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Why Validate Emails?

Email validation helps you:
  • Reduce bounce rates by up to 98%
  • Protect your sender reputation from hard bounces
  • Save money by not sending to invalid addresses
  • Improve deliverability by maintaining a clean list

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Validating a Single Email

Use the validation API to check if an email address is valid before sending. 
curl -X POST https://api.unosend.co/validation/verify \
  -H "Authorization: Bearer un_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "user@example.com"
  }'

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Response

response.json
{
  "email": "user@example.com",
  "valid": true,
  "confidence": "high",
  "checks": {
    "syntax": true,
    "mx": true,
    "mailbox": true,
    "disposable": false,
    "role": false,
    "free": true
  },
  "suggestion": null
}

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Validation Checks

Each validation performs multiple checks:
CheckDescription
SyntaxRFC-compliant email format validation
MX RecordsVerify domain has valid mail servers
MailboxSMTP-level check if mailbox exists
DisposableDetect temporary email services
RoleFlag role-based addresses (info@, support@)
FreeIdentify free email providers (gmail, yahoo)

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Confidence Levels

The API returns a confidence level for each validation:
ConfidenceDescriptionRecommended Action
highEmail is definitely validSafe to send
mediumEmail might be validSend with caution
lowEmail is likely invalidDo not send

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Validate at Signup

The best time to validate is at the point of capture. Here’s an example signup form: 
async function handleSignup(email) {
  // Validate email first
  const validation = await fetch('https://api.unosend.co/validation/verify', {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer un_your_api_key',
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ email })
  }).then(r => r.json());

  if (!validation.valid) {
    if (validation.suggestion) {
      return { error: `Did you mean ${validation.suggestion}?` };
    }
    return { error: 'Please enter a valid email address' };
  }

  if (validation.checks.disposable) {
    return { error: 'Please use a non-disposable email address' };
  }

  // Proceed with signup
  await createUser(email);
}

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Bulk Validation

Validate thousands of emails at once by uploading a CSV file in the dashboard, or use the bulk API: 
curl -X POST https://api.unosend.co/validation/list \
  -H "Authorization: Bearer un_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "emails": [
      "user1@example.com",
      "user2@example.com",
      "invalid@nonexistent.xyz"
    ]
  }'
Bulk validation is available on Pro plan only. Free plan users should use the single email validation endpoint.

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Pricing

PlanCreditsPrice
Free1,000 credits$0/forever
Pro100,000 credits/month$29/month
Each validation uses 1 credit. Free plan credits are one-time. Pro plan credits refresh monthly.

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Best Practices

  1. Validate at signup - Catch invalid emails before they enter your database
  2. Use suggestions - Show typo corrections to users (e.g., “Did you mean gmail.com?”)
  3. Block disposable emails - Prevent abuse from temporary email services
  4. Handle role addresses - Consider whether to allow info@, support@, etc.
  5. Re-validate periodically - Email addresses can become invalid over time

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Next Steps

Validation API Reference

Complete API documentation for email validation

Bulk Validation

Validate multiple emails at once