EmailRep Has a Free API — Check Any Email's Reputation in One Request

#security #api #python #discuss

The Story

Last month, a friend's SaaS got flooded with fake signups. 200+ accounts from disposable emails. Their verification service cost $0.01 per check — $2 per batch, adding up fast.

Then I found EmailRep.io — a completely free API that scores any email's reputation. No API key for basic lookups. One request, instant answer.

The API

Base URL: https://emailrep.io/

curl https://emailrep.io/test@example.com

Response:

{
  "email": "test@example.com",
  "reputation": "low",
  "suspicious": true,
  "references": 0,
  "details": {
    "blacklisted": false,
    "malicious_activity": false,
    "credentials_leaked": false,
    "data_breach": false,
    "deliverable": true,
    "free_provider": false,
    "disposable": false,
    "spam": false
  }
}

Real Example: Signup Fraud Filter

import requests

def check_email_reputation(email):
    """Check if email is suspicious before allowing signup."""
    resp = requests.get(
        f"https://emailrep.io/{email}",
        headers={"User-Agent": "MyApp/1.0"}
    ).json()

    risk_score = 0
    details = resp.get("details", {})

    if details.get("disposable"):
        risk_score += 50  # Disposable email = high risk
    if details.get("spam"):
        risk_score += 30
    if resp.get("suspicious"):
        risk_score += 20
    if details.get("credentials_leaked"):
        risk_score += 10  # Compromised account

    return {
        "email": email,
        "reputation": resp.get("reputation"),
        "risk_score": risk_score,
        "allow_signup": risk_score < 40
    }

# Test it
emails = ["john@company.com", "temp@guerrillamail.com", "spam@example.com"]
for email in emails:
    result = check_email_reputation(email)
    status = "✅" if result["allow_signup"] else "🚫"
    print(f"{status} {email}: {result['reputation']} (risk: {result['risk_score']})")

Bulk Validation From CSV

import csv
import requests
import time

def validate_email_list(csv_path):
    results = []
    with open(csv_path) as f:
        reader = csv.DictReader(f)
        for row in reader:
            email = row["email"]
            resp = requests.get(
                f"https://emailrep.io/{email}",
                headers={"User-Agent": "BulkValidator/1.0"}
            ).json()
            results.append({
                "email": email,
                "reputation": resp.get("reputation", "unknown"),
                "disposable": resp.get("details", {}).get("disposable", False)
            })
            time.sleep(1)  # Be nice to the API

    clean = [r for r in results if r["reputation"] in ("high", "medium")]
    risky = [r for r in results if r["reputation"] == "low"]
    print(f"Clean: {len(clean)} | Risky: {len(risky)} | Total: {len(results)}")
    return results

Why This Is Useful

Use Case	How
Signup fraud prevention	Block disposable/suspicious emails
Email list cleaning	Remove risky addresses before campaigns
OSINT investigations	Check if email appeared in breaches
Lead validation	Score lead quality by email reputation