Error: open resolver

Zero Trust 1.1.1.1
1

The public DNS resolver is unable to get a valid TXT record and returns an error for every request:

~ $ dig 164.237.25.223.zen.spamhaus.org @1.0.0.1 TXT +short
"Error: open resolver; https://www.spamhaus.org/returnc/pub/2400:cb00:20:1024::8d65:4b94"

Also http request:

~ $ curl -H 'accept: application/dns-json' 'https://cloudflare-dns.com/dns-query?name=164.237.25.223.zen.spamhaus.org&type=TXT'
{"Status":0,"TC":false,"RD":true,"RA":true,"AD":false,"CD":false,"Question":[{"name":"164.237.25.223.zen.spamhaus.org","type":16}],"Answer":[{"name":"164.237.25.223.zen.spamhaus.org","type":16,"TTL":2100,"data":"\"Error: open resolver; https://www.spamhaus.org/returnc/pub/172.71.181.37\""}]}

while the 8.8.8.8 public resolvers show up-to-date information:

~ $ dig 164.237.25.223.zen.spamhaus.org @8.8.8.8 TXT
; <<>> DiG 9.10.6 <<>> 164.237.25.223.zen.spamhaus.org @8.8.8.8 TXT
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 46280
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
164.237.25.223.zen.spamhaus.org. IN	TXT
2

Why do you think it is a valid record? Neither Google nor the authority return anything.

nslookup -type=txt 164.237.25.223.zen.spamhaus.org a.gns.spamhaus.org
Server:  UnKnown
Address:  199.247.16.193

*** UnKnown can't find 164.237.25.223.zen.spamhaus.org: Non-existent domain
3

You can further check it at DNS Checker - DNS Check Propagation Tool

The authoritative nameservers simply provide different responses to different nameservers. Among them Cloudflare and 9.9.9.9.

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4

Spamhaus does not allow queries from public/open resolvers. See Successfully accessing Spamhaus' free blocklists using a public DNS - Spamhaus Technology.

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