Subscribe to Mailchimp

Audience: Low-code Engineers

Skill Prerequisites: Mailchimp account, Tokens

Adds an email address to a Mailchimp audience (list), or updates it if it's already there. You can also send merge field values, such as first and last name, and add the subscriber to interest groups.

note

The Mailchimp actions require the Mailchimp feature to be licensed. They use the Mailchimp Marketing API v3.0.

Typical Use Cases

• Add newsletter sign-ups from a form to a Mailchimp audience
• Subscribe new customers during registration or checkout
• Keep merge fields, such as name or company, up to date in Mailchimp
• Add subscribers to interest groups chosen on a form, for example the topics they want to hear about

Don't use it to

• Update GDPR marketing permissions. Use Update Mailchimp Member instead.
• Unsubscribe someone. This action always sets the member to subscribed.
• Import large lists. Each run sends one address. Use Mailchimp's import tools for bulk loads.

Related Actions

Action Name	Description
Update Mailchimp Member	Updates a member's GDPR marketing permissions.

Input Parameter Reference

Parameter	Description	Supports Tokens	Default	Required
API Key	Your Mailchimp API key, for example 0123456789abcdef-us21. Create one in Mailchimp under Account > Extras > API keys. The part after the dash tells the action which Mailchimp data center to use.	Yes	empty string	Yes
List Name or Id	The audience to subscribe to. The action first treats the value as an audience ID, then looks for an audience with exactly this name. Name matching is case-sensitive.	Yes	empty string	Yes
Email Field	The email address to subscribe. In forms, select an email field. Elsewhere, such as in workflows, automation or APIs, enter the address or a token such as [Email].	Yes	none selected	Yes
List Data	Merge fields to send. In each row, enter a field ID from the form or context in the first column, and the Mailchimp merge tag in the second, for example FirstName → FNAME or CompanyField → MMERGE3. Rows with an empty column are skipped.	Merge tag column only	empty	No
Interests	Interest groups to add the subscriber to. Enter the interest names in the second column, separated by commas or semicolons, for example [TopicsCheckboxList]. See How interests are matched.	Yes	empty	No
Double Optin	When checked, a new subscriber is added as pending and Mailchimp sends a confirmation email. When unchecked, new subscribers are added as subscribed straight away. Only skip double opt-in if you have consent another way; misuse can get your Mailchimp account suspended.	No	Unchecked	No
Continue on error	When checked, a failure is logged and the following actions keep running. When unchecked, a failure stops execution.	No	Unchecked	No
Enable debug	Not used. It has no effect.	No	Unchecked	No

Output Parameters Reference

Parameter	Description
Error token name	Optional. The name of a token that receives the error message if the action fails. It's set whether or not Continue on error is checked.

How the subscriber is updated

• New address: the member is created with the merge fields and interests you provide.
• Existing member: the member's current details are kept and the values you provide are added on top. Interests are only ever added, never removed.
• Previously unsubscribed member: the member is resubscribed. Make sure you have the person's consent before resubscribing them.

How interests are matched

• Each interest name must match the name in Mailchimp exactly, including capitals.
• The action searches the interests in all of the audience's interest categories (up to 10 categories). The category column in the grid is for your reference only and isn't used for matching.
• Names that don't match any interest are ignored without an error.

Considerations

• Mailchimp errors. If Mailchimp rejects the request, for example because the address is invalid or was permanently removed ("compliance state"), the action fails with Failed to subscribe to Mailchimp followed by Mailchimp's response.
• Audience not found. If no audience has the given ID or name, the action fails with Invalid list followed by the value.
• Invalid API key. A key without a data center suffix fails with API Key is invalid - could not determine endpoint.
• Blank email. An empty address fails with Blank email address.
• Keep the API key safe. Anyone with the key can manage your Mailchimp account. Store it somewhere secure and pass it in with a token rather than typing it into every action.

Examples

tip

To understand how to use the below examples, please see Running Examples.

1. Subscribe a form sign-up with name and interests

This action subscribes the address in the Email field to the Newsletter audience with double opt-in. It sends the FirstName and LastName fields as FNAME and LNAME, and adds the interests selected in the Topics field. If it fails, the error is stored in MailchimpError and the form carries on.

{
    "Title": "Subscribe to Mailchimp",
    "ActionType": "SubscribeToMailchimp",
    "Description": "Add the sign-up to the newsletter",
    "Condition": null,
    "Parameters": {
        "ApiKey": "[MailchimpApiKey]",
        "ListName": "Newsletter",
        "EmailField": {
            "Expression": "[Email]",
            "Value": "",
            "IsExpression": true,
            "Parameters": {}
        },
        "Data": {
            "FirstName": "FNAME",
            "LastName": "LNAME"
        },
        "Groups": {
            "Topics": "[Topics]"
        },
        "DoubleOptin": true,
        "ContinueOnError": true,
        "ContinueOnOutputTokenError": "MailchimpError",
        "EnableDebug": false
    }
}

Revised 09/25/2026