Kickbox API

⭐ Beginner's Pick Email / No Auth Required Beginner HTTPS CORS
Free to Use Varies (check documentation)

Overview

Kickbox provides a free, no-auth email verification endpoint that checks whether an email address is deliverable by performing syntax validation, domain MX lookup, and disposable address detection. The open endpoint at open.kickbox.com requires no API key and returns a quick binary verdict, while paid plans offer deeper SMTP verification. It is commonly used in form validation to catch bad emails at point of entry.

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Beginner Tip

Kickbox open endpoint needs no API key — just append an email address to the URL and you get an immediate JSON response. It is one of the easiest ways to add basic email validation to a signup form without any registration.

Available Data

email delivery status
message ID
bounce/complaint data
open/click tracking
Use case: Integrate email verification api data into web and mobile applications

Example Response

JSON Response
{
  "message_id": "msg_abc123def456",
  "status": "delivered",
  "to": "[email protected]",
  "subject": "Welcome!",
  "timestamp": "2025-01-15T10:30:00Z"
}

Field Reference

disposable True if the email domain is a known temporary or disposable email provider
free True if the email uses a free consumer email provider (e.g., Gmail, Yahoo, Outlook)

Implementation Example

const url = "https://open.kickbox.com/";
const response = await fetch(url);
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

Common Errors & Troubleshooting

Response shows "disposable": true for a real business email Some corporate email domains use infrastructure shared with disposable providers, triggering false positives
Use disposable as one signal alongside result — only reject if both result is undeliverable AND disposable is true
CORS error when calling from browser JavaScript The open.kickbox.com endpoint may not send CORS headers for all origins
Call the API from your server-side code and return the result to the front end, rather than making the request directly from the browser
No response or timeout for certain domains SMTP probing can time out for domains with strict firewall rules on port 25
Set a 10-second timeout and treat timeouts as unknown rather than invalid; do not block users solely on a timeout result

Matrix Score Breakdown

🌐 Reachability 30/30
⚡ Speed 15/20
🔒 Security 15/15
🛠 Developer XP 20/20
✓ Reliability 7/15
Response Time 216ms

Fully tested on Apr 5, 2026

Technical Specifications

Auth No Auth
HTTPS REQUIRED
CORS YES
Category Email
Difficulty Beginner
Verified: 2026-04-04

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