Remix and React Router

npm install @emails.sh/sdk

# .env, read by the dev server. The key comes from
# https://emails.sh/dashboard/api-keys.
EMAILSSH_API_KEY=esh_your_key_here

// app/routes/subscribe.tsx
import { Form, useActionData } from '@remix-run/react';
import { json, type ActionFunctionArgs } from '@remix-run/node';
import { Emailssh } from '@emails.sh/sdk';

export async function action({ request }: ActionFunctionArgs) {
  const form = await request.formData();
  const address = String(form.get('email') ?? '');
  if (!address.includes('@')) return json({ message: 'Enter an email address.' }, { status: 400 });

  const mail = new Emailssh({ apiKey: process.env.EMAILSSH_API_KEY });

  try {
    const { id } = await mail.send({
      from: 'Acme <hello@acme.com>',
      to: [address],
      subject: 'Confirm your subscription',
      html: '<p>Click the link in this email to confirm.</p>',
      idempotencyKey: `subscribe-${address}`
    });
    return json({ id });
  } catch (err) {
    console.error('emails.sh refused the send', err);
    return json({ message: 'Could not send that email.' }, { status: 502 });
  }
}

export default function Subscribe() {
  const data = useActionData<typeof action>();

  return (
    <Form method="post">
      <label htmlFor="email">Email</label>
      <input id="email" name="email" type="email" required />
      <button type="submit">Subscribe</button>
      {data && 'message' in data ? <p>{data.message}</p> : null}
      {data && 'id' in data ? <p>Check your inbox.</p> : null}
    </Form>
  );
}