email updated. The customer’s store account email is deliberately untouched, so nobody’s login changes because of a marketing edit |
That short list is deliberate. Consent belongs to Mailchimp, so consent decisions come from Mailchimp; your Magento newsletter list follows their lead, a faithful mirror rather than a second authority. Everything else about your shoppers stays exactly as Magento has it: profile edits made in Mailchimp are never written into your store.
Mailchimp explains what cleaned contacts are if you need a refresher.
An opt-out in Mailchimp is final as far as the extension is concerned. It marks the contact unsubscribed in Magento, and no sync, catch-up or re-sync will ever re-subscribe them; the sync corrects the store’s records to match Mailchimp, never the other way around. Only a genuine new action, the shopper subscribing again themselves, can bring someone back.
This is the same promise that protects your audience everywhere in the extension: it adds and updates, it never takes away, and it never argues with Mailchimp about consent.
How the changes arrive
Mailchimp notifies your store the moment something changes, through a webhook the extension registers automatically when you complete the Setup Wizard. Changes are applied as soon as they arrive, usually the same moment. There is nothing to configure and nothing to maintain: if you ever reconnect the store, the extension re-creates its webhook on its own. Your store only needs to be reachable over HTTPS, which it already is if shoppers can reach it.
This webhook is the only inbound door the extension opens on your store, and it is built like it knows that. Every message must present a secret key, unique to your account and stored encrypted, before anything else happens. It must then pass a strict checklist: the right format, a strict size limit, and only the handful of event types the extension expects. Anything else is turned away at the door, and floods are rate-limited before they can put any load on your store. Even a valid message can only ever do one small thing: update a newsletter status or an email address. It cannot touch settings, files or anything else. And the key can be renewed at any time, without missing a single notification.
Mailchimp’s notifications need to reach one address on your store: the webhook address the extension registers. If your store sits behind a firewall or a web application firewall, add that address to its allow list; your host or CDN dashboard is the usual place. And you are never left guessing: the extension checks the address the moment it registers the webhook, and if Mailchimp cannot get through, the Webhooks page in your admin says so plainly, with the reason.
What flows the other way (store to Mailchimp)
This is Magento exercising its side of the division: a shopper subscribing or unsubscribing on your store is a genuine new action, so it flows up to Mailchimp.
- A shopper opts in to your newsletter at checkout or on their account page → synced to Mailchimp as subscribed.
- A customer unsubscribes from your Magento newsletter → synced to Mailchimp as unsubscribed.
Mailchimp’s notifications are applied on arrival, cron or no cron. The store-to-Mailchimp direction runs on Magento’s background scheduler, and the Cron Monitor shows it working, job by job.
Questions along the way? Troubleshooting has the answers, and ebizmarts support is one email away.