Glossary · Authentication
Email spoofing is sending mail with a forged sender address, usually to impersonate a trusted company or person in phishing.
The email protocol lets the sender write any From address, so forging one takes no skill. What stops a forgery reaching the inbox is the receiving server checking authentication, and an enforced DMARC policy telling it to quarantine or reject mail that fails.
DMARC covers exact-domain spoofing only. Attackers also use lookalike domains (acme-billing.com, acrne.com) and display-name tricks (“Acme Support” <random@freemail>), which need user awareness and receiver-side filtering.
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