Definition
Header-From
The Header-From is the From field of the message header, meaning the only sender your recipient actually sees displayed in their mail client, and it is the identity DMARC protects.
Filling it in takes exactly as much technical skill as filling in the subject line. Neither SPF nor DKIM checks it on its own: SPF looks at the Envelope-From and DKIM looks at its own d=. It is DMARC, and only DMARC, that requires one of the two to match this field.
It also carries a display name, subject to no control whatsoever. “Finance Director <contact@unknown-supplier.com>” passes every technical check a correctly configured domain applies, because the impersonated domain is not in the address at all: it is in the label. No DNS record answers this attack; only your staff's attention does.
- Also known as
- From header, display From, RFC5322.From, friendly-from, visible sender
- Standard
- RFC 5322, §3.6.2