What is Domain-based Message Authentication, Reporting, and Conformance (DMARC)?
Domain-based Message Authentication, Reporting, and Conformance (DMARC) is an email authentication, policy, and reporting protocol. It’s designed to protect email account owners from unauthorized use.
DMARC was created to combat email spoofing. This form of cyber attack involves using scripts to forge the fields that an email recipient sees. For example, the “from” or “reply-to” address. Since the spoofed email appears to be from a legitimate source, the recipient will likely click on a link or provide sensitive information.
Early mechanisms, such as SPF or DKIM, couldn’t combat this issue. So, in 2006, a consortium of industry leaders, including Google, Microsoft, and Yahoo, collaborated to create a standard that would empower domain owners with greater control over how their domains are used in email communications.
How does DMARC work?
DMARC adds a cryptographic signature to emails. This links the sender’s domain name with the email message, ensuring that the sender’s identity is authenticated through SPF or DKIM mechanisms.
It works as follows:
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Policy Declaration
Domain owners use DMARC records in DNS to state their email authentication policy, specifying the desired action for messages that do not pass authentication checks.
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Alignment Checks:
DMARC verifies that the domain in the SPF and DKIM records matches the domain in the “From” email address, ensuring consistency and authenticity.
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Reporting Mechanism:
DMARC provides feedback to the sending domain about messages that pass or fail DMARC evaluation, allowing domain owners to monitor and adjust their email authentication strategies.
There are three primary policy options:
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Reject:
Emails failing authentication are discarded.
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Quarantine:
Suspicious emails are placed in a holding area for further review.
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None (Report Only):
The receiver continues normal processing but sends reports to the domain owner about authentication results.
DMARC also allows senders to request reports from receivers detailing email authentication results. These reports provide valuable insights into email spoofing attempts and help identify unauthorized use of a domain.
DMARC in 2024:
In 2024, DMARC remains a critical tool for email security. Phishing attacks and email fraud continue to pose significant threats to individuals and organizations. DMARC adoption has grown steadily, with many leading email providers implementing DMARC by default for their customers.
This widespread adoption strengthens the overall email ecosystem by making it more difficult for cybercriminals to exploit email spoofing.