Email spoofing
Sending mail that falsely claims to come from someone else, usually by forging the From address with a domain the sender does not control.
What it means
SMTP lets the sender write any From address, so forging one takes no skill. Exact-domain spoofing uses the real domain itself (ceo@example.com sent by an outsider). Related tricks use a different domain that looks similar, or a misleading display name over an unrelated address.
SPF, DKIM and DMARC are the defence against exact-domain spoofing. With DMARC at quarantine or reject, receivers that honour it filter or refuse mail that uses the domain without passing aligned authentication. Microsoft 365 also runs its own spoof detection, treating a message as spoofed when it is confident the From address is forged.
Lookalike domains and display names pass straight through those checks, because the attacker authenticates a domain they own.
Related terms
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Sources
What this definition rests on. The wording is ours; the facts are theirs.
All 432 terms in the glossaryThe wiki: blocklists and bounce codes