Krom Automation Pro connects to Mailchimp, giving you one trigger and five actions that cover the most common Mailchimp automation needs: subscribing contacts to audiences, applying and removing tags, updating member data, and receiving Mailchimp webhook events back into WordPress.

An API key is required. Setup takes under two minutes.

Requirements #

• Krom Automation Pro installed and activated
• A Mailchimp account (free or paid)
• A Mailchimp API key

Configuration #

1. Log in to your Mailchimp account.
2. Click your account avatar in the top right, then go to Account & billing > Extras > API keys.
3. Click Create A Key, give it a name like Krom Automation, and copy the key.
4. In your WordPress admin, go to Krom Automation > Settings.
5. Find the Mailchimp settings section and paste your API key into the API Key field.
6. Click Save.

Screenshot: Mailchimp API keys page with a key generated and highlighted.

Screenshot: Krom Automation Settings page with the Mailchimp API key field filled in.

Krom Automation connects to Mailchimp immediately after saving. No additional OAuth or redirect steps are needed.

Available trigger #

Webhook Received

Fires when Mailchimp sends a webhook event to your WordPress site. Mailchimp can send webhooks on subscribe, unsubscribe, profile update, email address change, campaign sending, and other account events.

Data field	Description
event_type	The type of Mailchimp event (e.g. subscribe, unsubscribe, profile)
email	The subscriber’s email address
first_name	Subscriber first name
last_name	Subscriber last name
list_id	The Mailchimp audience ID the event relates to
reason	Reason for the event (e.g. unsubscribe reason)

Setting up the Mailchimp webhook:

To receive Mailchimp events in Krom Automation, you need to configure a webhook in Mailchimp pointing to your site.

1. Create a workflow in Krom Automation using the Mailchimp Webhook Received trigger.
2. Activate the workflow.
3. In Mailchimp, go to Audience > Manage Audience > Settings > Webhooks.
4. Click Create New Webhook.
5. Enter the Krom Automation webhook receiver URL for this workflow. Find this URL in the Krom Automation workflow settings panel.
6. Select which Mailchimp events to send.
7. Save the webhook in Mailchimp.

Screenshot: Mailchimp webhook creation screen with the Krom Automation URL entered in the callback URL field.

Common use: Triggering a WordPress action when someone subscribes or unsubscribes in Mailchimp — for example, updating a WordPress user’s role when they unsubscribe from your list, or granting access to gated content when they join a specific audience.

Available actions #

Subscribe

Adds a contact to a Mailchimp audience. If the contact already exists in the audience, Mailchimp updates their record instead of creating a duplicate. This is an upsert operation — safe to use on contacts who may already be subscribers.

Field	Required	Description
audience_id	Yes	Your Mailchimp Audience ID. Find this in Mailchimp under Audience > Settings > Audience name and defaults.
email	Yes	The subscriber’s email address. Use {{user_email}} or {{customer.email}} as appropriate.
first_name	No	First name. Use merge tags to pass the name from the trigger.
last_name	No	Last name.
status	No	The subscription status: subscribed, pending (sends a confirmation email), or unsubscribed. Defaults to subscribed.

Unsubscribe

Sets a subscriber’s status to unsubscribed in a Mailchimp audience. This does not delete the contact — it marks them as unsubscribed so Mailchimp will not send them campaigns.

Field	Required	Description
audience_id	Yes	Your Mailchimp Audience ID.
email	Yes	The subscriber’s email address.

Common use: Unsubscribing a customer from a Mailchimp audience when their WooCommerce Subscription is cancelled or a MemberPress membership expires.

Add Tag

Applies one or more tags to an existing Mailchimp subscriber. Tags must be separated by commas if adding multiple at once. If a tag doesn’t exist in Mailchimp yet, it is created automatically.

Field	Required	Description
audience_id	Yes	Your Mailchimp Audience ID.
email	Yes	The subscriber’s email address.
tags	Yes	One or more tags to apply, separated by commas.

Common use: Tagging a subscriber when they complete a LearnDash course, purchase a specific WooCommerce product, or reach a milestone in their membership.

Remove Tag

Removes one or more tags from a Mailchimp subscriber.

