DNS issues can take your website offline in seconds — and they’re more common than most people think.

In 2024, 72% of organizations experienced a DNS-related attack, and nearly half involved DNS hijacking.
When DNS breaks, everything breaks: your site, your email, your analytics, your SEO.

Here’s a breakdown of 12 common DNS errors that can cripple your site — plus how to diagnose and fix them quickly

1. DNS_PROBE_FINISHED_NXDOMAIN

Your DNS lookup completely failed — the system can’t find the domain.

Causes: Typos, expired domains, bad cache, wrong DNS server.
Fixes:

• Double-check spelling
• Flush DNS cache (ipconfig /flushdns)
• Switch to 8.8.8.8 or 1.1.1.1
• Verify A records and hosts file

2. SERVFAIL

The domain exists, but the DNS server couldn’t complete the lookup.

Causes: DNSSEC errors, zone misconfigurations, missing glue records.
Fixes: Validate DNSSEC, fix syntax, check server load, limit CNAME chains.

3. REFUSED

Your DNS query was rejected by the server.

Causes: Access restrictions, firewalls, IP blocks, unauthorized transfers.
Fixes:

• Flush DNS
• Use public resolvers
• Check port 53 settings
• Confirm name servers match

4. DNS Timeouts

No response before the query times out — often no visible error code.

Causes: Slow servers, bad routing, distance, network filtering.
Fixes:

• Use multiple DNS servers
• Pick low-latency providers
• Monitor with DNSPerf
• Reduce TTLs

5. Incorrect or Missing MX Records

Email delivery stops working entirely.

Causes: MX points to CNAMEs or dead servers, syntax errors.
Fixes:

• Point MX to A records
• Verify ownership (TXT)
• Test via MXToolbox

6. Reverse DNS Failures

Breaks email trust and triggers spam filters.

Causes: Missing or mismatched PTR records.
Fixes:

• Ask host for PTR setup
• Match A + PTR
• Use static IPs + DKIM/SPF/DMARC

7. Propagation Delays

DNS updates take hours (or days) to apply worldwide.

Fixes:

• Lower TTL to 300–600s before changes
• Use DNSChecker
• Clear browser/local cache

8. Misconfigured DNS Records

Small mistakes that cause big outages.

Examples: Wrong IPs, duplicate CNAMEs, stale entries.
Fixes:

• Regular audits
• Use DNS history tracking
• Validate with dig or nslookup

9. High TTL Values

Makes changes painfully slow to update.

Fix: Use 1800–3600s normally, drop to 300s before migrations.

10. Open DNS Resolvers

They respond to anyone — leaving you open to DDoS attacks.

Fixes:

• Disable recursion on public servers
• Apply ACLs + rate limits
• Follow BCP38

11. Stale or Orphaned Records

Leftover DNS entries from decommissioned servers = silent security risk.

Fixes:

• Schedule DNS audits
• Use scavenging tools
• Clean up during infra changes

12. Unsecured Authoritative Name Servers

Your “source of truth” for DNS, if left open, can lead to total compromise.

Fixes:

• Disable recursion
• Restrict zone transfers
• Enable DNSSEC
• Hide primaries behind firewalls

Final Thoughts

Most DNS issues come down to simple misconfigurations — but they can cause catastrophic downtime.

• Regular DNS audits
• Secure name servers
• Keep TTLs sane
• Validate DNSSEC
• Test changes before rollout

Keep your DNS clean, monitored, and secured. A few minutes of prevention can save hours (or days) of outage headaches.