The Mailchimp integration automatically adds form submitters to your Mailchimp email list every time someone submits a form. This eliminates the manual process of exporting CSV files and importing them into Mailchimp. It is essential for lead generation forms, newsletter signups, event registrations, and any form where you want to follow up with email marketing.
Every form submission that includes an email address is a potential subscriber. The Mailchimp integration ensures that potential is captured automatically, without you lifting a finger after the initial setup.
What You Need Before Starting
- A Mailchimp account (free or paid plan)
- At least one Audience (email list) already created in Mailchimp
- Your Mailchimp API key
Setup Walkthrough
Step 1 — Get Your Mailchimp API Key- Log in to Mailchimp at mailchimp.com.
- Click your profile icon in the bottom-left corner and go to Account & Billing.
- Navigate to Extras > API Keys.
- Click Create a Key. A new API key is generated.
- Copy the key immediately (you will not be able to see it again after leaving the page).
- In WordPress, go to Fillin Forge > Settings (the Mailchimp card).
- Paste your Mailchimp API key into the API Key field.
- Click Connect. Fillin Forge checks the key and stores it by itself, so you do not need to click Save Settings for it. The page shows “Mailchimp connected successfully.”, and the card then shows “Connected to Mailchimp” with your account name and a Disconnect button. Your API key is stored on the Forge API server, not in your WordPress database.
- Open the form you want to connect (or create a new one).
- Find the Mailchimp card in the builder.
- Toggle on Subscribe to Mailchimp list on submission.
- Enter the List ID of the audience you want to subscribe people to. In Mailchimp you find it under Audience, Settings, Audience ID.
- Under Email Field, pick the form field that contains the subscriber’s email address, or keep Auto-detect email field. The dropdown only lists fields whose type is Email, so add an Email field first if the dropdown is empty.
- Other fields cannot be mapped to Mailchimp merge fields in the builder: the email address is what gets sent.
- Save the form.
How It Works
- Every time someone submits the form, your site sends their email address to our API (api.avakode.com), and our API passes it on to Mailchimp.
- If the email address is already on your list, no duplicate subscriber is created: Fillin Forge asks Mailchimp to add the address as “subscribed” only when it is new. A contact that is already on the list keeps the status it has, including “unsubscribed” and “pending” (a double opt-in that is not confirmed yet), and no other information of that contact is changed.
- New subscribers are added with a “subscribed” status immediately.
- The form submission is also saved in Fillin Forge as usual. The Mailchimp sync is an additional, automatic action.
- If Mailchimp rejects the request, the visitor still gets the normal success state and Fillin Forge records a diagnostic entry for support instead of losing the submission.
Troubleshooting Mailchimp
| Problem | Most likely cause | Solution |
|---|---|---|
| Subscribers not appearing in Mailchimp | The wrong field is chosen as the Email Field, or the submission has no valid email address | In the Mailchimp card, check the Email Field dropdown (or keep Auto-detect email field) |
| “API key invalid” error | Key was regenerated or revoked in Mailchimp | Create a new API key in Mailchimp and reconnect in Fillin Forge |
| Name or other fields are empty in Mailchimp | Fillin Forge sends only the email address; the builder has no merge-field mapping | Read the other answers in the Fillin Forge submission |
| Wrong audience receiving subscribers | Wrong List ID in the form’s Mailchimp card | Edit the form’s Mailchimp card and enter the correct List ID |
| Subscriber shows as “cleaned” | The address has the status “cleaned” in Mailchimp. Fillin Forge never sets this status: for a new address it asks for “subscribed”, and for an address already on the list it sends no status at all, so the status stays as it is | Check the contact in Mailchimp. If Mailchimp refuses the request, Fillin Forge records the error and the submission is still saved |
| The Email field dropdown is empty | The form does not have an Email field type yet | Add an Email field to the form, save, and return to the Mailchimp card |
| Submission is saved but the diagnostic log says “Invalid request” | The integration request was rejected before Mailchimp received it | Update to the current Forge API build; empty merge-field maps are normalized and the subscriber hash is generated server-side from the lowercase email |
> Tip: Test the integration by submitting the form with your own email address. Check Mailchimp to confirm the subscriber appeared in the correct audience.
> Good to know: Without PRO, the Mailchimp integration is not available. You can export submissions to CSV (free) and manually import them into Mailchimp, but this requires manual effort each time.
Common Mistakes to Avoid
- Forgetting to create a Mailchimp Audience before connecting. You need at least one audience for the integration to work.
- Expecting the subscriber’s name or other answers in Mailchimp. Fillin Forge sends only the email address, so you cannot personalize your emails with the subscriber’s name from this integration.
- Connecting Mailchimp in Settings but forgetting to enable it on the specific form. Both steps are required.
[Screenshot: The Mailchimp card of the form builder showing the toggle, the List ID field and the Email Field dropdown]
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