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Injection vs Webhook

When to Inject a Message vs use a Webhook​

Mailinator offers a lot of solutions for automated testing, but choosing between Injecting a Message and Webhooks (Incoming) usually boils down to whether you are simulating an external sender or controlling the data flow yourself.

Webhooks:​

Webhooks are the "open door" of Mailinator. You use these when you want to receive data from a third-party service (like Stripe, GitHub, or your own app’s outbound mailer).

  • Public Access: Anyone with the URL can send data to it. No authentication is required to send the message. (Note: You do need a Webhook token)
  • The "Real World" Test: This is the best way to test how your system interacts with external services in a production-like environment.
  • Format: Typically receives standard HTTP POST requests.

Injecting a Message:​

You use the Mailinator API to manually push a message into an inbox. Learn more.

  • Secure & Private: Requires your API Key. This should only be done from your backend code or secure CI/CD environment—never from a client-side script where the key could be leaked.
  • Granular Control: Unlike a webhook, which just takes what it’s given, Injection allows you to define the sender, the subject, and the body (HTML or Text) exactly as you need it for a specific test case.
  • Speed: Since you aren't waiting on a third-party mail server to "eventually" send the email, injection is near-instantaneous for high-speed testing.
tip

We recommend using Webhooks to test if your application is correctly sending notifications. If you want to test inbox logic and don't want to wait for a real email to travel from your system to ours, inject it.