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Understanding the Response

The MX18 Email Validation API returns a structured response that helps you determine whether an email address is safe to send, requires review, or should be blocked.

This page explains each field in detail and provides guidance on how to act on the results.

Sample response

{
  "email": "exampleuser@gmail.com",
  "score": 100,
  "trust_band": "high",
  "suggested_action": "send",
  "insights": {
    "is_catch_all": false,
    "disposable": false,
    "smtp_valid": true,
    "reputation": "good"
  }
}

Score

The score represents the overall quality and deliverability risk of an email address on a scale of 0 to 100.

  • Higher scores indicate lower risk and higher deliverability confidence.
  • Lower scores indicate increased risk of bounces, spam filtering, or low engagement.

Typical score ranges

Score range Meaning
90–100 High-quality, low-risk address
50–89 Medium confidence; review recommended
0–49 High risk; sending is discouraged

Trust band

The trust_band is a simplified risk classification derived from the score.

Trust band Description
high Address is considered safe to send
low Address is high risk or likely undeliverable

Trust bands allow quick filtering and segmentation without relying solely on numeric scores.

Suggested action

The suggested_action field provides MX18’s recommended next step based on all validation signals.

Action Recommended behavior
send Safe to send emails normally
do_not_send Do not send; suppress this address

How to use suggested actions

  • Use send for primary campaign recipients.
  • Automatically suppress do_not_send addresses.

Insights

The insights object contains diagnostic signals used to calculate the score and recommendation.

is_catch_all

Indicates whether the domain accepts all email addresses regardless of mailbox existence.

Value Meaning
true Domain uses a catch-all configuration
false Mailbox existence could be verified

Catch-all addresses can still be valid but carry higher uncertainty.

disposable

Indicates whether the email belongs to a temporary or disposable email provider.

Value Meaning
true Disposable or temporary email detected
false Permanent email provider

Disposable emails are commonly associated with low engagement and should typically be blocked.

smtp_valid

Indicates whether the mailbox was validated at the SMTP level without sending an email.

Value Meaning
true Mailbox exists and accepts mail
false Mailbox does not exist or could not be verified

SMTP validation is one of the strongest signals for deliverability.

reputation

Represents the historical risk associated with the email’s domain.

Value Meaning
good Low-risk domain with healthy sending patterns
neutral No strong positive or negative signals
poor Domain associated with higher risk

Domain reputation affects inbox placement even when an address is syntactically valid.

A simple example for automated decision-making:

Send

  • trust_band = high
  • smtp_valid = true
  • disposable = false

Do not send

  • trust_band = low
  • disposable = true or smtp_valid = false

Actual thresholds should be tuned based on your use case and risk tolerance.

Important notes

  • Validation results are probabilistic, not guarantees.
  • Catch-all domains may still deliver successfully.
  • Always combine validation with engagement metrics and suppression logic.
  • Revalidate addresses periodically for long-lived lists.

What’s next

  • Best Practices – learn how to apply validation across signup, imports, and campaigns
  • FAQ – common questions and edge cases

Need help? Contact Support or visit https://support.mx18.com