--- title: "7 reasons why DKIM fails and how to fix it | DuoCircle" description: "DKIM fails for 7 common reasons: wrong selector, missing TXT, body modification, forwarders, key rotation, DNS lag, and signature mismatch. Fixes inside." image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/blog/email-security/7-reasons-why-dkim-fails-and-how-to-fix-it/" --- Quick Answer DKIM fails when the receiving server cannot match the signature to your published public key. Common causes: DKIM was never set up, the DNS record has formatting errors, signed headers (From, Subject, Date, Message-ID) were altered in transit, the public key is missing from DNS, the message was modified by a forwarder or list, or the keys expired without rotation. 7 reasons why DKIM fails and how to fix it Your browser does not support the audio element. [ Download episode](https://media.mailhop.org/duocircle/images/2025/08/7-reasons-why-DKIM-fails-and-how-to-fix-it.mp3) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Femail-security%2F7-reasons-why-dkim-fails-and-how-to-fix-it%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=7%20reasons%20why%20DKIM%20fails%20and%20how%20to%20fix%20it&url=undefined%2Fblog%2Femail-security%2F7-reasons-why-dkim-fails-and-how-to-fix-it%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Femail-security%2F7-reasons-why-dkim-fails-and-how-to-fix-it%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Femail-security%2F7-reasons-why-dkim-fails-and-how-to-fix-it%2F&title=7%20reasons%20why%20DKIM%20fails%20and%20how%20to%20fix%20it "Share on Reddit") [ ](mailto:?subject=7%20reasons%20why%20DKIM%20fails%20and%20how%20to%20fix%20it&body=Check out this article: undefined%2Fblog%2Femail-security%2F7-reasons-why-dkim-fails-and-how-to-fix-it%2F "Share via Email") ![DKIM fails](https://media.mailhop.org/duocircle/images/2025/08/spf-validator-3115.jpg) Sometimes your email just doesn’t reach its recipient. You’ve done everything right, crafted the perfect message, sent it to the correct address, and even authenticated your domain with [email authentication](/resources/email-authentication) protocols. Yet, it gets flagged or doesn’t even land in the receiver’s mailbox. There could be many reasons that this happens, but one of the most **common and overlooked ones** is a failed [DKIM](/resources/what-is-dkim) (DomainKeys Identified Mail) check. DKIM is one of the three major email authentication protocols (along with SPF and DMARC), which help verify the **integrity and authenticity** of your email. Speaking of DKIM, it ensures that your emails haven’t been altered in transit and that they truly come from the domain they claim to. When DKIM fails, it tells the receiving servers that something might be wrong with the incoming message, so it’s best to withhold the message or mark it as suspicious. Although it is a behind-the-scenes step, it directly affects your deliverability, especially if you’re sending the emails to a large audience. In this article, we will look at the seven most common reasons why DKIM fails, and **how to fix them** so your emails can land exactly where they’re supposed to: the inbox. [![inbox](https://media.mailhop.org/duocircle/images/2025/08/spf-record-3115.jpg)](https://media.mailhop.org/duocircle/images/2025/08/spf-record-3115.jpg) ## What happens when DKIM fails? DKIM essentially vouches for your outgoing emails to the receiving server by attaching a **cryptographic signature** that proves your domain authorized the message and hasn’t been tampered with in transit. If the receiving server doesn’t get this assurance because the signature is missing, broken, or can’t be verified, it thinks the message might be fake or changed. As a result, the server may mark the email as suspicious, send it to the [spam folder](https://cybernews.com/news/microsofts-breach-notification-emails-end-up-in-spam-folder/), or even reject it outright, especially if your domain has a strict [DMARC policy](/dmarc/using-the-right-dmarc-policy-in-2025-a-guide/) in place. ## Why does this happen? If an email fails DKIM, it means the public and [private keys](https://www.techtarget.com/searchsecurity/definition/private-key) didn’t match, and the receiving server couldn’t **verify that the message** really came from your domain or that it wasn’t changed along the way. This mismatch can happen because of various reasons; here are some of them: [![public and private keys ](https://media.mailhop.org/duocircle/images/2025/08/spf-record-check-3115.jpg)](https://media.mailhop.org/duocircle/images/2025/08/spf-record-check-3115.jpg) ### You haven’t configured DKIM at all If you haven’t set up DKIM at all, haven’t added the **required keys or the protocol** is disabled for your email service provider, your emails won’t have a [DKIM signature](https://docs.mapp.com/docs/dkim-signature). _So when the receiving server tries to verify your email, it won’t find anything to check, and the email will likely fail DKIM authentication_. ### There are problems with the setup Another reason your email might fail DKIM is incorrect setup. Chances are, you might have **configured DKIM manually**, without using a proper DKIM record generator, which can lead to errors in the [public key](https://www.investopedia.com/terms/p/public-key.asp) format, selector name, or DNS entry. _Even the slightest mistake, like missing characters or