DNS
DNS record guides
Problem-first guides for the records that affect email — add them correctly, verify propagation, and link to tools when you need a second opinion.
Record types
Where mail is delivered — priorities, providers, verification.
SPF, DKIM, DMARC, verification — and the one-SPF rule.
Aliases, apex limits, DKIM CNAMEs.
Point hostnames to IPv4 — sites, mail hosts, PTR.
IPv6 addresses for dual-stack setups.
Reverse DNS at your host — not the registrar.
Authorised senders, includes, and the 10-lookup limit.
Publish your public key — avoid truncation.
Policy, reports, and rollout from p=none to reject.
Nameservers at the registrar — delegation and cutovers.
Propagation guides
TTL, timelines, and checking five resolvers at once.
How long A changes take and what to do if stuck.
Email during MX changes, TTL, verification.
SPF, DKIM, DMARC — verify auth records are live.
DKIM CNAMEs, chains, and TTL.