Glossary · DNS
A CNAME record makes one hostname an alias of another, so lookups for it are answered with the target's records.
www.acme.com CNAME acme.netlify.app means “ask about that name instead”. Email services use CNAMEs to delegate DKIM keys and bounce domains, so they can rotate keys without you editing DNS.
A name with a CNAME can't have any other record, which is why the bare domain (the zone apex) can't be a CNAME: it needs NS and SOA records. Some DNS hosts offer flattening or ALIAS records to get around this. MX records must not point at a CNAME.
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