poor formatting, can break the record and make the signature unverifiable by the receiving server_. ### The headers are missing When you implement DKIM, it doesn’t sign just the body of your email to verify the integrity of its contents; it also signs specific [email headers](https://proton.me/blog/what-are-email-headers). These are **listed under the h= tag** in the DKIM signature. For instance: [![ email to verify](https://media.mailhop.org/duocircle/images/2025/08/sender-policy-framework-3115.jpg)](https://media.mailhop.org/duocircle/images/2025/08/sender-policy-framework-3115.jpg) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yourdomain.com; s=myselector; h=from:to:subject:date:message-id; bh=base64\_body\_hash; b=base64\_signature; Here, even if one of these headers, like “From,” “To,” “Subject,” “Date”, or “Message-ID,” is missing or altered by the **time the email arrives**, the server won’t be able to match the signature with the expected hash. This causes the DKIM check to fail. ### There is no public key If you have configured DKIM but haven’t added the public key to your DNS, the receiving server won’t be able to verify your email’s signature. For DKIM to do its job, you need both keys, a private key (used to sign the email) and a public key (stored in **DNS for verification**). And often, most teams simply forget to publish the public key or assume the [email service provider](https://www.activecampaign.com/glossary/email-service-provider) has done it for them, which causes DKIM to fail. [![verify your email’s signature](https://media.mailhop.org/duocircle/images/2025/08/spf-record-6770.jpg)](https://media.mailhop.org/duocircle/images/2025/08/spf-record-6770.jpg) ### Issues in server communication Sometimes, the problem might not be at your end, but at the server’s end. Even if your **DKIM setup is correct**, temporary [DNS lookup](https://www.digicert.com/faq/dns/how-does-dns-lookup-work) failures, timeouts, or network issues on the receiving server’s end can prevent the server from retrieving your public key or verifying your DKIM signature, ultimately causing DKIM to fail. ### The message was modified _If your outgoing message was altered in transit to the recipient, the DKIM signature can break_. If even a single character changed along the way, the receiving server won’t be able to match the hash with the original signature, and the DKIM check will fail. This usually happens when emails pass through forwarding services, mailing lists, [spam filters](https://www.fortinet.com/resources/cyberglossary/spam-filters), or antivirus tools, which might add footers, change headers, or reformat content without you knowing. ### The DKIM keys expired For DKIM to work properly, it is important that you rotate the keys regularly and keep both the private key (used to sign your emails) and the public key (published in your DNS) in sync. If the keys are outdated, expired, or no longer match, the receiving server won’t be able to **verify your email’s signature**, and the DKIM check will fail. [![spam filters ](https://media.mailhop.org/duocircle/images/2025/08/spf-record-tester-3115.jpg)](https://media.mailhop.org/duocircle/images/2025/08/spf-record-tester-3115.jpg) ## How to fix DKIM failure? Here’s how you can fix the DKIM failure issue: - Enable DKIM in your email provider settings - Add the public key to your DNS under the correct selector - Instead of typing everything manually, use a DKIM record generator to avoid formatting mistakes - Sign all required headers and use relaxed/relaxed canonicalization - Rotate your **keys regularly and update** the new ones on the DNS - Avoid services that modify emails after sending - Test your DKIM setup Do you need help **implementing DKIM**? It’s best if you don’t try to do it manually. [Reach out](/contact) to [DuoCircle](/) to get started with error-free DKIM setup. ## Topics DKIMDMARCemail header ![Brad Slavin](https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg) Brad Slavin General Manager General Manager at DuoCircle. Product strategy and commercial lead across the email security portfolio. ## Secure your email infrastructure Protect, authenticate, and deliver. Contact our team to find the right solution. [Contact Sales](/contact/) [Explore Products](/products/) ## Related Articles [ Email Security 3m What are the best practices to follow for managing DKIM keys? Oct 25, 2024 ](/blog/email-security/best-practices-to-follow-for-managing-dkim-keys/)[ Email Security 11m Email Security Risks in Affiliate Marketing Campaigns Jun 13, 2025 ](/blog/email-security/email-security-risks-in-affiliate-marketing-campaigns/)[ Email Security 5m The key differences between Sender Policy Framework and Sender ID Feb 11, 2025 ](/blog/email-security/the-key-differences-between-sender-policy-framework-and-sender-id/)[ Email Security 8m Designing A Custom Dkim Architecture For High-Volume Email Senders Apr 28, 2026 ](/blog/designing-custom-dkim-architecture-for-high-volume-email-senders/) ```json {"@context":"https://schema.org","@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com","logo":{"@type":"ImageObject","url":"https://www.duocircle.com/images/duocircle-logo.png"},"description":"DuoCircle is a portfolio of specialized email products covering protection, authentication, delivery, and routing. 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