DNS Troubleshooting Guide: Fix Domain, Website, and Email Connection Problems

Overview

The Domain Name System, or DNS, connects a human-readable domain such as example.com to services such as a website, email provider, or application. Your domain registrar, DNS provider, and web host may be three different services, so the first step in troubleshooting is identifying where DNS is actually managed.

There are two common control points:

• Nameservers: These tell the internet which DNS provider holds the authoritative records for your domain.
• DNS records: These specify where the website, email, and subdomains should connect.

A useful rule is to change records only at the authoritative DNS provider. Editing records in a hosting dashboard will not help if the domain uses different nameservers, and changing nameservers can replace or bypass records that were previously working.

Before making changes, record the current configuration. Save screenshots or export the zone if your provider supports that option. Note the current nameservers, website IP address, email provider, verification records, and any custom subdomains. This gives you a recovery reference if a change creates a new problem.

Checklist by scenario

The domain does not open

1. Confirm that the domain is active and has not expired or been placed on hold by the registrar.
2. Check the domain's nameservers at the registrar. They should match the DNS provider you intend to use.
3. At that DNS provider, confirm that the root domain has the correct A record, usually pointing to the web server's IPv4 address.
4. If the host supplied an IPv6 address, check whether an AAAA record is also required. An incorrect AAAA record can send some visitors to the wrong server even when the A record is correct.
5. Check whether the www hostname has a CNAME pointing to the intended hostname or an A record pointing to the correct server.
6. Test both the root domain and www separately. They are separate DNS names and may have different records.

To connect a domain to a website, use the exact values supplied by the hosting provider rather than guessing an IP address. If the host uses a platform-specific CNAME, follow that platform's instructions; do not replace it with an unrelated A record unless the provider explicitly says to do so.

The site works on one network but not another

1. Compare results using a DNS lookup tool, a command-line lookup such as dig or nslookup, and a DNS propagation checker.
2. Check the authoritative nameservers directly, not only the result returned by your local internet provider.
3. Clear the device and browser DNS cache, then test from a different network or mobile connection.
4. Consider the record's TTL, or time to live. Resolvers may continue showing an earlier answer until its cached period ends.

Propagation is not a single global switch. Different resolvers can update at different times, and a change may appear correct in one location before another. Avoid repeatedly changing the same record while waiting, because each new change makes the final state harder to diagnose.

Website email stopped working

1. Confirm which provider handles email for the domain.
2. Review the MX records and remove obsolete or conflicting entries only when you are sure they are no longer needed.
3. Check the priority values if the provider supplied more than one MX record. Lower numbers generally indicate higher priority, but follow the provider's published instructions.
4. Make sure the MX records are entered for the correct domain and are not accidentally attached to a subdomain.
5. Review any required SPF, DKIM, and DMARC records. These are TXT records and may be needed for sending authentication, even though they do not deliver incoming mail.

Do not point MX records to your web host simply because the website is hosted there. Website hosting and business email hosting can be separate services. If email worked before a website migration, preserve the existing MX and email-authentication records unless the email provider is changing too. For related setup guidance, see how to create a custom domain email address for your business.

A subdomain or application is unavailable

1. Check that the subdomain record exists, such as shop.example.com or app.example.com.
2. Use either an A record for an IP address or a CNAME for a hostname, as instructed by the service.
3. Look for conflicting records. A hostname should not have both a CNAME and other incompatible record types at the same name.
4. Confirm that the application, hosting account, and SSL certificate are configured to accept the subdomain.

DNSSEC reports an error

DNSSEC adds validation to DNS responses, but an outdated or mismatched DS record can make a domain fail validation. If DNSSEC errors began after changing nameservers, compare the DS record at the registrar with the DNSSEC configuration at the authoritative provider. Do not remove DNSSEC casually; first follow the provider's documented rollover or deactivation process. If you cannot verify the correct key values, pause and contact the DNS provider before making further changes.

What to double-check

Use this record-by-record review before and after a DNS change:

• NS: Are the registrar nameservers the ones used by the intended DNS provider?
• A and AAAA: Do they point to the current server, and are old hosting addresses removed?
• CNAME: Does the target hostname match the provider's instructions, without adding a protocol such as https://?
• MX: Do the records point to the current email provider with the correct priorities?
• TXT: Are SPF, DKIM, DMARC, ownership verification, and other service records still present and correctly formatted?
• TTL: Is there enough time for caches to expire before you judge the result?
• SSL and hosting: Does the web host recognize the domain and issue a certificate for both the root domain and required subdomains?

After editing, test the actual services rather than relying only on a lookup. Load the website over HTTPS, send and receive a test email, sign in to important subdomains, and verify third-party services that depend on TXT records.

Common mistakes

• Editing DNS in the wrong dashboard: The registrar may not be the authoritative DNS provider.
• Replacing nameservers without copying records: This can remove website, email, verification, and subdomain records at once.
• Using a CNAME at the root when the provider requires an A record: Root-domain support varies by DNS provider.
• Leaving old MX records in place: Multiple providers can create unpredictable email delivery.
• Changing several records at once: Make one logical change, document it, and test before continuing.
• Assuming propagation is instant: Cached answers can persist according to TTL and resolver behavior.
• Forgetting the hosting migration details: A new server may require a new IP, CNAME, SSL setup, or application configuration. Use the website migration checklist when moving hosts.

When to revisit

Revisit this DNS checklist before a website migration, domain transfer, email-provider change, seasonal campaign, or major hosting-plan change. It is also worth reviewing after a redesign, new subdomain launch, security-tool rollout, or unexplained email failure. Hosting dashboards and DNS workflows can change, so confirm the current provider instructions whenever you repeat a setup.

For a practical final pass, export or document the DNS zone, list who controls the registrar and DNS account, confirm the website and email owners, and test every important hostname. Keep the record list with your website backup and security documentation. The website hosting security checklist and backup strategy guide can help complete that wider maintenance process. A documented baseline turns the next DNS problem from guesswork into a short, repeatable diagnosis.