Send email from Remix using `nodemailer`

email.server.tsx

import type { Transporter } from 'nodemailer'
import nodemailer from 'nodemailer'
import Mail from 'nodemailer/lib/mailer'
declare global {
  var transport: Transporter
}
const transporter: Transporter =
  global.transport ?? (global.transport = getTransport())

function getTransport() {
  const transporter = nodemailer.createTransport({
    pool: true,
    host: process.env.SMTP_HOST,
    port: Number(process.env.SMTP_PORT),
    secure: true,
    auth: {
      user: process.env.SMTP_USERNAME,
      pass: process.env.SMTP_PASSWORD,
    },
    tls: {
      ciphers: 'SSLv3',
      rejectUnauthorized: false,
    },
  })
  return transporter
}

export async function sendMail(mailOptions: Mail.Options) {
  return transporter.sendMail(mailOptions)
}

forgot-password.tsx

// routes/forgot-password.tsx
export const action = async ({ request }: ActionArgs) => {
  const formData = await request.formData()
  const email = String(formData.get('email'))
  const user = await getUserByEmail(email)

  if (!user) {
    // say it's sent even if we don't have a user to prevent harvesting
    return redirect('/forgot-password/sent')
  }

  user.resetToken = getResetToken()
  // token expires in 3 days
  user.resetTokenExpires = new Date(Date.now() + 1000 * 60 * 60 * 24 * 3)
  await updateUser(user)

  const url = new URL(`${process.env.SERVER_URL}/reset-password`)
  url.searchParams.set('email', email)
  url.searchParams.set('token', user.resetToken)
  const link = url.toString()

  const html = renderToString(
    <EmailTemplate
      url={process.env.SERVER_URL}
      email={email}
      link={link}
    />,
  )
  const result = await sendMail({
    from: process.env.EMAIL_SENDER,
    to: email,
    subject: 'Password Reset',
    html,
  })
  return redirect('/forgot-password/sent')
}