Glossary
DNS
MX record
A DNS record naming a host that accepts mail for a domain, with a preference number. Lower preference values are tried first; equal values are load-shared.
Defined in RFC 5321 §5.1.
Where this appears
The lessons that use this term, and what each is for.
Email Authentication FundamentalsHow DNS decides where mail goesRead a domain’s MX records and predict the order a sender will try them in.SPF PractitionerWhat mx and a really costSay what a single mx term costs on a domain with five mail hosts, and why.DMARC PractitionerDomains that send nothingPublish the complete set of records that makes a parked domain unusable for mail.Advanced Email TrustReading a policy fileRead any published policy and say exactly which hosts it permits and for how long.Advanced Email TrustChanging one safelyChange MX hosts or mode under an active policy without making your domain unreachable.Advanced Email TrustWhat breaksName the failure each advanced control introduces, and how it presents.Domain Security FundamentalsThe records worth knowing, field by fieldRead a zone’s SOA, NS, A, CNAME, MX, TXT and CAA records and say what each asserts.DNS Security PractitionerThree kinds of danglingRank a dangling CNAME, NS and MX by what each one hands an attacker.Domain Abuse & ImpersonationThe MX that changes everythingExplain why an MX record on a lookalike is the single strongest escalation signal.Domain Abuse & ImpersonationRanking a queueOrder a day’s findings so the one that matters is worked first.Domain Trust ArchitectureWhat to do with no budgetList the controls that cost nothing but attention, and deploy them in an afternoon.Domain Security PractitionerPosture, domain by domainProduce the assessment table for a mixed estate and rank every finding.