Understanding Scores

Every email verification returns a quality score from 0-100. This score provides a nuanced view of email quality beyond a simple valid/invalid binary.

Score Ranges

Score	Deliverability	Recommendation
80-100	High	Safe to send
50-79	Medium	Proceed with caution
25-49	Low	High risk
0-24	Risky	Do not send

How Scores Are Calculated

The score is calculated using a proprietary algorithm that evaluates multiple factors:

Positive Factors

• Valid email syntax (+10)
• Domain has valid MX records (+15)
• Mailbox verified to exist (+55)
• Known reputable email provider (+10)
• Not using disposable email service (+5)
• SPF record present (+5)
• DMARC record present (+5)

Negative Factors

• Disposable/temporary email domain (-20)
• Catch-all domain (-15)
• Role account (info@, support@, etc.) (-10)

Score Examples

High Score (95)

{
  "email": "[email protected]",
  "valid": true,
  "score": 95,
  "deliverability": "high",
  "disposable": false,
  "role_account": false,
  "catch_all": false,
  "free_email": false,
  "syntax_valid": true,
  "domain_valid": true,
  "mailbox_valid": true,
  "provider": "google",
  "mx_host": "aspmx.l.google.com.",
  "suggestion": null,
  "dns": null
}

This email has everything going for it: valid syntax, established domain, proper MX records, and a verified mailbox.

Medium Score (65)

{
  "email": "[email protected]",
  "valid": true,
  "score": 65,
  "deliverability": "medium",
  "disposable": false,
  "role_account": true,
  "catch_all": true,
  "free_email": false,
  "syntax_valid": true,
  "domain_valid": true,
  "mailbox_valid": false,
  "provider": null,
  "mx_host": "mx1.newstartup.io.",
  "suggestion": null,
  "dns": {
    "has_spf": true,
    "has_dmarc": true,
    "dmarc_policy": "quarantine"
  }
}

The domain is a catch-all (accepts all addresses), so we can't verify the specific mailbox exists. It's also a role account. The email might be valid, but there's uncertainty.

Low Score (20)

{
  "email": "[email protected]",
  "valid": false,
  "score": 20,
  "deliverability": "risky",
  "disposable": true,
  "role_account": false,
  "catch_all": false,
  "free_email": false,
  "syntax_valid": true,
  "domain_valid": true,
  "mailbox_valid": true,
  "provider": null,
  "mx_host": "mx.tempmail.net.",
  "suggestion": null,
  "dns": null
}

Even though domain checks pass, the disposable domain tanks the score and marks it invalid. This is likely a throwaway account.

Using Scores in Your Application

Simple Threshold

const result = await verifyEmail(email);

if (result.score < 50) {
  return { error: 'Please use a different email address' };
}

Tiered Approach

const result = await verifyEmail(email);

if (result.score >= 80) {
  // Full access, auto-verify
  await createAccount(email, { verified: true });
} else if (result.score >= 50) {
  // Require email confirmation
  await createAccount(email, { verified: false });
  await sendVerificationEmail(email);
} else {
  // Reject signup
  return { error: 'Please use a valid email address' };
}

Using Deliverability Rating

const result = await verifyEmail(email);

switch (result.deliverability) {
  case 'high':
    // Safe to proceed
    break;
  case 'medium':
    // Require confirmation
    await sendVerificationEmail(email);
    break;
  case 'low':
  case 'risky':
    return { error: 'Please use a valid email address' };
}

Scores vs. Validity

A high score doesn't always mean valid: true, and vice versa:

Scenario	valid	Score	Reason
Gmail address, verified	true	95	Everything checks out
Disposable, verified	false	20	Works but risky
Catch-all domain	true	60	Can't confirm mailbox
Typo in domain	false	0	Invalid domain

Best Practices

1. Don't rely solely on valid - Use the score for nuanced decisions
2. Set appropriate thresholds - Different use cases need different standards
3. Monitor score distributions - Track average scores to detect trends
4. Combine with other signals - IP reputation, behavior patterns, etc.