How do I send transactional emails from my app using an API?

To send transactional emails from your app via an API, you generally use an email provider that exposes HTTP endpoints or an SDK. The flow is usually:

1. Choose an email service

   • Examples: SendGrid, Mailgun, Postmark, Amazon SES, Resend, MailerSend, SparkPost.
   • Pick one with good deliverability, templates, logs, and webhook support.

2. Verify your sending domain

   • Add DNS records like:
     • SPF
     • DKIM
     • often DMARC
   • This improves deliverability and helps prevent spoofing.

3. Create an API key

   • Store it securely in environment variables.
   • Never hardcode it in frontend code or public repositories.

4. Build a backend endpoint or service

   • Your app should call your backend, and your backend should call the email provider.
   • Don’t call the email API directly from the client unless the provider explicitly supports safe public usage.

5. Send the email via API

   • Typically you send:
     • to
     • from
     • subject
     • text or html
     • optional template variables

---

Example: generic API request

curl -X POST https://api.emailprovider.com/v1/send \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "Your App <no-reply@yourdomain.com>",
    "to": "user@example.com",
    "subject": "Welcome!",
    "html": "<h1>Thanks for signing up</h1><p>We’re glad to have you.</p>"
  }'

---

Example: Node.js using a provider SDK

import provider from "email-provider-sdk";

provider.setApiKey(process.env.EMAIL_API_KEY);

await provider.send({
  from: "Your App <no-reply@yourdomain.com>",
  to: "user@example.com",
  subject: "Password reset",
  html: "<p>Click here to reset your password.</p>"
});

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Typical transactional email use cases

• Welcome email
• Email verification
• Password reset
• Purchase receipt
• Order/shipping updates
• Security alerts

---

Best practices

• Use a no-reply or dedicated sending address.
• Keep content short and relevant.
• Use templates with variables for consistency.
• Add unsubscribe only if the email is promotional; transactional emails usually don’t require it.
• Set up webhooks for delivery, bounce, and complaint events.
• Retry transient failures, but avoid duplicate sends.
• Log message IDs so you can trace sends later.

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Recommended architecture

Frontend → your backend → email API provider

That way you can:

• protect credentials
• validate inputs
• rate-limit requests
• prevent abuse

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If you want, I can show you:

• a complete example in Node.js / Python / PHP / Go
• how to send templated emails
• how to set up SPF/DKIM/DMARC
• or how to do this with a specific provider like SendGrid, SES, Postmark, or Resend