Field	Required	Description
audience_id	Yes	Your Mailchimp Audience ID.
email	Yes	The subscriber’s email address.
tags	Yes	One or more tags to remove, separated by commas.

Update Member

Updates merge fields (custom data fields) for an existing Mailchimp subscriber. Use this to keep subscriber profile data in sync with WordPress.

Field	Required	Description
audience_id	Yes	Your Mailchimp Audience ID.
email	Yes	The subscriber’s email address.
Merge fields	No	Any Mailchimp merge field you want to update (e.g. FNAME, LNAME, PHONE). Use your Mailchimp audience’s actual merge field tags.

Common use: Updating a subscriber’s name or phone number in Mailchimp when they update their WordPress user profile.

Setting up your first Mailchimp workflow #

1. Go to Krom Automation > Workflows and click Add New Workflow.
2. Choose a trigger. For most Mailchimp workflows, this is a WordPress event trigger (User Registered, WooCommerce Order Completed, LearnDash Course Completed, etc.).
3. Click + to add an action and select Subscribe or another Mailchimp action from the Mailchimp category.
4. Enter your Mailchimp Audience ID and map the email field to the appropriate merge tag from your trigger.
5. Add any optional fields like first name, last name, or tags.
6. Simulate the workflow to confirm the action would execute correctly.
7. Activate.

Screenshot: Krom Automation canvas with a WooCommerce Order Completed trigger connected to a Mailchimp Subscribe action, with the audience ID and email field configured.

Real-world automation examples #

Subscribe WooCommerce customers on first purchase Trigger: WooCommerce Customer First Purchase Action: Mailchimp Subscribe using {{customer.email}}, {{customer.first_name}}, {{customer.last_name}}, with status subscribed and your post-purchase audience ID.

Tag subscribers on course completion Trigger: LearnDash Course Completed Action: Mailchimp Add Tag to the subscriber using {{user_email}}, tagging them with the course name or a completion tag.

Unsubscribe on membership cancellation Trigger: MemberPress Subscription Cancelled Action: Mailchimp Unsubscribe using {{user_email}} from your active members audience.

Subscribe new WordPress users Trigger: User Registered Action: Mailchimp Subscribe using {{user_email}}, {{first_name}}, {{last_name}}, with status pending so they receive a confirmation email before being added.

Sync profile updates to Mailchimp Trigger: User Profile Updated Action: Mailchimp Update Member using {{user_email}} with FNAME set to {{first_name}} and LNAME set to {{last_name}}.

Pre-built templates #

Install these from Krom Automation > Templates:

Template	What it does
mc-user-registration-subscribe	Subscribes new WordPress users to a Mailchimp audience
mc-woo-purchase-subscribe	Subscribes WooCommerce customers to Mailchimp on purchase
mc-form-submit-subscribe	Subscribes form submitters to a Mailchimp audience
mc-course-complete-tag	Tags a Mailchimp subscriber when a LearnDash course is completed
mc-webhook-segment-tag	Applies a tag when Mailchimp sends a webhook event to WordPress

Troubleshooting on Mailchimp integration #

The Mailchimp Subscribe action is failing in the execution log

Check the error message in the step detail. The most common causes are an incorrect Audience ID, an invalid API key, or an email address already marked as permanently bounced in Mailchimp (Mailchimp does not allow re-subscribing permanently bounced addresses via the API).

I’m using status: pending but subscribers are not receiving a confirmation email

Mailchimp only sends the confirmation email if double opt-in is enabled on the audience. Check your Mailchimp audience settings under Audience > Settings > Form settings. If double opt-in is disabled, pending status contacts are added without receiving a confirmation.

My Audience ID is wrong — where do I find it? In Mailchimp, go to Audience > All contacts, then click Settings > Audience name and defaults. Your Audience ID appears on that page. It’s a string of letters and numbers, not the audience name.

Tags are not appearing on the subscriber in Mailchimp

Confirm the subscriber exists in the audience before applying tags. The Add Tag action requires the contact to already be a member of the audience. If they’re not yet subscribed, add a Subscribe action before the Add Tag action in the workflow.