Do subdomains inherit root domain authentication automatically?

Myth: False. Subdomains do not automatically inherit root domain authentication. Each subdomain needs its own SPF record if sending mail. DKIM requires selectors published for each sending subdomain.

DMARC has inheritance options: subdomain policy (sp=) can specify handling for subdomains, and subdomains without their own DMARC fall back to organizational domain policy.

Configure authentication explicitly for each sending subdomain rather than assuming inheritance. Test each subdomain independently to verify proper authentication.