Why DMARC Matters: Protecting Your Brand From Business Email Compromise in Google Workspace

A senior accountant receives a message late on a Thursday afternoon. It’s short, professional, and marked Sent from my iPhone. The sender is the CEO and the request is urgent: a $45,000 vendor payment needed immediately to secure a confidential deal. The email appears completely legitimate and it comes from the company’s domain, lands directly in the Google Workspace inbox, and carries none of the usual external sender warnings.

Trusting the sender and pressured by urgency, the accountant processes the payment. By the next morning, the funds were gone and the CEO never even sent the email.

This is Business Email Compromise (BEC), which is one of the most financially devastating and deceptively simple cyberattacks facing organizations today. The attack is simple with no malware, no breached endpoints and no sophisticated exploits, just a convincingly forged identity. For organizations operating in Google Workspace, BEC exposes a harsh reality: if attackers can impersonate your domain, they can bypass human judgment and technical controls in a single message.

The Engine of Modern Business Email Compromise (BEC)

The Anatomy of an Exploit

Business Email Compromise has evolved from simple phishing into a mature, highly profitable criminal industry. Attackers no longer rely on “spray and pray” tactics; they conduct “Virtual Reconnissance”. They study organizational charts on LinkedIn, analyze the tone of executive blog posts, and identify the specific timing of financial quarters.

What makes BEC so effective in Google Workspace is the inherent trust built into the ecosystem. Internal emails move quickly, and collaboration is the default setting. When an email appears to originate from a trusted internal domain, the human brain’s “threat detection” is often bypassed.

The Scale of the Threat

According to the FBI’s Internet Crime Complaint Center (IC3), BEC accounts for billions of dollars in adjusted losses annually. It is more profitable than ransomware because it requires zero technical overhead, no servers to maintain, and no encryption keys to manage; only requires a spoofed email address and a convincing story.

The AI Catalyst (2025-2026)

In the current threat landscape, AI-generated BEC has become the primary concern. Attackers use Large Language Models (LLMs) to:

• Mimic Linguistic Fingerprints: They can mirror the specific syntax, greeting style, and even the “typos” characteristic of a specific CEO.
• Contextual Awareness: AI can synthesize news about a recent company merger to create a highly relevant and urgent narrative.
• Scale Impersonation: An attacker can launch 1,000 unique, personalized BEC attacks across different subsidiaries in the time it used to take to write one.

Technical Deep Dive: The Foundation of Email Trust

To stop these attacks, we must understand the “Triple Crown” of email authentication: SPF, DKIM, and DMARC.

SPF (Sender Policy Framework): The Guest List

SPF is a DNS record that lists the specific IP addresses and servers authorized to send email on behalf of your domain.

• Mechanics: When an email arrives, the receiving server looks at the “Envelope From” address and checks the DNS of that domain. If the sending IP isn’t on the list, it’s a failure.
• The Fragility of SPF: SPF is notoriously difficult to manage at scale. The 10-lookup limit is a hard ceiling. If your organization uses Google Workspace, plus Salesforce, plus Zendesk, plus HubSpot, you may exceed this limit, causing a “Permerror” and breaking your email delivery.

DKIM (DomainKeys Identified Mail): The Digital Signature

DKIM uses asymmetric cryptography to sign emails.

• Mechanics: Your outgoing mail server uses a private key to generate a signature for each email header. The receiving server uses the public key (published in your DNS) to verify it.
• The Blind Spot: DKIM proves that the message wasn’t changed and that it came from the domain that signed it. However, it doesn’t force that domain to match the one the user sees in the “From” field.

DMARC (Domain-based Message Authentication, Reporting, and Conformance)

DMARC is the policy layer that ties SPF and DKIM together. It solves the “Alignment” problem.

• Alignment: DMARC ensures that the domain in the “Header From” (the one the human sees) matches the domain validated by SPF or DKIM.
• Reporting: DMARC provides RUA (Aggregate) and RUF (Forensic) reports, giving Google Workspace admins a “God’s eye view” of every server in the world sending mail using their domain.

Deep Dive into DMARC Enforcement Stages

Transitioning to a secure DMARC posture is a tactical operation that requires precision.

1. Monitoring (p=none)

This is the data-gathering phase. You are telling the world: “I have DMARC, but don’t block anything yet; just send me the reports.”

• Strategy: Use this period to identify “Shadow IT.” You will likely discover marketing departments or regional offices using third-party email tools you didn’t know existed.
• Duration: Typically 4-8 weeks for a standard enterprise.

2. Quarantine (p=quarantine)

This is the “Soft Enforcement” phase. You tell the receiving servers: “If the email fails authentication, put it in the Spam folder.”

• Strategy: This allows you to test your configuration. If a critical business tool was missed in the audit, the email will still be “deliverable” (found in Spam) rather than lost forever.
• The Risk: In BEC attacks, a “quarantined” email can still be dangerous if an employee checks their spam folder and trusts the “internal” sender.

3. Reject (p=reject)

This is the Gold Standard of Google Workspace governance. You tell the world: “If it’s not authenticated, drop it. Do not deliver it.”

