What is the primary difference between DKIM authentication and DKIM alignment?

DKIM authentication verifies the email's signature against a public key, ensuring message integrity. DKIM alignment, on the other hand, checks if the signing domain (from the d= tag) matches the From header domain, which is crucial for DMARC to pass.

Why do some tools report DKIM as passing while others show it failing?

Different tools have varying levels of detail in their reports. Some only confirm a valid DKIM signature (authentication pass), while others perform the DMARC-required alignment check, which can fail even if authentication passes. The way tools interpret and display results for SPF alignment can also be inconsistent .

What is the best way to verify actual DKIM alignment status?

The most reliable method is to examine the raw Authentication-Results header of a received email. It provides detailed outcomes for SPF, DKIM, and DMARC, including the d= domain used for DKIM signing.

How can I fix DKIM alignment issues if my email service provider signs with a different domain?

If your ESP signs with their domain, you'll need to configure custom DKIM settings to sign with your own domain or a subdomain that aligns with your From address. This often involves adding a CNAME record to delegate signing authority to your ESP, enabling domain alignment best practices .

Does a DKIM alignment failure mean my emails won't be delivered?

Not necessarily. DKIM alignment failures mainly impact DMARC, which in turn affects deliverability based on your DMARC policy (e.g., p=none, p=quarantine, or p=reject ). Emails might still be delivered, especially with a p=none policy, but your domain's reputation and trust could be negatively impacted over time. A failing DKIM alignment is a common reason emails go to spam .

Why are DKIM alignment results inconsistent across tools and email headers? - DMARC - Email authentication - Knowledge base

It can be confusing when different email authentication tools and even raw email headers present conflicting results for DKIM alignment. You might see a pass for DKIM in one tool, like Google Postmaster Tools, but a fail in another, such as aboutmy.email or directly within the email's authentication results header. This inconsistency is a common challenge for those managing email deliverability, especially when you are just starting out. It signals that while the DKIM signature itself might be technically valid, there could be nuances in how different systems interpret or apply the alignment check required for DMARC.

Understanding these discrepancies requires a closer look at what DKIM alignment truly means and how various email platforms and tools evaluate it. DKIM, or DomainKeys Identified Mail, is a method designed to detect email spoofing. It allows the receiver to check that an email claiming to come from a specific domain was authorized by the owner of that domain. This is achieved by cryptographically signing the email using a private key and publishing a corresponding public key in the sender's DNS records.

The core of the issue often lies in how DKIM authentication interacts with DMARC (Domain-based Message Authentication, Reporting, and Conformance). For DMARC to pass, either SPF or DKIM (or both) must not only authenticate, but also align with the From domain. This alignment check is where many of the inconsistencies begin to show up. A tool might report DKIM as authenticated (meaning the signature is valid), but not necessarily aligned (meaning the signing domain matches the From domain correctly). Suped helps clarify these complex authentication flows through its easy-to-understand DMARC reports.

Understanding DKIM and alignment

DKIM alignment refers to the relationship between the domain in the From header of an email (the one users see) and the domain identified by DKIM. Specifically, it involves the d= tag in the DKIM-Signature header, which specifies the signing domain. For DMARC to pass, these domains must align. There are two types of DKIM alignment:

Relaxed alignment: Allows the From domain and the d= domain to be subdomains of each other. For instance, email.example.com aligns with example.com.
Strict alignment: Requires an exact match between the From domain and the d= domain.

The problem often arises when the email service provider (ESP) or mail transfer agent (MTA) you are using signs your emails with a domain different from your From address, even if the signature itself is valid. For example, if you send email through thirdparty.com but your From address is yourdomain.com, the DKIM

d= domain might be thirdparty.com. This leads to a DKIM authentication pass but an alignment failure. Understanding how to troubleshoot DKIM failures is crucial in these scenarios.

Why discrepancies occur

Several factors contribute to varying DKIM alignment results across different tools. One major reason is the difference in how each tool or platform processes and displays authentication information. Some tools might simply report whether a valid DKIM signature exists, while others go a step further to check for alignment with the From header domain, which is critical for DMARC. This can lead to situations where DMARC records pass in email headers but fail in validation tools.

Authentication Pass: The email has a valid DKIM signature that can be verified against the public key in DNS. This means the message hasn't been tampered with in transit.

Example: An email service signs mail for yourdomain.com using espsigning.net for d=. Authentication passes because the signature is valid for espsigning.net.

Alignment Fail: The domain in the From header does not match the d= domain in the DKIM signature according to DMARC's alignment rules (strict or relaxed).

Example: The From domain is yourdomain.com, but the DKIM d= domain is espsigning.net. This constitutes a DMARC alignment failure, even if DKIM authenticates.

Some tools, like Google Postmaster Tools, provide a high-level overview of deliverability metrics, including DKIM authentication rates, but might not always delve into the granular details of alignment that are visible in raw headers or more specialized tools. This is partly why email deliverability tools and Postmaster tools report conflicting authentication results. Other factors, such as OpenDKIM incorrectly validating DKIM signatures for emails with long headers, can also introduce discrepancies.

