Next.js

Send email from a route handler or a server action. Both run on your server, so your API key stays out of the browser.

npm install wakio

Set WAKIO_API_KEY in .env.local and in your host's environment settings. You can create the client at the top of a module: it reads the key when it first sends, so next build works without it.

In a route handler

// app/api/welcome/route.ts
import { Wakio } from "wakio"
import { auth } from "@/auth"

const wakio = new Wakio()

export async function POST() {
  const session = await auth()
  if (!session?.user?.email) return new Response(null, { status: 401 })

  await wakio.emails.send({ to: session.user.email, subject: "Welcome to Acme", html: "<p>Thanks for signing up.</p>" })
  return Response.json({ ok: true })
}

The route sends only to the signed-in user's own address. A public route that emails an address from the request would let anyone send mail through your account.

In a server action, with React Email

// app/actions.tsx
"use server"

import { render } from "@react-email/render"
import { Wakio } from "wakio"
import { auth } from "@/auth"
import { WelcomeEmail } from "@/emails/welcome"

const wakio = new Wakio({ render })

export async function sendWelcome() {
  const session = await auth()
  if (!session?.user?.email) throw new Error("Not signed in")

  await wakio.emails.send({
    to: session.user.email,
    subject: "Welcome to Acme",
    react: <WelcomeEmail name={session.user.name ?? "there"} />,
  })
}

The package also runs on the Edge runtime.

For the full client, see Node.js.