# Sending modes (/docs/concepts/sending-modes)



Email SDK separates independent messages from one message personalized across recipients.

## Independent sends [#independent-sends]

Use `sendMany` when every item is a complete message with its own outcome. Execution is sequential and preserves input order.

```ts title="src/send-notifications.ts"
const results = await email.sendMany([
  { message: welcomeMessage, options: { idempotencyKey: "welcome:1" } },
  { message: receiptMessage, options: { idempotencyKey: "receipt:1" } },
]);
```

The method returns one settled result per item. Item options override method-level options, including replacement of the fallback object.

## Personalized recipients [#personalized-recipients]

Use `sendPersonalized` when subject or body tokens vary by recipient.

```ts title="src/send-campaign.ts"
const result = await email.sendPersonalized(
  {
    message: {
      from: "Acme <hello@acme.com>",
      subject: "Hi %recipient.name%",
      text: "Welcome, %recipient.name%.",
    },
    recipients: [
      { to: "ada@example.com", variables: { name: "Ada" } },
      { to: "linus@example.com", variables: { name: "Linus" } },
    ],
  },
  { idempotencyKey: "campaign:42" },
);
```

Mailgun and SendGrid use native personalized APIs. Other built-in adapters expand recipients into deterministic sequential sends. At least one accepted recipient resolves with `accepted` and `rejected`; zero accepted recipients throws `EmailAllRecipientsFailedError`.

## Scheduled sends [#scheduled-sends]

`sendAt` accepts a `Date` or RFC 3339 string with `Z` or a numeric offset.

```ts title="src/send-later.ts"
await email.send({
  ...message,
  sendAt: "2026-08-01T09:00:00Z",
});
```

The SDK does not wait or queue. Capable adapters translate the timestamp into the provider's scheduling field. Incapable adapters reject it during validation.

## Idempotency [#idempotency]

Pass `idempotencyKey` in send options, not in `EmailMessage`.

```ts title="src/send-receipt.ts"
await email.send(receipt, {
  idempotencyKey: "receipt:order_123",
});
```

Resend, JetEmail, Lettermint, and Primitive have native idempotency support. SMTP derives `Message-ID` from the key. Other adapters receive the key in context but cannot guarantee provider-side deduplication.

<Card title="Message reference" href="/docs/reference/message" description="See exact message, attachment, header, and schedule types." />

<Card title="Capability groups" href="/docs/adapters/capability-groups" description="Choose adapters that support the sending mode you need." />