12 Critical DNS Errors That Can Break Your Website (+ Quick Fixes)

DNS errors can take your website offline in seconds. The stats are alarming: 72% of organizations faced a DNS attack in 2024, and nearly half involved DNS hijacking. Attackers manipulate DNS queries to redirect users to malicious servers, creating major vulnerabilities.

When DNS functions correctly, everything from email delivery to web browsing works smoothly. But DNS problems can trigger downtime, slow performance, failed connections, and even data breaches. These issues are often caused by simple misconfigurations — giving attackers exactly what they want.

In this guide, we’ll walk through 12 of the most common DNS issues, explain what causes DNS errors, and share tips on how to fix DNS errors quickly. Whether you’re dealing with cryptic messages or unexplained outages, this DNS troubleshooting reference will help keep your site running smoothly.

This error means a DNS lookup failed entirely — the system couldn’t find any IP address for the requested domain.

The “NXDOMAIN” label stands for “Non-Existent Domain.” That could mean:

• A typo in the domain name
• An unregistered or expired domain
• Corrupted local DNS cache
• Wrong DNS server settings
• Conflicting VPN, antivirus, or firewall rules
• A misconfigured hosts file
• Chrome-specific flags interfering with DNS

This results in complete inaccessibility. Chrome shows “This site can’t be reached,” while Firefox displays “We’re having trouble finding that site.”

• Double-check the domain name
• Flush DNS cache (ipconfig /flushdns on Windows, Terminal commands for macOS)
• Renew your IP address
• Switch to public DNS (e.g., 8.8.8.8 or 1.1.1.1)
• Check your hosts file
• Temporarily disable VPN/firewall
• Confirm that A records are present and point to a valid server

Unlike NXDOMAIN, SERVFAIL occurs when the DNS server can’t complete a valid lookup — even though the domain exists.

• DNSSEC validation failures (expired or mismatched keys)
• Zone file misconfigurations
• Missing glue records
• Overloaded or offline authoritative name servers
• Excessive CNAME chains (recursive depth exceeded)
• Firewall or routing issues

Users and bots can’t access your site or send email. SERVFAIL also harms SEO since search engines can’t crawl your domain consistently.

• Validate DNSSEC signatures
• Review and correct zone file syntax
• Check glue records and name server delegation
• Monitor server loads and ensure redundancy
• Keep CNAME chains under eight entries

A REFUSED error means the DNS server deliberately rejected your query.

• Access restrictions or security policies
• IP filtering or country-based blocks
• Unauthorized requests (e.g., zone transfers)
• Protocol mismatches (e.g., blocked TCP connections)
• Firewall rules or DNS server misconfigurations

These dns problems cause website inaccessibility and service interruptions. Users might see “ERR_CONNECTION_REFUSED,” and apps relying on DNS stop functioning.

• Flush your local DNS
• Switch to automatic or public DNS settings
• Test with Google (8.8.8.8) or Cloudflare (1.1.1.1)
• Check firewall and port rules (UDP/TCP on port 53)
• Verify that your registrar and hosting provider have matching name servers

This happens when the DNS query times out before getting a response — often with no visible error code.

• Sluggish or overloaded DNS servers
• Bad routing paths or high latency
• DNS servers located too far geographically
• Blocked or filtered DNS traffic on your network
• Resource-starved DNS resolvers

DNS timeouts often go unnoticed in logs but cause significant slowdowns. Google reports that bounce rates increase dramatically when page load times exceed 3–5 seconds.

• Use multiple DNS servers for failover
• Choose optimized, low-latency DNS services
• Monitor DNS response time using tools like DNSPerf
• Reduce TTLs to minimize wait times
• Consider using a CDN for geo-distributed resolution

If your MX records are misconfigured, your organization’s email can stop working completely.

• MX records pointing to CNAMEs (which is invalid)
• Syntax errors or missing dots in hostnames
• Duplicate records or incorrect priority values
• Records pointing to decommissioned servers
• Failure to verify domain ownership

Email bouncebacks, spam flags, and delivery failures — especially with providers like Gmail or Outlook that rely on strict DNS validation.

