Reveal all the domains that use the same mail server

With a single API call, make sure that your website doesn't share the mail server with any suspicious or blacklisted domains – hosts with a dubious reputation may affect email delivery.

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100 free credits monthly. No credit card required.

1,473,142,430Domains and subdomains
142,703,533MX records updated daily
2,131Satisfied customers


  • Сomprehensive & up-to-date

    We provide service based on the world’s largest constantly updated database with 1,473,142,430 domains and subdomains, 142,703,533 MX records updated daily.

  • Fast response & easy integration

    A fast and easy-to-use API for quick access to the largest database. All the results are duly parsed and normalized to a consistent format such as JSON and XML for easy integration with your business processes.

Practical usage

Blacklisting prevention

Blacklisting prevention

Prevent your mail server from being blacklisted. Hosts with dubious reputation may affect email delivery. By using the Reverse MX API service you can identify spamming, phishing and other poor reputation sites on your host.

Improve security

  • Uncover connected domains that may otherwise seem unrelated.
  • Analyze 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

Get access to the biggest Passive DNS Database

The passive DNS database is a large Historic DNS repository with 2 billion hostnames and hundreds of billions of Historic DNS Lookups. Our comprehensive passive DNS database allows finding out all historical DNS data points for any hostname and ip address.

Download database
Reverse MX API | Whois XML API

Get 100 free credits monthly. No credit card required.

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Enterprise API Packages

API access through WhoisXMLAPI can be purchased as an annual subscription. The access pricing is based on the number of queries, which is measured monthly with per-minute rate limits. The pricing structure gives predictability to business planning and solution architecture.

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