DNS resolves names (example.com) to addresses, through record types: A (IPv4), MX (mail), TXT (SPF/DKIM/verification), CNAME (alias), PTR (reverse). Records carry a TTL that controls caching.
For hosting, DNS failures masquerade as everything else — sites unreachable for some users, mail undeliverable, SSL renewals failing validation. Checking resolution from the outside world (not just from the server) is the diagnostic habit that untangles them.
Frequently asked questions
Why does a DNS change take hours to “propagate”?
Resolvers cache answers for the record’s TTL. Lower the TTL in advance of planned changes and the switch becomes minutes instead of a day.
Which DNS records affect email deliverability?
MX (where mail goes), SPF and DKIM TXT records, DMARC policy, and the PTR (reverse DNS) of the sending IP — receivers check them all.