A practical guide to common DNS issues including wrong A records, missing MX records, broken CNAMEs, nameserver mistakes and cached answers.

Quick wins from this guide
  • Find the common failure points
  • Separate DNS issues from hosting issues
  • Use a repeatable troubleshooting process

Wrong A or AAAA record

If a website loads the wrong server, shows a default page or points to an old platform, check the A and AAAA records first. Make sure the hostname you are checking is the exact one being used, such as example.com or www.example.com.

Broken CNAME

A CNAME can break if it points to a hostname that no longer resolves, points to the wrong service or conflicts with other records. CNAME issues often affect www, shop, mail-related subdomains and third-party platforms.

Missing MX or TXT records

If email does not arrive or messages fail authentication, check MX records and TXT records. SPF, DKIM and DMARC are commonly stored as TXT records and are easy to damage when changing DNS providers.

Wrong nameservers

If you edit records in one DNS panel but the domain uses different authoritative nameservers, your changes will do absolutely nothing, which is DNS comedy at its most cruel. Always confirm the NS records and registrar settings.

Next server-side checks

If DNS points to the right place but the website still fails, move on to server checks such as web server logs, redirects, SSL, firewalls and application errors. The CommandLineQuiz Linux Troubleshooting Hub is a useful companion for those checks.

Quick commands to try

dig example.com A
dig example.com MX +short
host -t TXT example.com

Practise the command line side

DNSNow gives you quick web checks. For hands-on Linux command practice, use CommandLineQuiz dig Command Builder, the Linux Troubleshooting Hub and the Bash Scripting Hub.

FAQs

Why is my domain still pointing to the old server?

Common causes include cached DNS, unchanged nameservers, the wrong DNS zone being edited or an old A record still active.

Why is email not working after a DNS change?

Check MX records first, then SPF, DKIM and DMARC TXT records. Also confirm the domain is using the nameservers you edited.

Can DNS cause SSL errors?

Yes. If DNS points to the wrong server, the certificate presented by that server may not match the domain.

Sources and further reading