• Point MX records to A records (not CNAMEs)
• Use priority values properly (lowest = primary server)
• Confirm ownership via DNS TXT records
• Clean up outdated or duplicate entries
• Test configurations with MXToolbox

Reverse lookups (rDNS) map IPs back to domain names. They’re essential for email trust and authentication.

• Missing PTR records
• Mismatched forward (A) and reverse (PTR) records
• Dynamic IPs without PTR setup
• Hosting providers who don’t support custom rDNS
• Blacklisted IPs

• Ask your ISP or host to assign a valid PTR
• Use static IPs for outbound email
• Match A and PTR entries exactly
• Set up SPF, DKIM, and DMARC for added trust

DNS changes don’t apply instantly — they take time to propagate worldwide.

• High TTL (Time-to-Live) values
• ISP-level caching beyond your control
• Delays in global DNS root servers
• Slow regional infrastructure

Users may see outdated content or get bounced emails. It can also confuse search engines during site migrations.

• Lower TTL to 300–600 seconds before planned changes
• Monitor progress using DNSChecker or WhatsMyDNS
• Clear local and browser DNS caches
• Consider CDN services to accelerate resolution

This broad category includes all the little mistakes that quietly break DNS behind the scenes.

• Typos in IP addresses
• Multiple CNAMEs assigned to one name
• Forward and reverse mismatches
• Records still pointing to legacy infrastructure

These silent dns problems can lead to man-in-the-middle attacks, downtime, or redirect errors.

• Audit your DNS regularly
• Use a DNS provider that tracks changes and history
• Use dig or nslookup to validate records manually
• Implement DNS failover for key services

TTL settings control how long records are cached by resolvers. Longer values reduce load but slow down updates.

• Leaving default TTL at 86,400 seconds (24 hours)
• Not lowering TTL before major changes
• Trying to cut down on query volume

High TTL means fast performance and low query cost — but DNS changes can take days to propagate.

Use 1800–3600s TTL for dynamic records, and lower it to 300s before migrations.

Open resolvers respond to queries from anyone. That makes them vulnerable to DNS amplification and spoofing attacks.

• Misconfigured routers or firewalls
• DNS servers allowing unrestricted recursion
• No ACLs (Access Control Lists) in place

You could unknowingly participate in DDoS attacks or expose your infrastructure to poisoning.

• Disable recursion on public-facing servers
• Apply IP-based restrictions
• Use response rate limiting (RRL)
• Follow BCP 38 to prevent spoofed traffic

Old DNS records pointing to inactive servers or services can quietly cause resolution failures or security risks.

• Poor DNS hygiene
• No cleanup after server decommissioning
• Lack of change management during infrastructure updates

Stale records can be exploited in subdomain takeovers or result in traffic being routed to unintended destinations.

• Scheduled DNS audits
• DNS scavenging tools
• Manual review of critical entries
• Decommissioning workflows tied to DNS updates

Your authoritative name servers are the final source of truth. If they’re left open, you risk total domain compromise.

• Allowing recursion on authoritative servers
• No firewall or ACLs on zone transfers
• No DNSSEC signing

From cache poisoning to DDoS, unsecured name servers open the door to widespread abuse.

• Turning off recursion
• Restricting zone transfers with TSIG
• Using DNSSEC to verify data integrity
• Placing primaries behind firewalls or as hidden masters

DNS errors can feel like a black box — until they take your site offline or break your email system. But most DNS errors are preventable with the right setup and regular maintenance.

By understanding what causes DNS errors, performing consistent dns troubleshooting, and knowing how to fix DNS errors when they appear, you gain control over one of the most critical layers of your digital infrastructure.

From slow lookups to hijacked records, these common DNS issues don’t have to catch you off guard. Bookmark this guide, audit your records, and stay ahead of DNS problems before they impact your business.