How to identify and prevent email spoofing on your domain

Email spoofing remains one of the most effective and dangerous attack vectors facing organizations today. In 2024, Business Email Compromise attacks cost organizations $2.7 billion in the US alone [1], with over 57% of phishing attacks sent from compromised email accounts [2]. For IT and security professionals, protecting your domain from spoofing attacks has never been more urgent.

Here's how to identify when attackers are impersonating your domain and implement robust prevention measures that actually work.

Required:

• Administrative access to your domain's DNS records
• Access to your email infrastructure (mail servers, third-party email services)
• Basic understanding of DNS record management

Helpful:

• Email security monitoring tools or DMARC reporting platform
• List of all authorized email sending services for your domain
• Access to email header information from your mail system

Time investment: Initial setup requires several hours. Ongoing monitoring requires regular weekly attention Skill Level: Intermediate (basic DNS knowledge required)

This guide walks you through a systematic approach to identify spoofing attempts targeting your domain and implement email authentication protocols that block unauthorized senders. We'll focus on practical, actionable steps that deliver measurable protection.

The 5-step process:

1. Audit your current email authentication status
2. Identify spoofing attempts and unauthorized senders
3. Configure SPF and DKIM authentication
4. Implement DMARC with proper monitoring
5. Achieve enforcement and maintain ongoing protection

Expected outcome: Complete visibility into who's sending email using your domain, with the ability to block unauthorized senders and prevent spoofing attacks.

What you're doing: Checking whether your domain has existing email authentication protocols and identifying gaps in your current setup.

How to do it:

1. Use an online DMARC checker tool to scan your domain's DNS records for SPF, DKIM, and DMARC entries
2. Document which protocols are already configured and their current policy settings
3. Identify all legitimate email-sending services your organization uses (marketing platforms, CRM systems, notification services, etc.)
4. Check if each sending service is properly authenticated with SPF and DKIM records
5. Review your domain's current email reputation using blacklist monitoring tools

Pro tip: Many organizations discover "shadow IT" during this audit: email-sending services that teams are using without the security team's knowledge. This is exactly the visibility you need before implementing stricter controls.

What success looks like: You have a complete inventory of all authorized sending sources and understand which authentication protocols are currently in place (if any).

Troubleshooting: If you can't identify all email-sending services, check with department heads about third-party tools they use. Marketing, HR, and customer success teams often use dedicated platforms that send email on your domain's behalf.

What you're doing: Learning how to spot when attackers are impersonating your domain and recognizing the warning signs of spoofing attacks.

How to do it:

1. Analyze email headers from suspicious messages claiming to be from your domain. Look for mismatched "Return-Path" and "From" fields
2. Check the "Received" lines in headers for originating IP addresses that don't match your authorized mail servers
3. Look for SPF, DKIM, or DMARC authentication failures in email headers (typically shown as "fail" or "softfail" results)
4. Monitor for reports from customers or partners receiving suspicious emails appearing to come from your domain
5. Review any existing DMARC reports (if you have monitoring configured) for failed authentication attempts

Pro tip: Email spoofing often spikes during tax season, holiday shopping periods, or major company announcements when attackers know people are expecting legitimate emails from brands. Monitor more closely during these high-risk periods.

What success looks like: You can confidently identify whether an email truly came from your domain or is a spoofed message, and you understand the volume and sources of unauthorized sending attempts.

Troubleshooting: If you're not receiving DMARC reports yet, you won't have historical data about spoofing attempts. You'll start collecting this data once DMARC is configured in the next steps.

What you're doing: Setting up the foundational email authentication protocols that verify your legitimate email sources.

How to do it:

1. Create or update your SPF record in DNS to include all authorized sending IP addresses and domains (format: v=spf1 include:_spf.example.com ~all)
2. Ensure your SPF record doesn't exceed the 10 DNS lookup limit (this is a common pitfall that breaks email deliverability), or work with a DMARC provider who can overcome this limit for you
3. Configure DKIM signing on your mail servers and email-sending services (each service typically provides specific DKIM configuration instructions)
4. Add DKIM public keys to your DNS records as TXT entries (format: selector._domainkey.yourdomain.com)
5. Test that SPF and DKIM are working correctly by sending test emails and checking authentication results in headers

Pro tip: SPF records are surprisingly easy to break. Organizations frequently exceed the 10 DNS lookup limit as they add more sending services. Red Sift OnDMARC's Dynamic SPF feature solves this by consolidating all authorized services into a single dynamic include that never exceeds the limit.

