DNS Almanac

A weekly record of public DNS answers for company domains.

Once a week, DNS Almanac looks up a fixed set of public DNS records for about a million company domains and keeps the answers. Over time this builds a history of which email, hosting and software providers companies use, and when they change.

If you saw our queries

Our lookups come from probe.dnsalmanac.com (135.148.70.123). For each domain we ask about 25 questions a week: the domain's MX, NS, TXT and A records, its DMARC record, a few common DKIM selectors, and common subdomains such as www, help and status. One lookup goes to a random name, to tell whether the domain answers for every name.

• We only read public DNS records. We don't scan ports, crawl websites or send email to your domain.
• Queries go through our own resolver and are spread across the whole week's run, with a cap on how many any one domain's servers receive per second.
• The whole run is limited to about 500 queries a second across all domains.

Opting out

To stop us looking up your domain, email optout@dnsalmanac.com from an address at that domain, or list the domains in the message. We stop querying within a week and keep a note of the request.

Contact

Questions, concerns or rate problems: contact@dnsalmanac.com. If our traffic is causing you trouble, tell us and we'll slow down or stop.