email

# Email Integration (Resend + React Email) You are an expert in sending emails from Vercel-deployed applications — covering Resend (native Vercel Marketplace integration), React Email templates, domain verification, and transactional email patterns. ## Vercel Marketplace Setup (Recommended) Resend is a native Vercel Marketplace integration with auto-provisioned API keys and unified billing. ### Install via Marketplace ```bash # Install Resend from Vercel Marketplace (auto-provisions env vars) vercel integration add resend ``` Auto-provisioned environment variables: - `RESEND_API_KEY` — server-side API key for sending emails ### SDK Setup ```bash # Install the Resend SDK npm install resend # Install React Email for building templates npm install react-email @react-email/components ``` ### Initialize the Client Current Resend SDK version: **6.9.x** (actively maintained, weekly downloads ~1.6M). ```ts // lib/resend.ts import { Resend } from "resend"; export const resend = new Resend(process.env.RESEND_API_KEY); ``` ## Sending Emails ### Basic API Route ```ts // app/api/send/route.ts import { NextResponse } from "next/server"; import { resend } from "@/lib/resend"; export async function POST(req: Request) { const { to, subject, html } = await req.json(); const { data, error } = await resend.emails.send({ from: "Your App <hello@yourdomain.com>", to, subject, html, }); if (error) { return NextResponse.json({ error }, { status: 400 }); } return NextResponse.json({ id: data?.id }); } ``` ### Send with React Email Template ```ts // app/api/send/route.ts import { NextResponse } from "next/server"; import { resend } from "@/lib/resend"; import WelcomeEmail from "@/emails/welcome"; export async function POST(req: Request) { const { name, email } = await req.json(); const { data, error } = await resend.emails.send({ from: "Your App <hello@yourdomain.com>", to: email, subject: "Welcome!", react: WelcomeEmail({ name }), }); if (error) { return NextResponse.json({ error }, { status: 400 }); } return NextResponse.json({ id: data?.id }); } ``` ## React Email Templates ### Template Structure Organize templates in an `emails/` directory at the project root: ``` emails/ welcome.tsx invoice.tsx reset-password.tsx ``` ### Example Template ```tsx // emails/welcome.tsx import { Body, Container, Head, Heading, Html, Link, Preview, Text, } from "@react-email/components"; interface WelcomeEmailProps { name: string; } export default function WelcomeEmail({ name }: WelcomeEmailProps) { return ( <Html> <Head /> <Preview>Welcome to our platform</Preview> <Body style={{ fontFamily: "sans-serif", backgroundColor: "#f6f9fc" }}> <Container style={{ padding: "40px 20px", maxWidth: "560px" }}> <Heading>Welcome, {name}!</Heading> <Text> Thanks for signing up. Get started by visiting your{" "} <Link href="https://yourdomain.com/dashboard">dashboard</Link>. </Text> </Container> </Body> </Html> ); } ``` ### Preview Templates Locally ```bash # Start the React Email dev server to preview templates npx react-email dev ``` This opens a browser preview at `http://localhost:3000` where you can view and iterate on email templates with hot reload. ### Upload Templates to Resend (React Email 5.0) ```bash # Upload templates directly from the CLI npx react-email@latest resend setup ``` Paste your API key when prompted — templates are uploaded and available in the Resend dashboard. ### Dark Mode Support (React Email 5.x) React Email 5.x (latest 5.2.9, `@react-email/components` 1.0.8) supports dark mode with a theming system tested across popular email clients. Now also supports **React 19.2** and **Next.js 16**. Use the `Tailwind` component with Tailwind CSS v4 for email styling: ```tsx import { Tailwind } from "@react-email/components"; export default function MyEmail() { return ( <Tailwind> <div className="bg-white dark:bg-gray-900 text-black dark:text-white"> <h1>Hello</h1> </div> </Tailwind> ); } ``` **Upgrade note (v4 → v5)**: Replace all `renderAsync` with `render`. The Tailwind component now only supports Tailwind CSS v4. ## Domain Verification To send from a custom domain (not `onboarding@resend.dev`), verify your domain in Resend: 1. Go to [Resend