• The Impact: Exact-domain spoofing is effectively eradicated. An attacker cannot send an email that claims to be from your domain and have it land in any inbox on a modern mail provider.

Special Session with Billy McDiarmid (Red Sift)

To help our community navigate the complexities of these protocols, we hosted a session with Billy McDiarmid from Red Sift, one of the world’s leading experts on sender identity.

In this deep-dive webinar Billy explored:

• The BEC Anatomy: Why attackers impersonate executives and the psychological triggers they use to bypass standard filters.
• The Power of Three: How to align SPF, DKIM, and DMARC to create a “bulletproof” sender identity that protects your brand.
• Mandatory Authentication: Navigating the 2025-2026 requirements from Google and Yahoo. If you are a bulk sender and haven’t reached enforcement, your deliverability is at risk.
• The Path to p=reject: A practical, step-by-step guide on moving from monitoring to active enforcement without blocking legitimate business mail.
• Live Tools and Tactics: A demonstration of how to spot vulnerabilities in your DNS records before attackers do.

If you missed out on the session, why not catch up via our YouTube channel here. 

DMARC and the Global Regulatory Landscape

The 2025-2026 Mandates

Google and Yahoo have fundamentally changed the rules of the internet. As of late 2024 and moving into 2026, DMARC is no longer optional for anyone sending more than 5,000 emails a day.

• The Penalty: If you do not have a DMARC record, your emails will be flagged as “Unauthenticated,” potentially causing them to be suppressed or rejected entirely.
• The Benefit: Organizations with enforced DMARC (p=quarantine or p=reject) see an immediate increase in deliverability rates and better placement in the “Primary” tab of Gmail.

PCI DSS 4.0 and Beyond

For organizations handling credit card data, PCI DSS 4.0 now includes requirements for protecting against spoofing and phishing. DMARC is the most direct way to meet these compliance standards. By securing your email domain, you are checking off multiple boxes in your regulatory and insurance audits.

Strategic Governance in Google Workspace

Protecting Subdomains and Parked Domains

One of the most common mistakes in Google Workspace governance is only protecting the primary domain (e.g., company.com). Attackers know this and will often spoof subdomains like mail.company.com or dev.company.com.

• The Solution: DMARC policies should be applied to all subdomains using the sp=reject tag.
• Parked Domains: If your company owns company-deals.com but doesn’t use it, you must still publish a “deny-all” DMARC record to prevent attackers from using that “parked” real estate for phishing.

The Role of BIMI (Brand Indicators for Message Identification)

Once you reach p=reject, you unlock the ability to implement BIMI. This allows your official corporate logo to appear next to your emails in the Gmail inbox.

• The Trust Signal: In a world of AI-generated fraud, the BIMI logo is a visual confirmation of authenticity. It has been shown to increase email open rates by up to 10% because users feel safe interacting with the content.

The “Backdoor” of Google Drive and File Sharing

While DMARC handles the identity of the sender, the Google Workspace manager must also be concerned with what happens after the email is opened.

Attackers often use spoofed emails to lead users to malicious Google Drive links and because these notifications look like native Google system alerts, they are highly effective.

• The Risk of Public Links: Even with DMARC, if your internal file-sharing settings allow “Anyone with the link” access, an attacker who gains access to a single link can leak entire directories.
• Audit and Visibility: Admins must regularly audit “External Sharing” reports to ensure that sensitive folders are not being accessed by unauthorized domains.

Troubleshooting Common DMARC Failures

Even with the best intentions, DMARC implementation can hit snags.

1. The “Forwarding” Problem

When an email is forwarded (e.g., from a personal account to a work account), the SPF check will often fail because the forwarding server’s IP is not in your DNS record.

• The Solution: This is why DKIM is so important. DKIM signatures survive forwarding, allowing the email to stay “Aligned” and pass the DMARC check even when SPF fails.

2. Header Mismatch (Display Name Spoofing)

DMARC protects the domain, but it doesn’t protect the Display Name. An attacker could send from attacker@unknown-domain.com but set the display name to “Your CEO.”

• The Defense: Google Workspace has built-in protections for this, but DMARC is the foundational layer that ensures the “from” address itself cannot be spoofed.

Conclusion: A Culture of Verified Identity

The path to a secure Google Workspace environment is not built on a single piece of software, but on a strategy of verified identity.

Business Email Compromise is a threat that scales with the success of your brand. The more recognizable your brand becomes, the more valuable your domain name is to a criminal. By enforcing DMARC, auditing your third-party senders, and staying ahead of regulatory requirements, you are protecting the most valuable asset your company owns: its reputation.

The discussion surrounding DMARC has shifted. It is no longer a question of if you should implement it, but how quickly you can reach enforcement before an attacker finds the gap.

Your Next Step

Are you ready to stop being a “soft target” for BEC?

Catch up on our session with Billy McDiarmid to learn the advanced tactics for reaching DMARC enforcement and securing your Google Workspace domain for 2026.

Want to be ahead of the curve within your Google Workspace environment? Why not join our exclusive community to stay up to date with the latest updates and learn from IT admins and partners alike. Join the community here.