Emails are a crucial part of our daily lives, but how can we be sure that the emails we receive are genuinely from who they claim to be? That’s where DMARC comes in. But what is DMARC, and how does it work? Let’s break it down into simple terms.
What DMARC Aims to Do
DMARC, or Domain-based Message Authentication, Reporting, and Conformance, has several key goals:
- It allows the people who own a domain (like ‘example.com’) to tell email receivers what to do if an email claiming to be from their domain fails certain checks.
- It lets domain owners check if their email setup is working correctly.
- It aims to be easy to implement for both senders and receivers and to minimize any impact on the delivery of legitimate emails.
- It aims to reduce the amount of fake email that successfully gets delivered.
- It’s designed to work on a large scale, across the entire internet.
What DMARC Doesn’t Do
There are also several things that DMARC doesn’t try to do:
- It doesn’t treat unauthenticated emails differently from those that fail authentication.
- It doesn’t evaluate anything other than the ‘From’ address in the email.
- It doesn’t support multiple reporting formats or ways of publishing policies other than via the DNS (the internet’s address book).
- It doesn’t evaluate anything other than the last IP address that handled the email.
- It doesn’t deal with attacks on the ‘From’ field, also known as ‘display name’ attacks.
- It doesn’t authenticate anything other than domains, as it’s built on top of SPF and DKIM, which authenticate domains.
- It doesn’t analyze the content of emails.
How DMARC Scales
One of the big challenges for any system that works with email is scalability – it needs to work with the billions of emails that are sent every day. DMARC is designed to avoid the need for agreements between senders and receivers or third parties, which helps it to scale. However, it doesn’t prevent third parties from providing services that work with DMARC.
DMARC and Anti-Phishing
One of the main reasons for developing DMARC was to prevent ‘bad actors’ from sending emails that pretend to be from legitimate senders. This is often used in ‘phishing’ attacks, where the attacker tries to trick the recipient into revealing sensitive information. DMARC helps to combat this by making it harder for attackers to send emails that appear to be from a legitimate domain.
However, DMARC can’t solve all problems with fake or fraudulent emails. It doesn’t deal with attacks that use similar-looking domain names or abuse the ‘From’ name in the email. But despite these limitations, DMARC is a significant step forward in making email more secure.
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