Summary
When your domain experiences spoofing attempts that result in DKIM or SPF failures, the immediate concern is how to address these incidents and prevent future occurrences. While the failures themselves indicate that authentication protocols are working to some extent, further steps are often necessary to fully secure your domain and maintain email deliverability.This includes understanding the role of DMARC and distinguishing between malicious spoofing and legitimate but misconfigured sending. Proactive measures and continuous monitoring are key to minimizing impact on your sender reputation and ensuring your legitimate emails reach the inbox.
Key findings
- DMARC role: SPF and DKIM failures are typically managed by DMARC enforcement.
- Distinguish sources: It is crucial to differentiate between true spoofing and legitimate but misconfigured sending from your domain.
- Transient issues: Occasional, random failures of legitimate emails can stem from temporary DNS glitches or issues within the Email Service Provider's (ESP) infrastructure.
- Debugging causes: Debugging DMARC failures requires careful consideration of potential causes, including email gateways and a lack of DKIM for legitimate sources.
Key considerations
- Set DMARC policy: Configure your DMARC policy to quarantine or reject spoofed emails effectively.
- Analyze DMARC reports: Regularly review reports to identify the source of failed emails and differentiate between malicious and legitimate but misconfigured sending.
- Ensure authentication: Verify all legitimate sending sources are correctly configured with SPF and DKIM to prevent your own emails from failing authentication checks.
- Monitor anomalies: Keep an eye on your email logs and DMARC reports for sudden spikes in failures, which could indicate new spoofing attempts or system misconfigurations.
- Maintain DNS: Ensure your DNS records are stable and correctly propagated to minimize transient authentication failures. Random DNS glitches can cause temporary failures.A guide to SPF, DKIM, and DMARC.
What email marketers say
Email marketers often encounter challenges with email authentication, especially when dealing with spoofing attempts that trigger SPF and DKIM failures. Their primary concerns revolve around protecting brand reputation, ensuring legitimate emails reach the inbox, and understanding the nuances of DMARC reporting. They frequently seek clarity on how to differentiate between malicious actors and unintended internal misconfigurations.It's a common scenario where a spoofed email will fail these checks, but occasionally, a legitimate email might also fail, leading to confusion and potential deliverability issues.
Key opinions
- DMARC is key: DMARC enforcement is essential for identifying and managing spoofed emails that fail SPF and DKIM.
- Rogue applications: Marketers need to check if SPF/DKIM failures are genuine spoofing or an unauthenticated internal application.
- Fix legitimate: If a legitimate application is causing authentication failures, the primary step is to correctly configure its SPF and DKIM.
- Trust DMARC: If it's confirmed spoofing, allowing the DMARC policy to handle the failure is generally the correct approach.
- Random failures: It's not uncommon for a legitimate email to randomly fail authentication due to temporary DNS issues or other transient problems.
- Gateway impact: Email gateways (like Mimecast) can cause SPF and DKIM failures for automated emails.
- DKIM essential: Lacking DKIM can lead to MailFrom: rewrites by Office365 or Google.
- ESP infrastructure: Some issues are hard to pinpoint, relying on ESP infrastructure or DNS glitches.
Key considerations
- Authenticate all: Ensure every service sending emails on your behalf has correct SPF and DKIM setup.
- Consistent monitoring: Regularly review DMARC aggregate and forensic reports to catch patterns of spoofing or legitimate misconfigurations early.
- Prioritize systems: Focus on authenticating high-volume or critical email streams first to minimize impact if spoofing occurs.
- Report understanding: Familiarize yourself with the data in DMARC reports to quickly diagnose authentication issues.
- DNS stability: Work with IT or DNS providers to ensure stable and reliable DNS resolution for your SPF and DKIM records.
Marketer view
Marketer from Email Geeks states that DMARC enforcement is crucial for handling spoofing attempts. They find that checking DMARC reports helps identify issues where SPF and DKIM might be failing due to malicious activity.
Marketer view
Marketer from Email Geeks suggests determining if failing emails are actual spoofing or legitimate internal applications lacking proper authentication. They emphasize that distinguishing between these two scenarios is crucial for effective email deliverability management.
