Very often problems like ‘my website is not working’ or ‘I did not get any emails’ are caused by improperly set up dns records or expired domain. At my work, I’m permanently dealing with incorrectly set up dns records. There are available services like intodns.com which you can use to check dns records for domain. But what to do, if you have problem with reverse dns? Or you want to check, if your reverse delegation is set up correctly?