Domains](https://resend.com/domains) 2. Add your domain 3. Add the DNS records (MX, SPF, DKIM) to your domain provider 4. Wait for verification (usually under 5 minutes) Until your domain is verified, use `onboarding@resend.dev` as the `from` address for testing. ## Common Patterns ### Batch Sending ```ts const { data, error } = await resend.batch.send([ { from: "hello@yourdomain.com", to: "user1@example.com", subject: "Update", html: "<p>Content for user 1</p>", }, { from: "hello@yourdomain.com", to: "user2@example.com", subject: "Update", html: "<p>Content for user 2</p>", }, ]); ``` ### Server Action ```ts "use server"; import { resend } from "@/lib/resend"; import WelcomeEmail from "@/emails/welcome"; export async function sendWelcomeEmail(name: string, email: string) { const { error } = await resend.emails.send({ from: "Your App <hello@yourdomain.com>", to: email, subject: "Welcome!", react: WelcomeEmail({ name }), }); if (error) throw new Error("Failed to send email"); } ``` ### Broadcast API (February 2026) Send emails to audiences (mailing lists) managed in Resend: ```ts // Send a broadcast to an audience const { data, error } = await resend.broadcasts.send({ audienceId: "aud_1234", from: "updates@yourdomain.com", subject: "Monthly Newsletter", react: NewsletterEmail({ month: "March" }), }); // Create and manage broadcasts programmatically const broadcast = await resend.broadcasts.create({ audienceId: "aud_1234", from: "updates@yourdomain.com", subject: "Product Update", react: ProductUpdateEmail(), }); // Schedule for later await resend.broadcasts.send({ broadcastId: broadcast.data?.id, scheduledAt: "2026-03-15T09:00:00Z", }); ``` ### Idempotency Keys Prevent duplicate sends on retries by passing an `Idempotency-Key` header: ```ts const { data, error } = await resend.emails.send( { from: "hello@yourdomain.com", to: "user@example.com", subject: "Order Confirmation", react: OrderConfirmation({ orderId: "ord_123" }), }, { headers: { "Idempotency-Key": `order-confirmation-ord_123`, }, } ); ``` Resend deduplicates requests with the same idempotency key within a 24-hour window. Use deterministic keys derived from your business logic (e.g., `order-confirmation-${orderId}`). ### Webhook Management API Create and manage webhooks programmatically instead of through the dashboard: ```ts // Create a webhook endpoint const { data } = await resend.webhooks.create({ url: "https://yourdomain.com/api/webhook/resend", events: ["email.delivered", "email.bounced", "email.complained", "email.suppressed"], }); // List all webhooks const webhooks = await resend.webhooks.list(); // Delete a webhook await resend.webhooks.remove(webhookId); ``` ### Email Status: "suppressed" Resend now tracks a `"suppressed"` delivery status for recipients on suppression lists (previous hard bounces or spam complaints). Check for this in webhook events alongside delivered/bounced/complained. ### Webhook for Delivery Events ```ts // app/api/webhook/resend/route.ts import { NextResponse } from "next/server"; export async function POST(req: Request) { const event = await req.json(); switch (event.type) { case "email.delivered": // Track successful delivery break; case "email.bounced": // Handle bounce — remove from mailing list break; case "email.complained": // Handle spam complaint — unsubscribe user break; } return NextResponse.json({ received: true }); } ``` ## Environment Variables | Variable | Scope | Description | |----------|-------|-------------| | `RESEND_API_KEY` | Server | Resend API key (starts with `re_`) | ## Cross-References - **Marketplace install and env var provisioning** → `⤳ skill: marketplace` - **API route patterns** → `⤳ skill: routing-middleware` - **Environment variable management** → `⤳ skill: env-vars` - **Serverless function config** → `⤳ skill: vercel-functions` ## Official Documentation - [Resend + Vercel Marketplace](https://vercel.com/marketplace/resend) - [Resend Documentation](https://resend.com/docs) - [Resend Next.js Quickstart](https://resend.com/docs/send-with-nextjs) - [React Email Documentation](https://react.email/docs/introduction) - [React Email Components](https://react.email/docs/components/html)