What the experts say
Experts in email deliverability and security emphasize that while SPF and DKIM failures due to spoofing indicate functional authentication, a holistic approach involving DMARC is paramount. They stress the importance of distinguishing between actual malicious spoofing and legitimate email flows that might be misconfigured, and they provide deeper insights into the complexities of email gateways and various mail service providers' handling of authentication.Their guidance often includes strategies for robust DMARC implementation and continuous monitoring to ensure domain integrity and optimal deliverability.
Key opinions
- Beyond basics: Simply having SPF and DKIM failures for spoofed emails is not enough; DMARC is essential for enforcement and reporting.
- Root cause: It's critical to ascertain whether authentication failures stem from malicious spoofing or from legitimate but improperly configured sending systems.
- Gateway effects: Email gateways (like Mimecast or Proofpoint) can inadvertently cause SPF and DKIM failures for legitimate, automated outgoing emails.
- DKIM critical: Relying solely on SPF can be problematic, as services like Office365 or Google might rewrite the MailFrom: header, leading to issues without DKIM alignment.
- Transient issues: Experts acknowledge that occasional legitimate email authentication failures are common due to DNS glitches or ESP infrastructure quirks.
Key considerations
- Full DMARC policy: Implement a DMARC policy beyond to or to gain control over spoofed emails.
- Report analysis: Utilize DMARC aggregate and forensic reports to precisely identify the source and nature of authentication failures.
- Sender audit: Continuously audit all services sending email on behalf of your domain to ensure they are properly authenticated with both SPF and DKIM.
- Vendor nuances: Be aware that different ESPs (e.g., Google, Microsoft) may handle MailFrom: headers or authentication differently, which can affect deliverability.How SPF, DKIM and DMARC work together.
- Proactive monitoring: Implement robust monitoring for your authentication records to detect misconfigurations or suspicious activity quickly.
Expert view
Expert from Word to the Wise suggests that proper SPF and DKIM configuration is the foundation. They highlight that DMARC acts as the policy layer that enforces specific actions against email spoofing attempts.
Expert view
Expert from Spam Resource highlights that distinguishing between genuine spoofing and misconfigured legitimate senders is the first step in effective mitigation. They advise this distinction helps focus remediation efforts correctly.
What the documentation says
Official documentation on email authentication protocols like SPF, DKIM, and DMARC consistently outlines the technical specifications and recommended practices for securing email domains against spoofing. These resources emphasize the layered security provided by these protocols and the importance of proper configuration, alignment, and policy enforcement to ensure legitimate emails are delivered while fraudulent ones are blocklisted or quarantined.Understanding these foundational principles is crucial for anyone managing email deliverability and security.
Key findings
- Layered security: SPF, DKIM, and DMARC work together to provide a robust framework for email authentication and anti-spoofing measures.
- SPF functionality: SPF allows domain owners to publish authorized sending IP addresses, helping receivers verify if an email originates from an approved server.
- DKIM functionality: DKIM provides a cryptographic signature that verifies the sender's identity and ensures the email content has not been tampered with.
- DMARC enforcement: DMARC (Domain-based Message Authentication, Reporting & Conformance) specifies how receiving mail servers should handle emails that fail SPF or DKIM validation.
- Alignment crucial: For DMARC to pass, either SPF or DKIM (or both) must align with the "From" domain in the email header.
Key considerations
- DMARC policy application: Documentation often recommends starting with a policy to gather data via DMARC reports before moving to or .
- Correct DNS records: Accurate and up-to-date DNS TXT records for SPF and DKIM are fundamental for successful email authentication.
- Sender authorization: All legitimate sending services must be explicitly authorized within your SPF record and correctly sign emails with DKIM.
- DMARC reporting analysis: Utilizing DMARC aggregate (RUA) and forensic (RUF) reports is key to understanding authentication failures and sources of spoofing.
- Domain reputation impact: Consistent SPF/DKIM failures, even for spoofed mail, can negatively impact your domain's reputation if DMARC isn't properly enforced. Refer to understanding how to fix SPF failure.
Technical article
Documentation from TechTarget explains that DMARC builds upon SPF and DKIM to provide a policy framework for email authentication. This framework allows domain owners to instruct receiving servers on how to handle messages that fail validation, offering crucial control.
Technical article
Documentation from Cloudflare states that DMARC is essential for preventing email spoofing and phishing. It achieves this by instructing mail servers on how to handle emails that do not pass SPF and DKIM checks, enhancing overall security.
Related resources
12 resources
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