How fast is the email validation API?

BounceZero API responses for cached addresses return in under 100ms. Fresh verifications with SMTP checks typically complete in 1-3 seconds. The depth parameter lets you trade speed for depth: basic syntax+domain checks return in under 50ms.

Is there a free tier for the email validation API?

Yes. All new accounts receive 100 free verification credits — no credit card required. API access is included in all plans, starting with the free tier.

What does the API response include?

The API returns JSON with: classification (deliverable/risky/undeliverable/unknown), score (0-100), confidence, is_deliverable boolean, risk_level, domain analysis, SMTP results, catch-all status, disposable flag, role-based flag, and AI-generated explanation of the result.

Email Validation API — Real-Time Verification for Developers

Integrate in Minutes

One endpoint. Three lines of code. Works with any stack.

example.sh

# Single email verification
curl -X POST https://bouncezero.io/api/v1/verify \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"email": "user@example.com", "depth": "standard"}'

import requests

response = requests.post(
    "https://bouncezero.io/api/v1/verify",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    json={"email": "user@example.com", "depth": "standard"}
)
result = response.json()
print(result["classification"], result["score"])

const response = await fetch('https://bouncezero.io/api/v1/verify', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({ email: 'user@example.com', depth: 'standard' })
});
const { classification, score, is_deliverable } = await response.json();

$ch = curl_init('https://bouncezero.io/api/v1/verify');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer YOUR_API_KEY',
        'Content-Type: application/json'
    ],
    CURLOPT_POSTFIELDS => json_encode([
        'email' => 'user@example.com',
        'depth' => 'standard'
    ])
]);
$result = json_decode(curl_exec($ch), true);

What the API Returns

A rich JSON object with everything you need to make a reliable accept/reject decision.

response.json

{
  "email": "user@example.com",
  "classification": "deliverable",
  "score": 87.4,
  "confidence": 0.91,
  "is_deliverable": true,
  "risk_level": "low",
  "domain": {
    "mx_valid": true,
    "is_catchall": false,
    "is_disposable": false,
    "spf": true,
    "dmarc": true,
    "provider": "Google Workspace"
  },
  "smtp": {
    "connected": true,
    "mailbox_exists": true,
    "response_code": 250
  },
  "flags": {
    "is_role_based": false,
    "is_free_provider": false
  },
  "explanation": "Valid mailbox confirmed...",
  "response_time_ms": 1243
}

classification string

Result category: deliverable, risky, undeliverable, or unknown.

score float 0–100

Composite deliverability score. >75 = safe to send, 30–75 = risky, <30 = do not send.

confidence float 0–1

How confident the scoring engine is in the classification.

is_deliverable boolean

Convenience boolean: true when score ≥ 75 and classification is deliverable.

domain.is_catchall boolean

True when the domain accepts all addresses regardless of mailbox existence.

domain.is_disposable boolean

True when the domain is a known temporary or throwaway email provider.

smtp.mailbox_exists boolean

True when the SMTP server confirmed the mailbox (RCPT TO 250 OK).

explanation string

AI-generated plain English explanation of why this result was returned.

Common API Integration Use Cases

Sign-Up Form Validation

Reject invalid and disposable email addresses at the point of collection — before they enter your database and ESP contact list.

CRM Data Hygiene

Verify contacts on import or export. Flag stale addresses for re-engagement campaigns before they generate bounces.

E-commerce Checkout

Validate customer email at checkout to ensure order confirmations and receipts reach real inboxes.

Lead Generation Forms

Stop wasting ad spend on leads with invalid emails. Validate at the form level and only count real, deliverable addresses.

Data Pipelines & ETL

Enrich contact records in your data pipeline with deliverability signals. Route only valid contacts to downstream marketing tools.

Webhook & Event-Driven

Trigger email verification on HubSpot, Salesforce, or Zapier events. Automatically mark contacts as valid or invalid in your CRM.

API FAQ

How fast is the API?

Cached addresses return in under 100ms. Fresh SMTP verifications typically complete in 1–3 seconds. The depth parameter lets you control the trade-off: basic returns in <50ms (syntax + domain only), standard adds SMTP, and deep includes social signals.

Is there a free tier?

Yes. All new accounts receive 100 free verification credits with API access — no credit card required. This is enough to prototype your integration and test the full response schema before committing to a paid plan.

What are the API rate limits?

Free tier: 10 requests/minute. Starter: 60 req/min. Pro: 300 req/min. Enterprise: custom rate limits available. Rate limit headers (X-RateLimit-Remaining, X-RateLimit-Reset) are included in every response.

Does the API support bulk verification?

Yes. The POST /api/v1/verify/bulk endpoint accepts up to 1,000 addresses per request and returns an async job ID. Poll GET /api/v1/jobs/{id} for status and results. See our full documentation for the bulk API spec.

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Email Validation API: Real-Time Verification Built for Developers