Nodemailer

npm install nodemailer

mail.ts

import nodemailer from "nodemailer";

export const transport = nodemailer.createTransport({
  host: "smtp.spacepost.dev",
  port: 25976,
  secure: false, // STARTTLS: the connection is upgraded to TLS before login
  requireTLS: true,
  auth: { user: "spacepost", pass: process.env.SPACEPOST_API_KEY },
});

await transport.sendMail({
  from: '"Acme" <hello@acme.com>',
  to: ["user@example.com"],
  cc: "manager@example.com",
  subject: "Your invoice",
  text: "Invoice attached.",
  html: '<p>Invoice attached.</p><img src="cid:logo" />',
  attachments: [
    { filename: "invoice.pdf", path: "./invoice.pdf" },
    { filename: "logo.png", path: "./logo.png", cid: "logo" },
  ],
  headers: {
    "X-SpacePost-Tags": "category=invoice, order_id=1042",
    "X-SpacePost-Scheduled-At": "in 1 hour",
  },
});

Usa un pool de conexiones para volúmenes altos:

nodemailer.createTransport({
  host: "smtp.spacepost.dev",
  port: 25976,
  secure: false,
  requireTLS: true,
  pool: true,
  maxConnections: 5,
  auth: { user: "spacepost", pass: process.env.SPACEPOST_API_KEY },
});

secure: false con requireTLS: true significa STARTTLS: Nodemailer se conecta en texto plano y pasa a TLS antes de enviar tu clave de API, y se niega a continuar si la actualización falla. Todavía no se ofrece TLS implícito (secure: true, puerto 465).

Para código nuevo, prefiere el SDK de Node.js: devuelve el id del correo y errores más detallados.