SMTPSeer
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See the signal behind every address.

Run every check, from syntax to SMTP, in one fast, traceable workflow.

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Syntax
Disposable
DNS
SMTP
Valid

[email protected]

  • SyntaxPassed
  • DisposablePassed
  • DNSPassed
  • SMTPPassed
Explore

Four layers. One reliable result.

Each email address passes through four checks to reach a reliable result.

Syntax

Format and standards checks

Disposable

Disposable address detection

DNS

Domain and record verification

SMTP

Real-time server checks

Reliable resultAll signals in one workflow

From one address to millions.

Verify one address or process millions of emails. SMTPSeer is built for your operational needs.

Instant verification

Verify a single address in seconds.

Bulk CSV processing

Process large lists in the background.

Retry queue

Automatically retry temporary failures.

Caching

Get faster results for repeated queries.

Catch-all detection

Identify uncertain and risky domains.

Proxy routing

Route checks through secure paths when needed.

Detailed activity logs

Track and audit every action in one place.

Clear results. Honest uncertainty.
  • valid
  • invalid
  • hard bounce
  • soft bounce
  • catch-all
  • unknown

Built for developers.

Integrate SMTPSeer directly into your systems with a simple, powerful, and flexible API.

API keys

Separate, scoped access for each environment.

Bulk verification endpoints

Process large lists efficiently.

Idempotent requests

Safe, repeatable operations.

Webhook notifications

Deliver results to your systems as they arrive.

curl -X POST https://api.smtpseer.com/validate \
  -H "x-app-id: your-app" \
  -H "x-api-key: smtpseer_••••••••" \
  -H "Content-Type: application/json" \
  -d '{"email":"[email protected]"}'
200 OK 
{
  "email": "[email protected]",
  "status": "valid",
  "checks": {
    "syntax": "pass",
    "disposable": "pass",
    "dns": "pass",
    "smtp": "pass"
  }
}

Security is at our core.

Layers of protection safeguard your data and operations.

Account-specific keys

Access stays isolated and controlled.

Protected sessions

Secure, time-limited access.

Rate limits

Fair, reliable access.

Auditable activity

Every action is recorded.

Clean your lists.
Keep the signal.

Cleaner lists. Healthier operations. Get started today.

Get started