At my company (getstream.io) we've been having issues when resolving our domains randomly. After some more investigation it seems some .io nameservers are returning bad results. Specifically ns-a2.io and ns-a4.io. A correct result for crates.io looks like this: $ dig crates.io @ns-a1.io +norecurse ; <<>> DiG 9.11.2 <<>> crates.io @ns-a1.io +norecurse ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18874 ;; flags: qr; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;crates.io. IN A ;; AUTHORITY SECTION: crates.io. 86400 IN NS dns3.easydns.ca. crates.io. 86400 IN NS dns1.easydns.com. crates.io. 86400 IN NS dns2.easydns.net. ;; Query time: 83 msec ;; SERVER: 194.0.1.1#53(194.0.1.1) ;; WHEN: Wed Sep 20 15:33:13 CEST 2017 ;; MSG SIZE rcvd: 127 A bad one looks like the following: dig crates.io @ns-a4.io +norecurse ; <<>> DiG 9.11.2 <<>> crates.io @ns-a4.io +norecurse ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 43223 ;; flags: qr aa; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;crates.io. IN A ;; AUTHORITY SECTION: io. 900 IN SOA a0.nic.io. noc.afilias-nst.info. 1497256201 10800 3600 2764800 900 ;; Query time: 10 msec ;; SERVER: 74.116.179.1#53(74.116.179.1) ;; WHEN: Wed Sep 20 15:34:59 CEST 2017 ;; MSG SIZE rcvd: 105 This has happened last year as well, so I wouldn't recommend running something important on a .io domain: https://news.ycombinator.com/item?id=12813065