Resend
Send through the Resend API with attachments, tags, and native idempotency keys.
The Resend adapter calls the Resend Email API over fetch — no extra dependency. It is the default first adapter in these docs: short setup, broad field support, and it is the only adapter that forwards idempotency keys to the provider natively.
@opencoredev/email-sdk/resendConfigure
Grab an API key from the Resend dashboard and verify the domain you plan to send from.
import { createEmailClient } from "@opencoredev/email-sdk";
import { resend } from "@opencoredev/email-sdk/resend";
export const email = createEmailClient({
adapters: [resend({ apiKey: process.env.RESEND_API_KEY! })],
});Prop
Type
Send
Resend maps every common transactional field: cc, bcc, replyTo, headers, attachments, and tags.
const result = await email.send(
{
from: "Acme <hello@acme.com>",
to: [{ email: "user@example.com", name: "Ada" }],
replyTo: "support@example.com",
subject: "Welcome to Acme",
html: "<p>Your workspace is ready.</p>",
tags: [{ name: "type", value: "welcome" }],
attachments: [
{ filename: "welcome.txt", content: "Welcome to Acme.", contentType: "text/plain" },
],
},
{ idempotencyKey: "welcome:user_123" },
);
console.log(result.id); // Resend email id, also exposed as result.messageIdThe idempotencyKey is sent as Resend's Idempotency-Key header, so retried requests cannot double-send.
No metadata field
Resend has no metadata concept, so metadata on a message throws an EmailValidationError
before any request is made. Use tags instead, or pick a metadata-capable
adapter.
Verify from the CLI
RESEND_API_KEY="re_..." npx email-sdk doctor --adapter resendRESEND_API_KEY="re_..." npx email-sdk send \
--adapter resend \
--from "Acme <hello@acme.com>" \
--to user@example.com \
--subject "Resend smoke test" \
--text "It works" \
--dry-runDrop --dry-run to perform one real send from the environment that will send production email — that is the only check that proves the account, sender domain, and recipient policy are ready.