For the owner of the site they can check is their DNS is set correctly by going to these locations:
To check from the host's equipment. Login to each DNS server and run
- host domainName.com
ie for our site: linkonus.com these are the results.
[root@ns2 admin]# host linkonus.com
linkonus.com has address 18.104.22.168
linkonus.com mail is handled (pri=10) by mail.linkonus.net
By looking at the previous results you can track down errors. We have seen problems where double entries in DNS get strange results that until you run "host" on the name servers everything apears correct but you get dropped connections ro mail that bounces.