Some DMARC reporting tools, however, provide precise details about both DKIM authentication and alignment. Suped, for instance, offers granular DMARC reports that break down results by domain, showing exactly which emails are passing or failing DKIM alignment and why. This level of detail is critical for diagnosing subtle configuration issues that might be missed by aggregated reports.

Troubleshooting inconsistent DKIM alignment

To effectively troubleshoot inconsistent DKIM alignment, you need to examine the raw email headers. This is the most authoritative source of truth for how a receiving mail server processed your email. Look for the Authentication-Results header, which will contain detailed information about SPF, DKIM, and DMARC checks. For DKIM, you'll see a result like dkim=pass or dkim=fail, along with the header.d= value indicating the signing domain. Compare this d= domain with your From domain to determine the alignment status. Suped provides detailed DMARC reports from Google and Yahoo that can help you understand these nuances.

When checking email headers, look for the dkim= and

d= values in the Authentication-Results header to diagnose the exact issue. If dkim=pass but the d= domain doesn't align with your From domain, that's an alignment issue. If dkim=fail

, there's a problem with the signature itself, perhaps due to an incorrect key or message alteration.

If you're using a service like Gmail with a selector like s=google, ensure that your public key is correctly configured in DNS and that the Start signing or complete setup option has been clicked within your Google Workspace admin settings. A common pitfall is setting up the DNS record but forgetting to activate the signing process within Google's interface. This can lead to issues like Gmail SPF/DKIM issues and other validation tool conflicts.

For ongoing monitoring and to prevent these inconsistencies from impacting your deliverability, a robust DMARC monitoring tool is essential. Suped offers AI-powered recommendations to help you fix issues and strengthen your policy, real-time alerts for immediate issue detection, and a unified platform for DMARC, SPF, and DKIM monitoring. It also includes SPF flattening, which is critical for solving the SPF 10-lookup limit.

Resolving alignment issues

The key to resolving these inconsistencies is to systematically review each component of your DKIM setup and DMARC policy. Start by verifying your DKIM DNS record. Ensure the selector, domain, and public key are precisely what your email service provider (ESP) expects. Even a small typo or an extra space can invalidate the signature. Then, move on to checking the configurations within your ESP, confirming that DKIM signing is enabled and correctly associated with your sending domain.

Example of a DKIM record in DNSDNS

s1._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC3K6+l..."

Next, pay close attention to your DMARC record. The aspf and adkim tags in your DMARC policy dictate the required alignment mode (relaxed or strict). If your DKIM alignment is failing, consider whether a relaxed alignment policy could still satisfy your DMARC requirements, especially if your sending infrastructure uses subdomains for signing. For specific details on how to set up, you can refer to DKIM signature validation failures.

Tools like Suped simplify this process significantly by providing clear DMARC reports, including aggregated (RUA) and forensic (RUF) reports. These reports offer actionable insights and AI-powered recommendations to help you identify the root cause of DKIM alignment issues and implement the necessary fixes. This allows you to achieve a stronger DMARC policy and ensure your emails are consistently delivered to the inbox. Without proper DMARC monitoring, diagnosing these issues can be like searching for a needle in a haystack, especially when some emails are failing DMARC checks despite seemingly correct SPF and DKIM.

Views from the trenches

Best practices

Always check raw email headers for the definitive truth on DKIM authentication and alignment results.

Verify that your public key is correctly published in DNS and that your ESP has activated DKIM signing.

Use a DMARC monitoring tool like Suped to get a clear, consolidated view of all authentication results.

Test emails to various providers (like personal Gmail accounts) and inspect the `Authentication-Results` header.

Common pitfalls

Relying solely on high-level reports from Postmaster tools without deep-diving into granular alignment details.

Forgetting to activate DKIM signing in your email service provider's interface after publishing the DNS record.

Mismatch between the `d=` tag in the DKIM signature and the `From` header domain, causing DMARC alignment failures.

Not understanding the difference between DKIM authentication passing and DKIM alignment passing for DMARC.

Expert tips

Double-check for any hidden characters or formatting issues in your DKIM DNS record that might invalidate it.

Consider relaxed DKIM alignment if your sending infrastructure uses subdomains and strict alignment causes failures.

Implement DMARC gradually, starting with a `p=none` policy to gather data before moving to quarantine or reject.

Continuously monitor DMARC reports for changes in authentication or alignment status over time.

Expert view

Expert from Email Geeks says that if Gmail reports DKIM as signed, then any other tool showing a failure for DKIM alignment is likely experiencing a bug in its validation process.

2024-10-08 - Email Geeks

Expert view

Expert from Email Geeks mentioned sending an email to a personal Gmail account and examining the `Authentication-Results` header for more detailed failure information.

2024-10-08 - Email Geeks

Taking control of your DKIM alignment

Navigating the complexities of DKIM alignment and inconsistent reporting across various tools can be challenging, but a methodical approach to troubleshooting will help. Always prioritize the raw email headers for the most accurate authentication results and use comprehensive DMARC monitoring solutions to gain a clear, actionable overview.

Suped provides the tools and insights necessary to cut through the confusion, offering AI-powered recommendations and real-time alerts. This ensures your DKIM and DMARC configurations are not just authenticated, but also correctly aligned, safeguarding your email deliverability and brand reputation. With a focus on simplicity and powerful features, Suped makes DMARC management accessible for everyone.