I've introduced today a new DNS check (Glue Mismatch) under NS section. While querying nameservers often they do provide A or AAAA records in additional section of the response to help/speed up host name resolution, those records are named glue records.
You can examine a DNS query to see glue records from command line with
[vitalie@silver ~]$ dig mx redhat.com @ns1.redhat.com ; <<>> DiG 9.3.6 <<>> mx redhat.com @ns1.redhat.com ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2912 ;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 5 ;; QUESTION SECTION: ;redhat.com. IN MX ;; ANSWER SECTION: redhat.com. 600 IN MX 5 mx1.redhat.com. redhat.com. 600 IN MX 10 mx2.redhat.com. ;; AUTHORITY SECTION: redhat.com. 600 IN NS ns2.redhat.com. redhat.com. 600 IN NS ns3.redhat.com. redhat.com. 600 IN NS ns1.redhat.com. ;; ADDITIONAL SECTION: mx1.redhat.com. 600 IN A 184.108.40.206 mx2.redhat.com. 600 IN A 220.127.116.11 ns1.redhat.com. 600 IN A 18.104.22.168 ns2.redhat.com. 600 IN A 22.214.171.124 ns3.redhat.com. 600 IN A 126.96.36.199 ;; Query time: 150 msec ;; SERVER: 188.8.131.52#53(184.108.40.206) ;; WHEN: Wed Nov 3 15:05:56 2010 ;; MSG SIZE rcvd: 202
In this example while querying MX records from ns1.redhat.com I've received the IP addresses of the mail exchangers:
mx1.redhat.com. 600 IN A 220.127.116.11 mx2.redhat.com. 600 IN A 18.104.22.168
Sometimes you may mess up IP addresses for your nameservers (example IPs provided by your nameserves are different by IPs provided by your registrar), this new check should catch this problem.
Check your domain's glue records here: