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Reverse MX

Find domains sharing the same mail server.

Reverse MX

Find domains sharing the same mail server.

Enter mail server, domain name, IP address (IPv4 and IPv6) or subnet. Example: dnslytics.com or alt1.aspmx.l.google.com

Handle input as domain name instead of MX record

We first check your input against our list of known mail servers (MX records). If we do not find any mail servers matching your input we will treat your input as a domain name and perform a live MX lookup.

Tool description

Every domain name capable of receiving emails has one or more mail servers (MX record). Use the Reverse MX tool to find domains sharing the same mail server. It shows a maximum of 2,500 connected domains (depending on your membership type). For subnets it shows a maximum of 255 IP addresses. Just type a mail server, domain name, IP address or subnet and click the Go button. Both IPv4 and IPv6 addresses are supported. For the subnet view you have to type the subnet in the form of x.x.x for IPv4 subnets and x:x:x:x for IPv6 subnets.

Example objectives

  • Discover relations like ownership between domain names.
  • Monitor and discover mail servers on the same subnet.
  • Perform research on malicious mail servers.
  • Monitor new and removed domains on mail servers of competitors.


Q: How do you decide a mail server is hosted on an IP address?
A: First we identify a mail server when it is actually configured in the DNS for a domain. For example if mx1.domain.com is a MX record for domain.com, we identify mx1.domain.com as a mail server. After we identify a mail server we perform an A and AAAA lookup of the mail server.

Q: How often do you resolve the MX records for a domain?
A: Our DNS crawlers try to resolve every domain name once per month.

Q: How many mail servers do you have?
A: We have 55+ million active mail servers on file.

Q: How many domains do you have?
A: We have access to all gTLD (ex com, net, org) and nTLD (ex xyz, berlin, nyc) daily zone files. For ccTLD (ex de, fr, eu) our coverage is between 40% and 70% depending on the ccTLD.

Q: Is this tool available for all Top Level Domains?
A: Yes, the Reverse MX tool returns all domains.

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