Point a domain at a new website

A web launch should be the least dangerous change on this list. It becomes dangerous when the hosting provider's setup guide is written for somebody with one domain and no mail.

# The apex problem

Static hosts and platforms often ask for a CNAME. A CNAME cannot exist at a zone apex alongside other records: RFC 1034 forbids it, and resolvers are entitled to ignore everything else at that name — including the MX. Some do, some do not, so mail becomes intermittent per-resolver, which is close to unfixable by argument.

• Use an A or AAAA record at the apex where the host publishes addresses.
• Use ALIAS/ANAME where your provider supports it — Cloudflare, DNSimple and others flatten it correctly.
• Or point the apex at a redirect and serve the site from www.

# The change

1. Lower TTLs on the web records A day ahead if the launch is planned. This is the only part of a web launch worth planning.
2. Change only the web records The apex A, the www record, and nothing else. MX, SPF, DKIM and DMARC are not part of a website change.
3. Check the results cname-not-at-apex and cname-must-not-coexist both block. If either fires, the hosting instruction was written for a simpler situation than yours.
4. Verify from outside And confirm the certificate on the new host covers both the apex and www before announcing it.