Published: 28.09.2026
When a domain does not open, DNS is the first suspect. Fortunately, a handful of checks quickly show where the problem sits. This guide gives you a simple order of checks that works for most cases.
First, define the symptom
- "Server not found" or similar means the name is not resolving, a DNS problem.
- A timeout or connection refused means the name resolves, but the server does not answer.
- A certificate warning means the DNS works but the certificate does not match.
- The wrong site appears when the name points to the wrong IP address or to an old server.
Step 1: Check that the domain is active
Make sure the domain has not expired and is not suspended. Look at the status in the client area or in a public domain lookup. An expired domain often shows a parking page or stops resolving.
Step 2: Check the name servers
Look at the name servers of the domain at the registrar and compare them with those at your DNS provider. If you changed them recently, the change needs time to spread. If they are wrong, the DNS zone you edit is not the one the internet reads.
Step 3: Query the records
Use the tools nslookup or dig to ask for the A, AAAA, MX and TXT records of the domain. Ask a public resolver and also the authoritative name server directly. If the authoritative server gives the right answer but a public resolver gives another, you are looking at caching.
Step 4: Compare with what you expect
- A record should point to your server IP address.
- www should have its own A record or a CNAME to the main name.
- MX records should point to the mail servers.
- Duplicate or conflicting records cause random behaviour; remove old ones.
Step 5: Think about caching and TTL
Resolvers keep answers for the time set in the TTL value. If you changed a record with a long TTL, some users still see the old address until it expires. Your own computer and browser have caches too. Flush the local DNS cache and try another network or a mobile connection to see a different resolver.
Step 6: Check the server side
If the domain resolves to the right IP but the site still does not open, test the server itself: open it by IP address, check that the web server is running, that the firewall allows ports 80 and 443 and that the site is configured for this domain name.
Common mistakes
- Editing the DNS zone at the registrar while the name servers point elsewhere.
- A CNAME placed on the root of the domain next to other records.
- A missing trailing dot in a hostname value in a zone file.
- Forgetting the AAAA record that still points to an old IPv6 address.
- DNSSEC data at the registrar that does not match the zone after a DNS move.
E-mail DNS problems
If mail is not delivered, check the MX records first, then SPF, DKIM and DMARC. Make sure the reverse DNS of the sending server matches its name.
How long does propagation take?
Most record changes appear within minutes to a few hours. Changes of name servers can take longer. Lower the TTL a day before a planned move and the switch will be fast.
When to contact support
Send the domain name, the time, the exact error, and the output of your DNS queries from two different networks. Clear data lets support find the cause faster.
Frequently asked questions
Why does the site work for me but not for others? Your cache may still have the old or the new record. Compare results from different networks.
Can I speed up propagation? You cannot force other resolvers, but a low TTL set in advance makes changes quick.
Is there a tool that checks everything? Online DNS checkers query many locations and show differences at a glance.
