Email Validation API - Real-Time Verification | BounceZero
REST API - JSON - Sub-Second Responses

Email Validation API: Real-Time Verification Built for Developers

Integrate email verification directly into your sign-up forms, CRM pipelines, and data workflows with a single API call. BounceZero returns 65+ signal fields in JSON - including classification, score, SMTP result, catch-all status, and plain-English explanation.

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In a nutshell

An email validation API is a REST endpoint that checks an email address for deliverability in real time — returning syntax, DNS/MX, SMTP mailbox-existence, catch-all, and disposable-provider signals as JSON in sub-second responses, so developers can block bounces before they happen.

Integrate in Minutes

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

example.sh
# Single email verification
curl -X POST https://api.bouncezero.io/api/v1/verify \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"email": "[email protected]", "depth": "standard"}'

What the API Returns

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

response.json
{
  "email": "[email protected]",
  "score": 96,
  "classification": "valid",
  "is_deliverable": true,
  "risk_level": "low",
  "checks": {
    "syntax": true,
    "domain_valid": true,
    "not_disposable": true,
    "not_catch_all": true,
    "mailbox_verified": true
  },
  "metadata": {
    "internal_classification": "verified",
    "refunded": null,
    "catch_all_unresolved": null,
    "smtp_confirmed": true,
    "response_time_ms": 1243
  },
  "explanation": "Valid mailbox confirmed..."
}
classification string

Binary verdict: valid or invalid. Send to valid, suppress invalid.

score int 0-100

Confidence score. 81+ = verified, 61-80 = likely valid, 41-60 = catch-all or inconclusive, under 40 = risky or invalid.

risk_level string

low, medium (for example an unresolved catch-all) or high.

is_deliverable boolean

Convenience boolean: true when classification is valid.

metadata.internal_classification string

Detailed verdict behind the binary result: verified, likely_valid, catch_all, invalid, disposable, risky, spamtrap, unknown or error.

metadata.catch_all_unresolved boolean

True when the domain is a catch-all that could not be resolved individually (reported valid).

metadata.refunded boolean

True when the address could not be verified; it is reported invalid and the credit is refunded automatically.

checks.not_disposable boolean

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

explanation string

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?

Limits are per API key per minute and scale with your plan: 30, 100, 300 or 1,000 requests/minute. Rate limit headers (X-RateLimit-Limit, 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 10,000 addresses per request and returns an async job ID. Poll GET /api/v1/verify/bulk/{job_id}/status, then fetch /api/v1/verify/bulk/{job_id}/results. See our full documentation for the bulk API spec.

Validation at the point where leads enter

Forms and CRM imports are where most bad addresses get in. Non-freemail (business and ISP) addresses verified by BounceZero between April and October 2026 ran 14.5% invalid and 27% unknown (Lead List Quality Benchmarks 2026); real-time validation at the form keeps that share out of the pipeline before a lead record exists.

Get Your API Key

Sign up in 30 seconds, grab your API key, and make your first verification call. 100 free credits included.

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