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Mailtrap Email Integration

Guides agents through integrating transactional email sending via Mailtrap's Email API, including sandbox testing, domain verification, and API authentication. Use when implementing email-sending features, debugging delivery issues, or setting up safe dev/staging email testing.

affaan-m on GitHub

Curated by PromptsEdge from a public repo · MIT license. All credit goes to the author.

What is this skill?

Patterns for adding transactional email sending to an application using Mailtrap's Email API and Sandbox, covering authentication, environment separation, and common delivery pitfalls.

When to use

  • Implementing a "send email" feature (signup confirmation, password reset, notifications, receipts)
  • Debugging why emails aren't arriving in dev/staging
  • Setting up a project's first email-sending integration
  • Reviewing code that calls an email API directly without sandbox separation

Core Concepts

Sandbox vs. Production separation. Mailtrap provides a Sandbox API that captures emails without delivering them, used for dev/staging so test emails never reach real inboxes. Production sending uses a separate, verified-domain endpoint. Never point a dev environment at the production sending endpoint.

Authentication. Requests use a Bearer token in the Authorization header. Tokens are scoped per project; sandbox and production typically use different tokens.

Domain verification. Production sending requires verifying a sending domain via DNS records (SPF, DKIM, DMARC) before Mailtrap will deliver to real recipients. Skipping this causes silent delivery failures or spam-folder placement.

Code Examples

typescript
// Sending via Mailtrap's Email API (production)
async function sendEmail(to: string, subject: string, html: string) {
  const response = await fetch("https://send.api.mailtrap.io/api/send", {
    method: "POST",
    headers: {
      "Authorization": `Bearer ${process.env.MAILTRAP_API_TOKEN}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      from: { email: "[email protected]", name: "Your App" },
      to: [{ email: to }],
      subject,
      html,
    }),
  });

  if (!response.ok) {
    throw new Error(`Email send failed: ${response.status}`);
  }
  return response.json();
}
typescript
// Same call, routed to Sandbox in non-production environments
const MAILTRAP_ENDPOINT = process.env.NODE_ENV === "production"
  ? "https://send.api.mailtrap.io/api/send"
  : `https://sandbox.api.mailtrap.io/api/send/${process.env.MAILTRAP_INBOX_ID}`;

Anti-Patterns

Anti-PatternWhy It's a ProblemInstead
Using the production sending endpoint in dev/testReal test emails reach real inboxes, risking spam complaints and leaked test dataRoute non-production environments to the Sandbox endpoint
Hardcoding API tokens in sourceCredential leak risk if committed to version controlLoad tokens from environment variables / secrets manager
Sending before domain verification completesEmails silently fail or land in spamVerify SPF/DKIM/DMARC records before enabling production sending
No retry/error handling on send failuresSilent notification failures (e.g., user never gets password reset email)Check response status, log failures, surface actionable errors

Best Practices

  • Keep sandbox and production tokens in separate environment variables, never share one token across environments
  • Verify sending domain DNS records before any production launch involving email
  • Log delivery failures with enough context to debug (recipient, template, timestamp, response code)
  • Treat email sending as a fallible network call: wrap in try/catch, never assume success

Related Skills

api-and-interface-design, security-and-hardening, ci-cd-and-automation

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