DNS debugging checklist
Launch day failures often trace to DNS, not application code. Confirm A/AAAA targets, apex CNAME restrictions, and MX priorities before you announce go-live.
Propagation and TTL
Lower TTL before migrations so clients pick up changes faster. Resolvers worldwide refresh on their own schedule—patience plus authoritative checks beats repeated clicks.
Email authentication
SPF, DKIM, and DMARC live in TXT records. A valid MX is useless if SPF excludes your sender IP or DMARC policy rejects aligned messages.
Dependency on network
Lookups hit external resolvers; offline or firewalled environments may fail. Corporate DNS filtering can return synthetic answers unlike public internet results.