Why doesn't my hostname resolve?

Question

Why doesn't my hostname resolve?

Answer

There are several reasons that a server's hostname may not resolve. The most common issues are the server using a hostname for an unregistered domain, the domain's authoritative nameservers not having an A record for the hostname, the domain's authoritative nameservers lacking GLUE records, or the domain's authoritative nameservers being unreachable on UDP port 53.

Additional resources

What is an effective hostname?

How to change the server's hostname from WHM

Add an A Entry for Your Hostname

What are glue records?