# Send a batch

> Part of the Cowliss docs. Markdown for every page: append `index.md` to its URL. Site map: /llms.txt

```ts
const { data } = await resend.batch.send([
  { to: ["ada@acme-demo.io"], subject: "Your receipt", html: "<p>Thanks.</p>" },
  { to: ["grace@acme-demo.io"], template: { id: "vip-order", variables: { orderId: "A-2292" } } },
]);

data?.data; // [{ id: "dlv_…" }, { id: "dlv_…" }], in the order you sent them
```

Every message is checked before any of them is handed over, so a list with a mistake anywhere sends nothing and the answer names the message it means.

`Idempotency-Key` is honoured on a [single send](/resend/send/), where a repeat of the same key replays the first successful answer. It is **ignored on a batch**: retry one and you have sent it twice.