Guides
The tools on this site tell you what your configuration currently is. These guides explain what it should be, and why — each one written around a question people hit while using them.
- Why DNS changes take time: propagation and TTL explained Propagation is not a broadcast — it is caches expiring. Here is how TTL controls the wait, and how to plan a migration around it.
- SPF, DKIM and DMARC: what each one actually does Three records, three different jobs. What each one proves, why DMARC needs the other two, and a rollout order that will not break delivery.
- HTTP security headers: which ones matter and what to set them to What each header actually defends against, a starting value for each, and how to ship a CSP without taking your own site down.
Guides are added when there is something worth saying, not on a schedule. If a result from one of the tools left you with a question these do not answer, that is useful to know — see the contact page.