EU-hosted email API for transactional and marketing email, with contacts, broadcasts, and analytics
This API requires an API key for authentication. Here's how to get started:
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?api_key=YOUR_KEY) or in the request header (Authorization: Bearer YOUR_KEY). Check the API's documentation for the exact format.API keys are free for most public APIs. They're used to identify your application and enforce rate limits — not to charge you.
This API does not support CORS, so you'll need to call it from a server-side application or use a proxy. Direct browser requests will be blocked by the browser's same-origin policy.
PostStack is a free API in the Email category. It requires a free API key, which you can obtain by signing up on their website. This API supports HTTPS for secure connections and does not support CORS — you will need to call it from a server-side application.
PostStack fits naturally into projects that touch the Email space. Here are a few directions developers commonly take when working with APIs in this category — any of them could be a fit depending on the specific endpoints PostStack exposes:
If a specific use case isn't listed, scroll back to the code examples above and adapt the request shape to match the endpoint you need. Most Email APIs follow similar request/response patterns, so the snippet that works for one endpoint usually works for the rest with small tweaks.
1. Skim the documentation first. Open the link above and look for two things: the base URL pattern and a list of available endpoints. Knowing both up front saves you from guessing parameter names or formats. Most providers also publish example responses next to each endpoint — copy one into your editor as a reference for the JSON shape your code will be parsing.
2. Get an API key. PostStack uses API key authentication. Sign up on the provider's site, look for a developer dashboard or API section in your account settings, and copy your key somewhere safe. Treat it like a password — don't paste it into a public repo or a client-side bundle that ships to a browser. Read our API security guide if you're unsure how to keep keys out of source control.
3. Make a request from the command line. Before wiring an API into your application, send a single request with curl or your HTTP client of choice. Confirm that the response shape matches what the docs promised. If it doesn't, your application code would have hit the same surprise — better to find out now while you only have one terminal window to debug.
4. Wire it into your code. Once a manual request works, copy that request into your application as a function. Add error handling: APIs return 4xx and 5xx codes for client and server errors respectively, and your code needs to behave reasonably when one comes back. Our error-handling guide covers the patterns that make this less painful.
5. Don't call it directly from the browser. PostStack doesn't support CORS, so a browser-side fetch() will be blocked by the same-origin policy. Call it from your backend instead and forward the result to the frontend. If you don't have a backend, a serverless function (Cloudflare Workers, Netlify Functions, Vercel) is a quick way to add one.
Authorization header, or a custom header — every provider does it slightly differently. The official docs will say which.curl but not in your app: almost always a header-encoding bug. Print the exact request your client sends and compare it to your working curl command. Look for missing quotes, extra spaces, or a header name typo.Email APIs let you send transactional emails, verify addresses, and manage mailing lists. Handle email delivery, validation, and inbox management without running your own mail servers.
PostStack is one of dozens of free Email APIs we've catalogued. Some are nearly interchangeable; others have distinct strengths and weaknesses that only become clear when you read their docs side-by-side. If PostStack doesn't quite fit your project, the Email category page lists every alternative we know about, with auth and CORS columns so you can compare at a glance.
When evaluating Email APIs, the criteria that matter most are typically: rate limits on the free tier, freshness of the underlying data, regional coverage (does it work for your users' geography?), and how active the provider's maintenance schedule is. APIs that haven't been updated in years tend to drift out of sync with the underlying data sources, even if they technically still respond.
PostStack is an API in the Email category. The specific data it returns depends on its endpoints — this could include structured records, search results, media files, or computed values. Visit the official documentation for a complete list of endpoints and response schemas.
As a Email API, PostStack can be integrated into web apps, mobile apps, browser extensions, chatbots, data dashboards, or backend services. Common use cases include displaying live data on a website, automating data collection, building comparison tools, or enriching your own database with external information.
Yes — browse our Email category to see all available APIs in the same space. Using multiple APIs can help with redundancy (if one goes down) and provide richer data by combining different sources.
Yes, PostStack is listed as a free public API. You will need to create a free account to get an API key, but the key itself is free. Some APIs have rate limits on their free tier, so check the official documentation for current limits.
We have not recently verified the status of PostStack. Try visiting the API URL directly or making a test request to check if it is currently online.