Beyond Spam Filters: Using DMARC, SPF, and DKIM to Authenticate Your Business Emails

Relying only on spam filters isn’t enough anymore. While they can catch many suspicious messages, attackers have become skilled at bypassing them. This is where authentication protocols like DMARC, SPF, and DKIM step in.

What Is Email Authentication?

Email authentication is a set of protocols that verify whether an email message is sent from the domain it claims to represent. Without these checks, cybercriminals can spoof your domain, making their phishing emails look like they’re coming from you.

This reassures email providers like Google that your messages are trustworthy. More importantly, it stops bad actors from impersonating your business. 

Why Email Authentication Matters Now

Cybercrime through email is not slowing down. According to Validity’s DMARC Adoption Report, 84% of domains used in “From” email addresses don’t have a DMARC record, exposing them to spoofing. Similarly, Infosecurity-Magazine highlights that over 90% of the world’s top domains are vulnerable to email spoofing attacks.

The financial impact is also staggering. The HoxHunt Phishing Trends Report found that 64% of businesses experienced Business Email Compromise (BEC) attacks, with the average loss per incident at around $150,000. For small businesses, such a loss can severely limit their operations.

Beyond the financial hit, there’s the trust factor. When customers receive fake invoices or malware-laced emails appearing to come from your domain, it erodes confidence in your brand. Once trust is gone, winning it back can take years.

Email Authentication Protocols

SPF, DKIM, and DMARC each play a unique role in verifying sender legitimacy. They create a layered defense that reduces the risk of phishing attacks and boosts trust with customers and partners.

Sender Policy Framework (SPF)

It specifies which servers are authorized to send emails on your behalf. If a message comes from an unauthorized server, receiving mail servers can reject it or flag it as suspicious.

Make sure you keep your SPF record up to date, but avoid making it too long in order to stay within DNS lookup limits.

DomainKeys Identified Mail (DKIM)

This attaches a unique digital signature to every email you send. The signature is verified using cryptographic keys stored in your DNS records. If even one character in the message is altered, the signature check fails.

Consider using at least a 2048-bit DKIM key for stronger protection. Shorter keys are easier to crack. You can also rotate DKIM keys periodically, making it harder for attackers to exploit them.

DMARC 

DMARC builds on SPF and DKIM by adding policy enforcement and reporting. This means you can tell receiving mail servers what to do with unauthenticated messages. For instance, you can let them through, quarantine them, or reject them.

The best part is that you gain insight into who is sending emails on your behalf. This makes it easier to detect and stop fraud. And since raw DMARC reports can be complex, you may use DMARC reporting tools like Dmarcian or Valimail to simplify analysis. 

Strategic Measures to Strengthen Email Authentication

Combine SPF, DKIM, and DMARC

Using just one protocol isn’t enough. SPF can stop unauthorized servers, but it doesn’t protect the message contents. DKIM verifies integrity, but without DMARC, there’s no policy enforcement. 

When all three work together, they create a layered defense, protecting your brand from fraud. They also increases the likelihood of your emails landing in the inbox instead of the spam folder.

Gradual Enforcement 

Instead of immediately rejecting all emails that fail authentication, businesses can start with a “none” policy. This allows you to collect reports, analyze who is legitimately sending on your behalf, and identify SPF or DKIM configuration issues. This reduces the risk of accidentally blocking valid communications.

Once you’ve reviewed the reports and made adjustments, you can move to a “quarantine” policy, so you can flag suspicious emails and place them in the recipient’s spam folder. After ensuring all legitimate senders are authenticated, you can shift to a “reject” policy, fully blocking fraudulent messages. This strengthens security and prevents disruptions to genuine email traffic.

Update SPF Records

Outdated SPF records are a common reason why legitimate emails fail authentication. Your SPF record must therefore include all the services authorized to send emails on your behalf. This means if your business adopts new tools such as billing systems or cloud services, they should be added to the record.

Monitor Your Domain 

Attackers often register look-alike domains (e.g., using a zero instead of the letter “O”). These domains can be used to send phishing emails, host fake websites, or impersonate your brand. Regular domain monitoring can help identify unauthorized senders and potential vulnerabilities before they escalate. You can use tools like DomainTools to flag suspicious registrations in real time before they become full-scale attacks.

Create an Incident Response Plan

When a spoofing or phishing incident occurs, quick action is crucial. Have a documented plan that includes technical steps such as blocking domains and updating filters. You can also notify customers and outline procedures for escalating issues to IT providers and legal advisors. 

Set up Alerts

SPF, DKIM, and DMARC configurations are only effective when actively monitored. Cybercriminals test new ways to bypass defenses. Without oversight, issues can go undetected. Set up automated alerts tied to your DMARC reports or brand monitoring tools to ensure that any unauthorized sender is flagged. This allows you to respond quickly, minimizing the damage before attackers can exploit vulnerabilities.

Protect Your Reputation by Building a Safer Email Campaign 

Email impersonation doesn’t just cost money; it puts your reputation at risk. One successful phishing attack can make customers wary of opening any email from your brand. That hesitation can lead to lost revenue and weakened loyalty.

Spam filters still have their place, but they are no longer enough. Cybercriminals have grown more sophisticated, and businesses need stronger defenses. At Elliman Technologies, our team will help you set up DMARC, SPF, and DKIM and provide ongoing network monitoring so you can stay ahead of these threats.  

Book your free consultation today!