--- title: "10 Reasons Why DKIM Fails | DMARC Report" description: "DomainKeys Identified Mail (DKIM) is a digital authentication system used to verify the origin of email messages." image: "https://dmarcreport.com/og/blog/10-reasons-why-dkim-fails.png" canonical: "https://dmarcreport.com/blog/10-reasons-why-dkim-fails/" --- Quick Answer DomainKeys Identified Mail (DKIM) is a digital authentication system used to verify the origin of email messages. DKIM protects email receivers from spam and phishing scams through email spoofing. When using DKIM, the receiver can confirm that the message was sent by the domain listed in the DKIM signature. If DKIM fails, the email receiver will not be able to verify the origin of the message and may mark the message as spam or a phishing attempt. Related: [Free DKIM Lookup](/tools/dkim-lookup/) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2F10-reasons-why-dkim-fails%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=10%20Reasons%20Why%20DKIM%20Fails&url=undefined%2Fblog%2F10-reasons-why-dkim-fails%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2F10-reasons-why-dkim-fails%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2F10-reasons-why-dkim-fails%2F&title=10%20Reasons%20Why%20DKIM%20Fails "Share on Reddit") [ ](mailto:?subject=10%20Reasons%20Why%20DKIM%20Fails&body=Check out this article: undefined%2Fblog%2F10-reasons-why-dkim-fails%2F "Share via Email") ![10 Reasons Why DKIM Fails](https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-alignment-6379.jpg) ## Try Our Free DKIM Lookup Auto-discover DKIM selectors for any domain - scan 185 common selectors across all major providers. [ Discover DKIM Selectors → ](/tools/dkim-lookup/) DKIM ([RFC 6376](https://datatracker.ietf.org/doc/html/rfc6376)) signs email messages cryptographically, and unlike SPF, the signature survives email forwarding - which is why DMARC alignment via DKIM is more reliable than SPF alignment for forwarded mail. DomainKeys Identified Mail (DKIM) is a digital authentication system used to verify the origin of email messages. DKIM protects email receivers from spam and phishing scams through email spoofing. When using DKIM, the receiver can confirm that the message was sent by the domain listed in the DKIM signature. If \*\*DKIM fails, the email receiver will not be able to verify the origin of the message and may mark the message as spam or a phishing attempt. > The organizations that invest in email authentication early save themselves from expensive incidents later, says Vasile Diaconu, Operations Lead at DuoCircle. We see the pattern constantly: a domain gets spoofed, customers lose trust, and the remediation effort costs 10x what proactive DMARC setup would have cost. ## Why Does DKIM Fail? There are several reasons why DKIM can fail. Anything can go wrong with the DNS record that can prevent DKIM from working correctly. For example, if the DKIM-Signature record is not included in the DNS or is not formatted correctly, _DKIM will not work_. Below are the top ten reasons for DKIM failure: ## DNS Records Aren’t Set Up Properly DomainKeys Identified Mail (DKIM) is a way to _verify the identity of the sender of an email_ by adding a signature to the email that is cryptographically linked to the domain name from which the email was sent. However, DKIM can fail if the DNS records aren’t set up correctly. For DKIM to work, the DNS record for the sending domain must include a unique “DKIM-Signature” record. ![Dmarc record](https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-record-6071.jpg) ## Incorrect Sender ID The Sender ID checker uses the SPF record to determine if the message is spoofed. If the email doesn’t have an SPF record, or if the SPF record doesn’t include the sender’s domain, the Sender ID checker returns a **failure**. Therefore, your sender’s domain must be present in the SPF record to prevent the DKIM from failing because of an incorrect Sender ID. ## The Message Has Got Tampered or Contents Altered A typical attack against DKIM is to tamper with the message to invalidate the signature. It can happen when anyone changes the content or removes or adds headers. If the attacker can get the message to pass through the verification process, they can successfully _spoof the sender’s identity_. Therefore, it is essential to use a strong DKIM signature and carefully check the message for any changes to prevent such an occurrence. ## Invalid Signature One of the top reasons DKIM fails is an invalid signature. The email will