DNS and Whois Guides

How to look things up and how to read the results, with examples. Every guide can be tried right away in Web dig, in your browser.

• How to Check MX RecordsWhen email isn’t arriving or can’t be sent, the MX record is the first thing to suspect. Here is how to look it up and how to read the result.
• How to Check DNS Propagation“I changed my DNS, but it still shows the old value.” The cause is usually caching. Here are the steps to find out how far your change has spread.
• How to Look Up an SPF RecordSPF is a mechanism that declares which servers are allowed to send email for your domain. It is written in a DNS TXT record, so you can check it by looking up TXT.
• How to Do a Whois LookupWhois is how you look up a domain’s registration information. Use it when you want to know the expiry date or the name servers.
• How to Use the dig Commanddig is a command that sends DNS queries and shows the results. Here are the basics and the forms you will use most.
• How to Do a Reverse Lookup (PTR)Normal DNS finds the IP address from a hostname. The reverse, finding the hostname from an IP address, is called a reverse lookup (PTR).
• DNS Record Types ExplainedDNS has different record types for different purposes. Here is a list of the common ones, what they mean and when to use them.