SPF, DKIM, DMARC, MX
Fetch and parse SPF (Sender Policy Framework) records for a domain to validate email security.
Verify DKIM DNS records. Domain + selector → TXT lookup and parse.
Verify DMARC DNS records. Policy, RUA, RUF, alignment.
Check mail server (MX) records. Priority order.
Validate email format and check MX records. Verify if domain accepts mail.