not be authenticated with an invalid signature. To prevent this error, check the signature validity before sending the email. ## Key Management Another top reason DKIM fails is the key management. If the keys are not managed correctly, the email will not be authenticated. To prevent this situation, handle the keys correctly and keep them updated. ## Unauthorized Sender If the sender is not authorized, the email will **not get authenticated**. Ensure that emails are from trusted senders as per the records to prevent this error. ## Invalid Domain The domain name used in the DKIM signature must be valid and resolvable. If the domain is invalid or not configured correctly, the DKIM signature will not work, and the email will not pass authentication. ## Invalid Signing Key A common reason for DKIM failure is an invalid signing key. The key must be of the right type (RSA) and have the correct length. You must also store it in the correct location. i.e., the _private key should be stored on the server_, and the public key should be published in the DNS. If any one of the conditions is not met, DKIM will fail. It is essential to ensure that the signing key is set up correctly to prevent it. You should generate the key using a robust algorithm and store it in a secure location. Never share the private key with anyone other than the person responsible for signing email messages. ## Failed DNS Lookups ![Dmarc record generator](https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-record-generator-6079.jpg) Despite being a widely used email authentication standard, DKIM is not without its flaws. One of the most common problems is failed DNS lookups, preventing the DKIM signature from getting verified. Several factors can cause this situation, including **errors in DNS configuration**, temporary network outages, and malicious attacks. One way to help prevent failed DNS lookups is to use a third-party DNS service. These services offer easy-to-use tools that help you manage your DNS queries. ## Sender Policy Mismatch If the SPF records for a domain claim that a mail server can only send emails from a specific IP address range, but a message is sent from a different IP address, the DKIM signature for that message will fail. To prevent this occurrence, make sure your [SPF record](https://dmarcreport.com/blog/fix-spf-permerror-overcome-too-many-dns-lookups/) correctly identifies all the mail servers allowed to dispatch email on behalf of your domain. ## Final Words DKIM is an integral part of email authentication and helps [prevent spoofing](https://dmarcreport.com/what-is-dmarc/) and phishing. However, it is not infallible and can sometimes fail. The above discussion showed the top 10 reasons why DKIM might not work correctly for your email messages. You must have a thorough understanding and awareness of such situations and take precautions to avoid such errors for DKIM to function as intended. ## Topics [ DKIM ](/tags/dkim/) ![Brad Slavin](https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg) [ Brad Slavin ](/authors/brad-slavin/) General Manager Founder and General Manager of DuoCircle. Product strategy and commercial lead for DMARC Report's 2,000+ customer base. [LinkedIn Profile →](https://www.linkedin.com/in/bradslavin) ## Take control of your DMARC reports Turn raw XML into actionable dashboards. Start free - no credit card required. [Start Free Trial](https://app.dmarcreport.com/) [Check Your DMARC Record](/tools/dmarc-checker/) ## Related Articles [ Intermediate 4m DKIM Key Rotation Best Practices: Here's What Large Organizations Should Know Apr 8, 2026 ](/blog/dkim-key-rotation-best-practices-for-large-organizations-should-know/)[ Intermediate How to Protect Your Email Server from Cyber Threats May 18, 2026 ](/blog/how-to-protect-your-email-server-from-cyber-threats/)[ Intermediate 3m Secure Your Email Communication By Achieving The Highest Authentication Standards With DKIM Signatures May 10, 2022 ](/blog/secure-your-email-communication-by-achieving-the-highest-authentication-standards-with-dkim-signatures/)[ Intermediate SSL Vs TLS Explained: Key Differences And Why It Matters May 18, 2026 ](/blog/ssl-vs-tls-explained-key-differences-and-why-it-matters/) ```json {"@context":"https://schema.org","@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com","logo":{"@type":"ImageObject","url":"https://dmarcreport.com/images/dmarcreport-logo.png"},"description":"DMARC reporting and email authentication management. 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