DNS Troubleshooting Articles
Use these articles when something is broken and you need a step-by-step path to isolate the cause and verify the fix.
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DNS Propagation Checker
Compare answers across public resolvers.
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Review SPF, DMARC, DKIM, MTA-STS, TLS-RPT, and BIMI together.
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Troubleshooting
What Is a Dangling CNAME?
Learn what a dangling CNAME is, why it can create subdomain takeover risk, what patterns to look for, and how to clean up stale aliases safely.
Common Glue Record Problems: DNS Delegation Issues Explained
A troubleshooting guide to glue record issues, including in-bailiwick nameservers, missing glue, delegation mismatches, and how to fix DNS resolution failures.
Common PTR Record Problems: Reverse DNS Issues Explained
A practical guide to PTR record problems, including missing reverse DNS, forward-confirmed reverse DNS, hostname issues, and how PTR impacts email deliverability.
How to Check DKIM Selectors (Step-by-Step Guide)
Learn how to find and check DKIM selectors, query DNS correctly, and troubleshoot missing or invalid DKIM records with real examples.
How to Check DNS Propagation (Step-by-Step Guide)
A practical step-by-step guide to checking DNS propagation, including what to compare, how TTL affects results, and how to interpret inconsistent answers.
How to Check DNSSEC (Step-by-Step Guide)
A practical DNSSEC checking guide covering DNSKEY and DS records, signature validation, and how to verify the full DNSSEC chain of trust.
How to Check MTA-STS (Step-by-Step Guide)
Learn how to validate MTA-STS using both the DNS TXT record and the hosted HTTPS policy file, including common issues and troubleshooting steps.
How to Check Reverse DNS for Mail (Step-by-Step Guide)
A practical guide to checking reverse DNS for mail servers, including PTR records, forward confirmation (FCrDNS), and what good mail-related reverse DNS looks like.
How to Check Whether an SPF Record Is Too Complex
A practical SPF troubleshooting guide covering recursive includes, DNS lookup limits, redirect behaviour, and how to simplify an overly complex SPF policy.
How to Interpret DMARC Reports (Step-by-Step Guide)
A practical guide to interpreting DMARC reports, identifying legitimate senders, spotting spoofing, and deciding when to move toward enforcement.
How to Publish BIMI (Step-by-Step Guide)
A practical guide to publishing BIMI, including record format, selector usage, logo requirements, and what to validate before rollout.
How to Read Email Headers (With Examples)
Learn how to read email headers with real examples, including Authentication-Results, Received headers, Return-Path, and how to trace message flow.
How to troubleshoot DMARC failures
A practical DMARC troubleshooting guide covering missing records, alignment problems, policy interpretation, and common causes of DMARC failure.
How to troubleshoot MX record problems
A practical MX troubleshooting guide covering missing MX records, wrong targets, bad priorities, and how to verify mail routing during migrations.
How to Troubleshoot SPF Failures: Complete Step-by-Step Guide
A comprehensive SPF troubleshooting guide covering missing records, multiple SPF issues, DNS lookup limits, includes, redirects, and how to fix SPF failures.
When to use SPF flattening
Learn when SPF flattening may help, when it creates more operational risk than value, and what to review before using it in production.
Why does a domain have multiple MX records?
Learn why multiple MX records are normal, how priority works, and what to check when a domain publishes more than one receiving mail host.
Why does one hostname resolve to multiple IP addresses?
Learn why a single hostname may return multiple A or AAAA answers and how to interpret that in DNS and email troubleshooting.