Una alternativa a Postmark, con precios en euros.

curl -X POST https://api.outstamp.dev/v1/emails \
  -H "Authorization: Bearer $OUTSTAMP_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: welcome-42" \
  -d '{
    "from": "Acme <[email protected]>",
    "to": "[email protected]",
    "subject": "Te damos la bienvenida a Acme",
    "html": "<p>Tu cuenta está lista.</p>"
  }'

const response = await fetch("https://api.outstamp.dev/v1/emails", {
    method: "POST",
    headers: {
        Authorization: `Bearer ${process.env.OUTSTAMP_API_KEY}`,
        "Content-Type": "application/json",
        "Idempotency-Key": `welcome-${user.id}`
    },
    body: JSON.stringify({
        from: "Acme <[email protected]>",
        to: "[email protected]",
        subject: "Te damos la bienvenida a Acme",
        html: "<p>Tu cuenta está lista.</p>"
    })
});
const email = await response.json(); // 202, { id, status: queued }

import os, requests

response = requests.post(
    "https://api.outstamp.dev/v1/emails",
    headers={
        "Authorization": f"Bearer {os.environ['OUTSTAMP_API_KEY']}",
        "Idempotency-Key": f"welcome-{user.id}",
    },
    json={
        "from": "Acme <[email protected]>",
        "to": "[email protected]",
        "subject": "Te damos la bienvenida a Acme",
        "html": "<p>Tu cuenta está lista.</p>",
    },
)
email = response.json()  # 202, { id, status: queued }