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Comment by buckminster | Hacker News Reader

A friend of mine has a simple static hobby website on his own .net domain. It isn't reachable through CloudFlare DNS. This has been true for over two months. Google DNS can see it, as can my ISP's.

I recently noticed that his self-hosted email is sometimes being flagged as spam because it lacks spf.

Is CloudFlare filtering their DNS results, maybe against a spam blacklist?

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Can you share the domain name so we can investigate?

I can't share the domain name but its DNS servers are:

  ns3.cisws.nl
  ns6.cis-websolutions.nl

Sharing the domain is usually critical.

Picking a random domain hosted on those nameservers, mdfs.net, it looks like, of the 4 IPs, 2 are down and 1 of the remaining ones doesn't support TCP.

http://dnsviz.net/d/mdfs.net/W48OcQ/dnssec/ https://ednscomp.isc.org/ednscomp/4040283963

1.1.1.1 is less tolerant than some resolvers of that level of breakage.

https://community.cloudflare.com/t/ipv6-timeouts-appear-to-b...

Thanks for having a look. If I understand that correctly the DNS servers are returning IPv6 addresses for themselves, which aren't functioning. So he needs to get his host to stop returning the IPv6 addresses (or to fix IPv6).

Yup. And also one of the IPv4 IPs isn't doing TCP.

I'm not sure nothing else is wrong, but the IPv6 issue is likely why 1.1.1.1 is having trouble resolving it.

Perhaps his DNS servers just wont talk to 1.1.1.1 for $reasons?

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