Learning Articles
Practical guides and explainers for DNS, email security, certificates, and troubleshooting.
Troubleshooting
Common PTR record problems
A practical guide to common reverse DNS issues and what to check when PTR validation fails.
How to check if SPF is too complex
Learn how to spot overly complex SPF records, recursive includes, and DNS lookup limit risks.
How to check MTA-STS
Learn how to validate MTA-STS using both the DNS TXT record and the hosted HTTPS policy file.
How to interpret DMARC reports
A practical overview of what DMARC reports tell you and how to use them during policy rollout.
How to publish BIMI
A practical overview of what is involved in publishing BIMI for a domain.
Why does a domain have multiple MX records?
Learn why domains publish multiple MX records and how redundancy and priority work in practice.
Why does one hostname resolve to multiple IP addresses?
Understand why a single hostname can return multiple A or AAAA records and when that is expected.
DNS Basics
What is a CNAME record?
Learn what a CNAME record is, how aliases work, and when to use CNAME instead of A or AAAA records.
What is a DNS record?
A practical introduction to DNS records, what they do, and how different record types are used.
What is a PTR record?
Learn what PTR records are, how reverse DNS works, and why PTR validation matters for email systems.
What is a TXT record?
Learn what TXT records are used for, including SPF, verification, and other DNS-based policies.
What is an NS record?
Understand how NS records define authoritative nameservers and why delegation matters.
How to read MX records
Learn how MX records work, what priority means, and how to interpret mail routing records correctly.
Email Security
What is BIMI?
Understand what BIMI is, how it works with DMARC, and why it is used for brand visibility in email clients.
What is DKIM and how does it work?
Understand how DKIM signs outbound mail and how DNS publishes the public key used for verification.
What is MTA-STS?
Learn what MTA-STS is, how it protects SMTP transport, and how it works with DNS and HTTPS.
What is TLS-RPT?
Learn what TLS-RPT is and how SMTP TLS reporting works alongside MTA-STS.
What is DMARC and why should you use it?
Understand DMARC policy, reporting, and how DMARC works with SPF and DKIM to protect your domain.
What is SPF and how does it work?
Learn what SPF is, how SPF records work, and why SPF matters for email authentication and deliverability.