Migrate from the Resend SDK

Replace direct Resend calls with a typed Email SDK client while keeping Resend as the delivery adapter.

Keep your Resend API key and verified sender. The migration changes the application boundary, not the provider account.

Replace construction

before.ts

import { Resend } from "resend";
const resend = new Resend(process.env.RESEND_API_KEY);

after.ts

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

const email = createEmailClient({
  adapters: [resend({ apiKey: process.env.RESEND_API_KEY! })],
});

Replace sends

after.ts

const result = await email.send(
  {
    from: "Acme <hello@acme.com>",
    to: "user@example.com",
    subject: "Welcome",
    html: "<p>Your account is ready.</p>",
  },
  { idempotencyKey: "welcome:user_123" },
);

console.log(result.id);

Email SDK maps CC, BCC, reply-to, headers, attachments, tags, and sendAt. It rejects message metadata because the Resend adapter has no metadata mapping.

Add a backup only when compatible

A simple SMTP backup cannot carry Resend attachments, tags, or scheduling. Validate the complete route before queueing and keep onUnknownDelivery: "stop" unless you explicitly accept duplicate risk.

Verify

RESEND_API_KEY=re_xxx npx --package @opencoredev/email-sdk email-sdk doctor --adapter resend
RESEND_API_KEY=re_xxx npx --package @opencoredev/email-sdk email-sdk send \
  --adapter resend \
  --from hello@example.com \
  --to user@example.com \
  --subject "Migration smoke test" \
  --text "Dry run only." \
  --dry-run

Resend adapter

See all options and mapped fields.