Verification Types

Understanding verification results is crucial for making informed decisions about your email data. This guide explains each result type and provides recommendations for handling them.

Status Types

Every verification returns one of four primary statuses:

Valid

{
  "status": "valid",
  "result": {
    "deliverable": true,
    "smtp_valid": true
  },
  "score": 0.95
}

Meaning: The email address exists and can receive messages.

Recommended Action: Safe to send. Add to your active mailing list.

Confidence Level: High (score typically > 0.8)

Invalid

{
  "status": "invalid",
  "result": {
    "deliverable": false,
    "reason": "mailbox_not_found"
  },
  "score": 0.10
}

Meaning: The email address cannot receive messages.

Common Reasons:

• Mailbox doesn't exist
• Domain doesn't exist
• Invalid email format
• Domain has no mail server

Recommended Action: Remove from your list immediately. Sending to invalid addresses damages your sender reputation.

Unknown

{
  "status": "unknown",
  "result": {
    "deliverable": null
  },
  "score": 0.50
}

Meaning: We couldn't determine the email's validity with certainty.

Common Causes:

• Mail server timeout
• Temporary server issues
• Greylisting in effect
• Server blocking verification attempts

Recommended Action: Try verifying again later. If persistently unknown, use caution or remove from high-priority campaigns.

Accept All (Catch-all)

{
  "status": "accept_all",
  "result": {
    "catchall": true,
    "deliverable": null
  },
  "score": 0.60
}

Meaning: The domain accepts all emails, so we can't confirm if this specific mailbox exists.

Recommended Action: Keep in your list but monitor for bounces. Consider A/B testing before large sends.

Result Fields Explained

deliverable

valid_format

Indicates whether the email follows valid syntax rules.

// Valid formats
"user@example.com"          // true
"user.name@example.co.uk"   // true
"user+tag@example.com"      // true

// Invalid formats
"user@"                     // false
"@example.com"              // false
"user@.com"                 // false

valid_domain

Indicates whether the domain exists and is properly configured.

valid_mx

Indicates whether the domain has mail exchange (MX) records configured.

disposable

Indicates whether the email is from a temporary/disposable email service.

Examples of disposable domains:

• mailinator.com
• 10minutemail.com
• guerrillamail.com
• tempmail.com

Why it matters:

• Users with disposable emails rarely engage
• Often used for spam or abuse
• Low lifetime value
• May indicate fraudulent intent

role

Indicates whether the email is a role-based address (not tied to a specific person).

Common role-based patterns:

Why it matters:

• Multiple people may receive the email
• Higher complaint rates
• Lower engagement metrics
• Some ESP policies restrict role-based addresses

catchall

Indicates whether the domain accepts all email addresses.

Impact:

• Cannot verify specific mailbox existence
• Higher risk of bounces
• May indicate smaller organization

free

Indicates whether the email is from a free email provider.

Examples:

• gmail.com
• yahoo.com
• outlook.com
• hotmail.com

Use cases for this flag:

• B2B vs B2C segmentation
• Lead scoring
• Fraud detection (high percentage of free emails in B2B)

smtp_valid

Indicates the result of SMTP-level verification.

Confidence Score

The score field (0.0 - 1.0) provides an overall confidence rating:

0.0 ──────────── 0.5 ──────────── 0.8 ──────────── 1.0
 │                │                │                │
Invalid     Unknown/Risky     Likely Valid      Valid

Score Ranges

Handling Strategies by Type

For Marketing Campaigns

function shouldIncludeInCampaign(result) {
  // Strict: Only include high-confidence valid emails
  if (result.status === 'valid' && result.score >= 0.8) {
    if (!result.result.disposable && !result.result.role) {
      return true;
    }
  }
  return false;
}

For Transactional Emails

function canSendTransactional(result) {
  // More lenient: Include valid and accept_all
  if (result.status === 'valid') return true;
  if (result.status === 'accept_all' && result.score >= 0.5) return true;
  return false;
}

For User Registration

function allowRegistration(result) {
  // Block disposable and invalid
  if (result.status === 'invalid') return { allow: false, reason: 'invalid_email' };
  if (result.result.disposable) return { allow: false, reason: 'disposable_not_allowed' };
  return { allow: true };
}

Decision Matrix

Use this matrix to decide how to handle different verification results:

Next Steps