Mailchimp Transactional

Send through Mailchimp Transactional (Mandrill) with typed recipients, tags, and metadata, but no replyTo field.

Capabilities

Repeated headers	Idempotency	Scheduling	Personalized
No	`none`	Yes	`expanded`

These values come from the adapter's exported capabilities declaration. The field support matrix covers normalized message fields.

The Mailchimp adapter calls the Mailchimp Transactional API, the API formerly known as Mandrill, with plain fetch. Unusually, the API key travels in the request body rather than a header, and recipients are a single typed list (to/cc/bcc entries) instead of separate arrays.

Mailchimp Transactional@opencoredev/email-sdk/mailchimp

Provider docs

Configure

Create a Transactional API key in the Mandrill dashboard (Settings → SMTP & API Info) and verify your sending domain.

lib/email.ts

import { createEmailClient } from "@opencoredev/email-sdk";
import { mailchimp } from "@opencoredev/email-sdk/mailchimp";

export const email = createEmailClient({
  adapters: [mailchimp({ apiKey: process.env.MAILCHIMP_API_KEY! })],
});

Prop

Type

Send

Mailchimp maps cc, bcc, headers, attachments, tags (values only), and metadata. sendAt maps to Mailchimp's send_at (a UTC timestamp), and Mailchimp only schedules email for accounts with a positive balance.

const result = await email.send({
  from: "Acme <hello@acme.com>",
  to: [{ email: "user@example.com", name: "Ada" }],
  subject: "Your order has shipped",
  html: "<p>Order ord_123 is on its way.</p>",
  metadata: { orderId: "ord_123" },
  tags: [{ name: "type", value: "shipping" }],
});

console.log(result.id); // Mandrill _id of the first recipient result

Mandrill responds with one result per recipient; the normalized id comes from the first result's _id. Each result also carries a per-recipient status (sent, queued, rejected). If a send succeeds but mail does not arrive, check result.raw during smoke tests, because a rejected status still counts as a successful API call.

No replyTo field

This adapter does not support replyTo; setting it throws an EmailValidationError before any request is made. Set a Reply-To header instead: headers: [{ name: "Reply-To", value: "support@acme.com" }]. See field support for the full matrix.

Verify from the CLI

MAILCHIMP_API_KEY="md-..." npx --package @opencoredev/email-sdk email-sdk doctor --adapter mailchimp

MAILCHIMP_API_KEY="md-..." npx --package @opencoredev/email-sdk email-sdk send \
  --adapter mailchimp \
  --from "Acme <hello@acme.com>" \
  --to user@example.com \
  --subject "Mailchimp smoke test" \
  --text "It works" \
  --dry-run

Drop --dry-run for one real send and check the per-recipient status in the output; Mandrill can accept the request and still reject the recipient.

Frequently asked questions

Does Email SDK support Mailchimp Transactional?

Yes. Email SDK ships a Mailchimp Transactional adapter imported from @opencoredev/email-sdk/mailchimp. You keep your Mailchimp Transactional account and credentials; the SDK adds message validation, typed errors, and no-network test adapters around the same send() call used for every other provider.

Which message fields does the Mailchimp Transactional adapter support?

Mailchimp Transactional supports CC recipients, BCC recipients, Custom headers, Attachments, Tags, Metadata, and Scheduled sending (sendAt). It does not support Reply-To address; Email SDK rejects a message that uses those fields before any request is made.

Can Mailchimp Transactional schedule email for later with Email SDK?

Yes. Set sendAt on the message and the Mailchimp Transactional adapter passes the scheduled time to the provider.

Does the Mailchimp Transactional adapter support idempotent sends?

No. Mailchimp Transactional has no provider-side idempotency, so a retried send can be delivered twice. Deduplicate in your own queue before retrying.