Reverse MX shows all domains with the same mail server | WhoisXML API

Reverse MX products to identify connected domains via different consumption models

We offer different ways—Lookup, API, Database—to check which domains are connected by a mail server.

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500 free API requests. No credit card required.

4.2 Billion+Domains and subdomains
2 Billion+MX records
52,000+Satisfied customers
11+Years of data crawling

Our reverse MX product line includes:


Simply type in a mail server address on our functional graphical user interface (GUI) to get a list of all the domain names that share it.

Reverse MX Lookup | WhoisXML API
Reverse MX API | WhoisXML API


Reverse MX API allows you to see other domains that share the same mail server via API calls. It can be used in conjunction with existing security systems.

DNS Database Download

Our reverse mail server services glean data from DNS Database Download, one of the most extensive passive Domain Name System (DNS) repositories in the world. As a result of more than 12 years of data crawling, our database has amassed millions of mail server and nameserver records and billions of historical DNS records.

DNS Database Download | WhoisXML API


  • Constantly updated and comprehensive

    The passive DNS database that provides data for our reverse MX services is updated every week, further adding millions of historical DNS records. The database contains more than half a million MX records for billions of domains and subdomains.

  • Responsive and integrable

    Reverse MX API can be easily integrated into existing systems as it supports various programming languages that include JavaScript (JS), Java, C#, NodeJS, Perl, PHP, PowerShell, Python, and Ruby on Rails (ROR). The passive DNS database can also be downloaded in full as a MySQL dump or comma-separated values (CSV) file.

Reverse MX Overview | WhoisXML API

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