DNS records
What each record does, tied to deliverability.
What is a DNS record? DNS records explained
Every part of how your domain works is a DNS record. The anatomy of one, the types you will actually meet (A, CNAME, MX, TXT, NS), and why a wrong one breaks mail silently.
What is an MX record? (and why a wrong one loses mail)
The MX record decides where your inbound email is delivered. How preference works, the null-MX and no-CNAME rules, and why a wrong MX loses mail with no warning.
What is an A record? (A and AAAA, explained)
An A record points a name to an IPv4 address, AAAA to IPv6. Why you cannot CNAME your apex, and how forward-and-reverse DNS decides whether Gmail trusts your mail.
What is a CNAME record? (and why not at your apex)
A CNAME points one name at another. Why it cannot live at your apex, why MX and NS must never point to one, and how email providers use CNAMEs to run your DKIM.
What is a TXT record (and why SPF, DKIM, and DMARC all live in one)?
A TXT record holds free-form text in DNS. It's also where every email-authentication record you publish actually lives. What it is, the quoting and length rules that bite, and how to verify one.
What are NS records? (and why your DNS edit did nothing)
NS records decide which provider answers DNS for your domain. The registrar-versus-host trap behind 'I edited my DNS and nothing changed,' and how to find your real DNS host.
What is an SOA record? (Start of Authority, explained)
The Start of Authority record holds your zone's serial number and timers. What each field does, and why its negative-cache minimum is the reason a new record reads as not found.
What is a PTR record? (reverse DNS, explained)
A PTR record is reverse DNS: it maps an IP back to a hostname. The reverse-DNS tree, why mail servers check it, and why you set it at your IP host, not your DNS panel.
What is an SRV record? (and why email rarely needs one)
An SRV record tells clients where to find a service. Why it does not route mail (MX does), the one place it touches email (client autoconfig), and why most domains never need one.
What is DNSSEC? (and what it protects for email)
DNSSEC cryptographically signs your DNS so answers cannot be forged. What it protects (including your email-auth records), why it is not required for email, and the rollover that takes a domain offline.
DNS propagation and TTL: why your change isn't live yet
DNS propagation is a myth: there is no push, only caching and TTL expiry. Why your DMARC or SPF change is not live everywhere yet, how to pre-lower TTL, and how to check it took.
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