What success looks like: Test emails from all your authorized sending sources pass SPF and DKIM authentication checks. You can verify this in email headers or using authentication testing tools.

Troubleshooting: If legitimate emails start failing SPF checks after making changes, you likely have a syntax error in your SPF record or exceeded the lookup limit. Use an SPF validator tool to identify the specific issue. For complex email infrastructures with many sending services, consider using an automated SPF management solution.

What you're doing: Deploying DMARC to tell receiving mail servers how to handle emails that fail authentication, while collecting valuable intelligence about email traffic.

How to do it:

1. Create a DMARC record in DNS starting with a monitoring-only policy (format: v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com)
2. Set up a dedicated email address or reporting platform to receive DMARC aggregate reports (these XML files show authentication results for all email using your domain)
3. Monitor incoming DMARC reports during an initial observation period to identify any legitimate sending sources you missed in your initial audit
4. Verify that all authorized senders consistently pass SPF or DKIM authentication in the reports
5. Prepare to progressively tighten your DMARC policy from monitoring (p=none) to quarantine (p=quarantine) and eventually reject (p=reject)

Pro tip: DMARC reports are notoriously difficult to parse. They arrive as XML files that are nearly impossible to read without specialized tools. Red Sift OnDMARC automatically processes these reports and translates them into actionable intelligence, showing exactly which sources are passing or failing authentication and providing specific remediation steps.

What success looks like: You're receiving regular DMARC aggregate reports, you can identify the sending sources in those reports, and you've confirmed that all legitimate email passes authentication consistently.

Troubleshooting: If you're not receiving any DMARC reports, check that your RUA email address is correctly formatted in the DMARC record and that the mailbox isn't rejecting incoming reports. Some organizations use dedicated DMARC reporting services instead of managing reports via email.

Manual DMARC implementation can take organizations many months to reach full enforcement, with many getting stuck in monitoring mode indefinitely due to the complexity of managing authentication across multiple sending sources.

Red Sift OnDMARC helps organizations achieve full DMARC enforcement significantly faster than manual implementation. Here's what makes the difference:

• Dynamic Services: Manage SPF, DKIM, DMARC, and MTA-STS records directly from the OnDMARC interface without touching DNS, eliminating configuration errors and delays
• Intelligent Report Analysis: Transforms complex DMARC XML reports into clear, actionable insights showing exactly which sending sources need attention
• Guided Remediation: Provides specific instructions for fixing authentication failures, removing the guesswork from DMARC deployment
• DNS Guardian: Continuously monitors for subdomain misconfigurations and prevents "SubdoMailing" attacks that bypass DMARC
• Radar AI Assistant: Finds and resolves email security issues up to 10x faster using AI-powered analysis

When to consider Red Sift OnDMARC:

1. Your organization uses multiple email-sending services that need authentication coordination
2. You need to reach DMARC enforcement quickly to meet compliance requirements or security mandates
3. Your team lacks the specialized expertise required for complex DMARC management
4. You're experiencing SPF lookup limit issues that break email deliverability
5. You want continuous monitoring and automated alerts for email security threats

What you're doing: Progressively tightening your DMARC policy to actively block spoofed emails, completing your domain protection.

How to do it:

1. After confirming all legitimate email consistently passes authentication over a sufficient observation period, update your DMARC policy to quarantine (p=quarantine)
2. Monitor DMARC reports closely during the quarantine phase to catch any legitimate senders that may intermittently fail authentication
3. Resolve any authentication failures for legitimate senders before proceeding
4. Once you have 100% pass rates for authorized senders, update to reject policy (p=reject) for full enforcement
5. Set up automated monitoring and alerts to catch new authentication issues promptly

Pro tip: Don't rush to enforcement. Organizations that skip the monitoring phase often discover too late that they've blocked important business email. That said, don't get stuck in monitoring mode forever. Move toward enforcement once you've validated all legitimate sending sources.

