How I Built and Deployed a Free Email Validation API with Python and FastAPI

#webdev #python #beginners #productivity

I recently built and deployed my first API — an email validation
tool built with Python and FastAPI. Here's how I did it and what
I learned along the way.

Why Email Validation?

Every app that accepts user signups needs email validation.
Most developers either roll their own regex (which misses a lot)
or pay too much for an enterprise solution. I wanted to build
something simple, affordable, and reliable.

What It Does

The API checks email addresses for:

Format — RFC 5322 compliance
MX Records — confirms the domain actually receives email
Disposable domains — flags throwaway addresses like mailinator.com
Typos — catches mistakes like gmial.com and suggests gmail.com

Each response includes a 0-100 quality score.

The Tech Stack

Python — FastAPI for the web framework
dnspython — for MX record lookups
Railway — for deployment
RapidAPI — for distribution and billing

Quick Example

import requests

url = "https://email-validation52.p.rapidapi.com/validate"
params = {"email": "test@gmail.com"}
headers = {
    "X-RapidAPI-Key": "YOUR_API_KEY",
    "X-RapidAPI-Host": "email-validation52.p.rapidapi.com"
}

response = requests.get(url, headers=headers, params=params)
print(response.json())

Example Response

{
  "email": "test@gmail.com",
  "is_valid": true,
  "score": 95,
  "checks": {
    "format": true,
    "mx_record": true,
    "disposable": false,
    "typo": false
  },
  "suggestion": null,
  "elapsed_ms": 245
}

What I Learned

FastAPI is incredible for building APIs quickly. It generates
interactive documentation automatically at /docs which makes
testing and sharing your API effortless.

Deploying to Railway was surprisingly simple — connect your
GitHub repo and it handles everything else.

The hardest part wasn't the code. It was getting all the pieces
working together — deployment, billing, documentation. But once
it clicked it all made sense.