Header From
Learn what the Header From field is, how it affects DMARC alignment, and how DMARCeye detects spoofing through header domain analysis.
What is the Header From in email?
The Header From is the visible sender address that appears in the “From” field of an email message, as defined by RFC 5322. It represents the identity that users see when reading an email in their inbox, such as “From: support@example.com.” Unlike the envelope sender used in SMTP delivery, the Header From is part of the message’s header content rather than its transport envelope.
Because the Header From is visible to recipients, it carries strong trust implications. Attackers often exploit this field in spoofing or phishing attempts by forging legitimate-looking addresses to deceive users.
How Header From Works
The Header From field defines the author or sender of an email message. It may include both a display name and an email address, for example:
From: “DMARC Support” <support@example.com>Mail systems use this header to determine who the message appears to come from. In contrast, the “Return-Path” or “MAIL FROM” address identifies where bounce messages are sent. This distinction is critical for DMARC alignment checks, which compare the domain in the Header From against those used in SPF and DKIM.
Header From and DMARC Alignment
DMARC determines message legitimacy by ensuring that at least one authentication mechanism (SPF or DKIM) aligns with the domain shown in the Header From. If the message passes authentication but the domains do not match, DMARC fails the alignment check, signaling possible impersonation.
Best Practices
- Ensure that all legitimate senders use consistent Header From domains
- Avoid third-party senders using mismatched domains
- Regularly monitor DMARC aggregate reports for misalignments
- Educate users to verify the sender’s address before engaging with unexpected emails
Header From and DMARCeye
DMARCeye analyzes the Header From domain in all authentication reports to detect misalignment, unauthorized sending sources, and impersonation attempts. By comparing Header From data with SPF and DKIM results, DMARCeye identifies where domain identity is being spoofed or misused.
This analysis helps organizations maintain consistency between their visible sender identities and underlying authentication data, ensuring both trust and deliverability.
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To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.