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Email Validation API (Beta)

The MX18 Email Validation API helps you assess the quality and deliverability risk of an email address before you send. It evaluates whether an address can safely receive email and provides a clear recommendation on whether you should send, review, or block it.

Email validation is a critical step for maintaining strong sender reputation, improving inbox placement, and ensuring your engagement metrics reflect real user behavior.

What this API does

Given an email address, the MX18 Email Validation API returns:

  • A quality score (0–100)
  • A trust band indicating risk level
  • A suggested action (send, do_not_send)
  • A set of diagnostic insights, such as:
  • Catch-all detection
  • Disposable email detection
  • SMTP-level mailbox validation
  • Domain reputation assessment

This allows you to make informed, automated decisions before sending emails.

When should you use email validation?

You should validate email addresses at multiple points in your lifecycle:

  • Before sending campaigns (transactional or promotional)
  • During user signup or onboarding
  • While importing or migrating email lists
  • Before warming up new IPs or domains
  • As part of ongoing list hygiene

Validation is especially important when: - You’re sending at scale - You’re onboarding new customers or lists - You’re seeing increased bounce or spam complaint rates

Why email validation matters

1. Better inbox placement

Mailbox providers closely track bounce rates and sending behavior. Sending to invalid or risky addresses can quickly damage your sender reputation.

By validating upfront, you: - Reduce hard bounces and unknown-user errors - Avoid repeated delivery attempts to non-existent mailboxes - Protect IP and domain reputation - Increase the likelihood of landing in the inbox instead of spam

2. Higher user engagement

Email engagement metrics only matter if emails reach real users.

Validation helps you: - Focus sends on deliverable addresses - Avoid disposable or low-quality emails - Improve effective open and click-through rates - Build cleaner, more responsive audiences

3. Lower operational and sending costs

Invalid emails still consume sending volume, retries, and processing effort.

Using validation: - Reduces wasted send volume - Minimizes retry queues and bounce handling - Improves suppression accuracy - Keeps campaigns efficient and predictable

How MX18 validation works (high level)

MX18 combines multiple signals to assess each email address:

  • Syntax and domain checks to ensure format correctness
  • SMTP validation to verify mailbox existence (without sending mail)
  • Catch-all detection to identify domains that accept all addresses
  • Disposable email detection to flag temporary inbox providers
  • Domain reputation analysis to assess historical risk patterns

The result is distilled into a single response that’s easy to automate against.

How validation fits with MX18 Mail Send

Email Validation is designed to work seamlessly with MX18’s Mail Send APIs:

  • Uses the same authentication header
  • Follows consistent API conventions
  • Can be called synchronously before enqueueing mail
  • Complements suppression lists and engagement filters

Typical flow:

  • Validate email address
  • Decide whether to send, or suppress
  • Send mail only to approved recipients

What’s next

  • Authentication – how to authenticate requests using your MX18 Email Validation API key
  • Validate an Email – endpoint details and examples
  • Understanding the Response – how to interpret scores, trust bands, and insights
  • Best Practices – how to use validation effectively at scale

Note: The Email Validation API is currently in Beta. While accuracy is high, we recommend using it as part of a broader deliverability and list hygiene strategy.

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