What success looks like: Your DMARC policy is set to reject (p=reject), unauthorized emails using your domain are being blocked by receiving mail servers, and all legitimate business email continues to deliver successfully. You're receiving regular reports showing spoofed emails being rejected.

Troubleshooting: If legitimate email starts bouncing after moving to enforcement, temporarily revert to quarantine policy while you investigate. Check DMARC reports to identify which sending source is failing authentication and work with that service provider to fix their SPF or DKIM configuration.

• Why it happens: Organizations hear about DMARC mandates and rush to add a DMARC record without ensuring underlying authentication protocols are working
• How to avoid: Always configure and verify SPF and DKIM before adding DMARC
• If it happens: Your DMARC policy won't provide protection because all email will fail authentication. Go back and properly configure SPF and DKIM first

• Why it happens: Security teams want immediate protection and skip the monitoring and quarantine phases
• How to avoid: Follow the progressive enforcement approach (none → quarantine → reject) with sufficient monitoring time at each stage
• If it happens: Legitimate business email may be blocked. Immediately revert to monitoring policy and properly audit all sending sources

• Why it happens: Teams keep adding "include" statements to SPF records without counting DNS lookups
• How to avoid: Use an SPF validator to check lookup counts before publishing changes, or use Dynamic SPF solutions
• If it happens: Email deliverability breaks entirely. You'll need to consolidate your SPF record, use SPF flattening, or implement a managed SPF solution

• Why it happens: Teams treat DMARC as "set it and forget it" after reaching enforcement
• How to avoid: Set up automated monitoring and alerts for authentication failures
• If it happens: You won't notice when new sending services are deployed without proper authentication, potentially breaking legitimate email

Key indicators:

• 100% of legitimate email from your domain passes SPF or DKIM authentication
• Your DMARC policy is set to reject (p=reject), actively blocking spoofed emails
• DMARC reports show significantly fewer or zero unauthorized sending attempts
• Zero deliverability issues with legitimate business email
• Improved domain reputation and inbox placement rates

Once you've achieved DMARC enforcement, consider these additional protections:

Subdomain protection: Many attackers pivot to using subdomains when main domain spoofing is blocked. Configure DMARC records for key subdomains and use DNS monitoring tools to detect misconfigured or orphaned DNS records.

BIMI implementation: Once at p=reject enforcement, implement BIMI (Brand Indicators for Message Identification) to display your verified brand logo in supported email clients. Research shows BIMI can improve email open rates by helping emails stand out in inboxes and building trust with recipients through visual brand verification.

MTA-STS deployment: Add Mail Transfer Agent Strict Transport Security to enforce encrypted email delivery and prevent man-in-the-middle attacks on your email traffic.

Continuous threat monitoring: Use email security platforms that provide real-time alerts for domain spoofing attempts, lookalike domain registrations, and authentication anomalies.

Immediate actions:

• Run a DMARC check on your domain to understand your current authentication status
• Begin cataloging all email-sending services your organization uses
• Set up a plan to implement SPF, DKIM, and DMARC following the steps outlined above

Ongoing maintenance:

• Review DMARC reports weekly to monitor authentication health
• Update SPF and DKIM records whenever new sending services are added
• Monitor domain reputation and deliverability metrics monthly
• Conduct periodic audits to ensure authentication remains properly configured

Email spoofing represents a critical threat to your organization's security and reputation. The good news is that with proper email authentication protocols in place, you can effectively block unauthorized senders and protect your domain from impersonation attacks. Whether you choose manual implementation or an automated platform like Red Sift OnDMARC, the most important step is getting started today.

[1] Federal Bureau of Investigation. "Internet Crime Report 2024: Business Email Compromise Losses." DeepStrike. https://deepstrike.io/blog/Phishing-Statistics-2025

[2] KnowBe4. "Phishing Threat Trends Report 2025: Compromised Account Statistics." KnowBe4 Research, March 2025. https://www.knowbe4.com/hubfs/Phishing-Threat-Trends-2025_Report.pdf

[3] Fanelli, Bill P. "DMARC: The Frontline Defense Against Phishing and Domain Spoofing." Homeland Security Today, October 2025. https://www.hstoday.us/subject-matter-areas/cybersecurity/dmarc-the-frontline-defense-against-phishing-and-domain-spoofing/