Skip to content

Frequently Asked Questions (FAQ)

This section answers common questions about how the MX18 Email Validation API works, its accuracy, and how to use it effectively.

Does the Email Validation API send emails to recipients?

No.
MX18 performs validation using non-intrusive techniques such as syntax checks, DNS lookups, SMTP handshakes, and reputation analysis. No emails are sent to the recipient during validation.

Is email validation performed in real time?

Yes.
Each request is processed in real time and returns a response immediately. This makes the API safe to use during signup flows, onboarding, and pre-send checks.

How accurate are the validation results?

Validation results are highly accurate, but not absolute guarantees.

Email deliverability is influenced by multiple external factors such as:

  • Recipient mailbox behavior
  • ISP filtering policies
  • Sender reputation and sending patterns

MX18 validation should be used as a risk assessment and decision support tool, not a promise of delivery.

What does “catch-all” mean and should I send to those addresses?

A catch-all domain accepts all email addresses, even if the mailbox does not exist.

  • Catch-all addresses can still be valid.
  • They carry higher uncertainty because mailbox existence cannot be confirmed.

Best practice

  • Send to catch-all addresses only if engagement is positive.
  • Revalidate periodically and suppress unengaged catch-all recipients.

Should I block all disposable email addresses?

In most cases, yes.

Disposable or temporary email addresses are commonly associated with:

  • Low engagement
  • Fraud or abuse
  • One-time signups

MX18 recommends blocking or suppressing all addresses flagged as disposable = true.

Can a previously valid email become invalid?

Yes. Email validity changes over time.

Common reasons include:

  • Account deletion by the user
  • Domain shutdown or policy changes
  • Mailbox inactivity or suspension

Revalidation is recommended, especially for inactive or long-lived lists.

How often should I revalidate email addresses?

Recommended cadence:

  • Active users: every 60–90 days
  • Cold or inactive lists: before each campaign
  • Imported or legacy lists: immediately before activation

Avoid revalidating the same address repeatedly within short time windows unless required.

Does validation guarantee inbox placement?

No.
Validation improves deliverability by reducing risk, but inbox placement also depends on:

  • Sending reputation
  • Content quality
  • Engagement history
  • Sending frequency and consistency

Validation should be combined with good sending practices.

Is the Email Validation API compliant with data protection regulations?

Yes.

  • Validation is performed transiently
  • No marketing emails are sent
  • Data is processed securely
  • MX18 follows applicable data protection and privacy regulations

Always ensure your own usage aligns with regional compliance requirements.

Can I use the validation API for bulk lists?

The current endpoint supports single-email validation.
Bulk validation capabilities will be introduced in future iterations.

If you have large-scale validation requirements, contact the MX18 team for guidance.

What happens if the validation service is unavailable?

In the event of a temporary service issue:

  • Handle failures gracefully
  • Avoid sending without validation if possible
  • Retry validation where appropriate

MX18 continuously monitors availability and reliability.

Where can I get help or report issues?

  • Refer to the documentation for detailed guidance
  • Contact MX18 support
  • Reach out to your MX18 account manager for enterprise needs

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