Email Security Intelligence - DMARC Quarantine vs. Reject: Which Should You Implement to Secure Business Email against Sender Fraud?

In this era of heightened cyber risk, how can you verify the legitimacy of the emails you receive to avoid disclosing sensitive information or downloading ransomware? Phishing attacks have evolved to become so targeted and stealthy that, without the proper protocols and technology in place, even the most educated and aware users can fall for a scam - putting their organization’s key assets and reputation at great risk.

The use of the DMARC (Domain-based Message Authentication, Reporting, and Conformance) anti-phishing and anti-spoofing protocol can eliminate this uncertainty and mitigate this risk. However, in order to be effective, DMARC must be implemented properly and securely as part of a comprehensive email security strategy to safeguard the inbox against fraudulent emails that frequently lead to data theft, extensive downtime, fraudulent wire transfers and severe, lasting reputational harm. This article will explore whether you should implement DMARC Quarantine or DMARC Reject, and how DMARC can be set up and used most efficiently and effectively to protect against sender fraud and spoofing attacks.

What Is Email Spoofing & Why Is It A Threat to the Inbox?

Email spoofing is a tactic frequently used in phishing attacks and other email scams that involves a malicious actor sending an email with a fraudulent “From” address. In a spoofing attack, the sender forges an email header so that the client software displays the fraudulent sender address - which most users take at face value. By posing as someone that the recipient knows and trusts, cyber criminals are often able to trick users into sharing sensitive information, as recipients are more likely to click on a malicious URL, disclose credentials, install malware or wire corporate funds when it appears as if an email is from a friend or a colleague. Having an effective, multi-layered strategy in place that includes the use of the DMARC email authentication protocol to ensure that only legitimate mail reaches the inbox is critical in safeguarding users and key business assets against cyberattacks and breaches.

Implementing a p=quarantine DMARC Policy

Implementing a DMARC Quarantine policy informs participating receivers that you suggest they approach mail that fails the DMARC authentication check with extra caution. With a p=quarantine policy in place, messages that fail the DMARC authentication will still be accepted by the receiver, who is responsible for determining how they would like to implement the quarantine policy. Typically, non-compliant messages will be delivered to the receiver’s quarantine mailbox or spam folder, where they can then determine whether these emails are moved to the inbox or discarded.

DMARC Quarantine can be a great testing policy, as it allows companies to transition slowly and cautiously into using a stricter DMARC policy, giving them the opportunity to check that the right emails are passing and the wrong emails are failing. That being said, implementing a DMARC Quarantine policy must not be taken lightly, as receivers will begin to associate your domain with the junk emails if legitimate email is being quarantined or marked as spam - ultimately harming your reputation.

Implementing a p=reject DMARC Policy

Setting a p=reject DMARC policy is an even stricter safeguard against sender forgery attacks than a p=quarantine policy, ensuring that all malicious mail never reaches the receiver. With a DMARC Reject policy in place, the intended recipient will never know about non-compliant emails, as these emails are completely blocked. Thus, with a p=reject policy in place, users cannot be tricked into clicking on a malicious URL in a phishing email and disclosing sensitive credentials, or downloading ransomware via a malicious attachment.

The one drawback of implementing a DMARC Reject policy is that if legitimate emails are failing authentication and getting rejected, the receiver will never know about these emails. For organizations that are not actively using a reporting system to monitor authentication, it could take months to find out that legitimate email is not being delivered and remedy the issue - potentially interfering with marketing campaigns and interaction with current or potential customers.

How To Get the Most Out of DMARC Email Authentication - with the Least Amount of Risk

DMARC is a powerful email authentication method that is most effective in protecting against spoofing and sender fraud when it is implemented as part of a multi-layered email security solution managed by a provider with an in-depth understanding of these threats and how this protocol can best incorporated as part of a defense-in-depth approach to preventing email fraud and securing sensitive information.  Setting up DMARC is no easy feat and has the potential to undermine the success of your business if done so incorrectly. Partnering with an email security provider who assumes this responsibility can be greatly beneficial in terms of saving time, enhancing security and avoiding costly pitfalls.

Should you decide to implement DMARC on your own, the policy you choose is ultimately a decision that should be made with careful consideration of your organization's security needs and business requirements. At Guardian Digital, we generally recommend implementing a p=reject policy to ensure complete protection for the recipients of your emails. However, bear in mind that both p=quarantine and p=reject offer a significantly greater level of protection than p=none.

Guardian Digital EnGarde Cloud Email Security, a comprehensive, fully-managed email security solution, takes the complexity and risk out of implementing DMARC to help secure business email. EnGarde implements DMARC to the fullest to effectively and conveniently secure your users, your key business assets and your hard-earned reputation against phishing, ransomware, and other malicious attacks that frequently leverage spoofing and sender fraud. 

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