Reverse MX API checks associated domains via API calls | WhoisXML API

Reverse MX API tells which domain names use a certain mail server

Check which domains link back to a mail server via API calls to avoid hosts with a dubious reputation, improve email delivery, and other purposes.

Get started

500 free API credits. No credit card required.

50 Billion+Domains and subdomains
BillionsMX records
52,000+Satisfied customers
14+Years of data crawling

What is Reverse MX API?

A reverse MX API is a way to check if several domains can be found on a specified mail server through API calls. This information can help verify if a mail server is dedicated or shared across multiple hosts for cybersecurity and marketing ends.

Reverse MX API


  • Comprehensive and up-to-date

    We provide results pulled from our large and constantly updated DNS database with millions MX records updated weekly for billions of domains and subdomains.

  • Fast response and easy integration

    Reverse MX API is a fast and easy-to-use API for quick access to domains with a shared mail server. All the results are duly parsed and normalized to a consistent format such as JSON and XML for easy integration into your business processes.

Practical usage

Blacklisting prevention

Blacklisting prevention

Prevent your mail server from being blacklisted and avoid harm to your email deliverability. Use Reverse MX API to identify bad hosts that may be involved in spamming, phishing, and other malicious activities.

Improve security

  • Uncover connected domains that may otherwise seem unrelated.
  • Analyze the mailing functions of any organization to gather clues about its structure and security vulnerabilities.
  • Do your research on potentially malicious mail servers.
Improve security
DNS Database Download

Reverse MX API gets its data from a huge passive DNS database

Our passive DNS repository contains billions of historical DNS records for billions of domains and subdomains. Access to our passive DNS database can help you find all there is to know about any Internet property and its DNS records.

Request a Quote
Reverse MX API | WhoisXML API

Get 500 free API credits. No credit card required.

Get started

Premium API Services

Our APIs are available in an enhanced version that offers better performance with a dedicated load balancer and a premium endpoint to enable faster throttling for large-scale API deployments.

Learn more

Enterprise API Packages

Reverse MX API is available together with reverse NS, IP, and other domain intelligence APIs as part of an annual enterprise subscription with predictable pricing.

Learn more