Mailchimp API

Send Mailchimp campaigns via RelayAPI — create and send email campaigns alongside social media posts in a single API call.

Quick Reference

Property	Value
Platform key	`mailchimp`
Auth method	API Key (includes datacenter)
Content format	HTML (plain text auto-wrapped)
Scheduling	Yes
Analytics	No

Before You Start

You need a Mailchimp API key. Get one from Mailchimp Account > Extras > API Keys. The key includes your datacenter suffix (e.g., abc123def-us21).

You also need at least one audience/list in your Mailchimp account, and a valid from_email address.

Connect

curl -X POST https://api.relayapi.dev/v1/connect/mailchimp \
  -H "Authorization: Bearer $RELAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "api_key": "your-mailchimp-api-key-us21"
  }'

Send a Campaign

curl -X POST https://api.relayapi.dev/v1/posts \
  -H "Authorization: Bearer $RELAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "content": "Our latest newsletter...",
    "targets": ["twitter", "acc_mailchimp123"],
    "scheduled_at": "now",
    "target_options": {
      "mailchimp": {
        "subject": "Monthly Update",
        "preview_text": "What happened this month",
        "from_email": "hello@example.com",
        "from_name": "Your Company",
        "list_id": "abc123"
      }
    }
  }'

`target_options` Fields

Field	Type	Required	Description
`subject`	string	No	Email subject line. Falls back to first line of content.
`preview_text`	string	No	Preview text for email clients.
`from_email`	string	Yes	Sender email address.
`from_name`	string	No	Sender display name.
`list_id`	string	No	Audience/list ID. If omitted, uses the first list in your account.
`content_html`	string	No	Full HTML body. If omitted, plain text is auto-wrapped.

Discovery

List audiences and templates:

GET /v1/accounts/{id}/lists      # Returns Mailchimp audiences
GET /v1/accounts/{id}/templates  # Returns Mailchimp templates

Automations

Mailchimp uses data-center-scoped URLs ({dc}.api.mailchimp.com/3.0). The data center is auto-detected from the API key suffix (-us14) or from metadata.dc.

Triggers

Type	Fires on
`mailchimp_subscribe`	New subscribe event (webhook)
`mailchimp_unsubscribe`	Unsubscribe event

Mailchimp webhooks are form-encoded (not JSON). The inbox normalizer needs a form-parser branch when wiring this platform's webhook route.

Send nodes

Subscriber operations require the MD5 hash of the lowercased email as the identifier.

Node	Endpoint	Required fields
`mailchimp_add_member`	`PUT /lists/{list}/members/{hash}` (upsert)	`email`, optional `double_optin` / `merge_fields`
`mailchimp_add_tag`	`POST /lists/{list}/members/{hash}/tags`	`email`, `tag`
`mailchimp_send_campaign`	`POST /campaigns/{id}/actions/send`	`campaign_id`

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Mailchimp API

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