How does a missing DKIM DNS TXT record affect email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 9 Aug 2025
Updated 19 Aug 2025
8 min read
When you send an email, you expect it to land in the recipient's inbox. However, the journey from sender to recipient is complex, involving numerous checks and validations. One of the most crucial elements in this process is DomainKeys Identified Mail (DKIM). DKIM signature helps mailbox providers verify that an email was indeed sent by an authorized server and that its content hasn't been tampered with during transit.
A core part of DKIM relies on a public key published in your domain's DNS as a TXT record. So, what happens if you have DKIM signing enabled on your email server, but that essential public key is nowhere to be found in your DNS? This common oversight can significantly impact your email deliverability, potentially leading to messages being flagged as spam, deferred, or even outright rejected by receiving mail servers. The absence of this key means the signature cannot be validated, essentially rendering DKIM authentication useless.
DKIM works by using a cryptographic pair of keys: a private key and a public key. Your sending mail server uses the private key to generate a unique digital signature for each outgoing email. This signature is then embedded in the email's header. The corresponding public key is published as a TXT record in your domain's DNS, typically under a specific DKIM selector.
When a recipient's mail server receives an email, it looks for the DKIM signature in the header. It then queries the sender's DNS for the public key associated with the DKIM selector specified in the signature. If the public key is found, the receiving server uses it to decrypt the signature and verify that the email (including its headers and body) has not been altered since it was signed and that it genuinely originated from the claimed domain.
A missing DKIM DNS TXT record means that when the receiving server attempts to retrieve the public key, the DNS lookup will fail. Without the public key, the receiving server cannot verify the digital signature on your email. This failure to authenticate can severely damage your email's trustworthiness, despite your server attempting to sign the emails.
Immediate impacts on deliverability
The immediate consequence of a missing DKIM DNS TXT record is a failed DKIM authentication. When DKIM fails, it sends a strong negative signal to the recipient's mail server. Many email service providers (ESPs) and mailbox providers, including major ones like Google and Yahoo, rely heavily on email authentication protocols such as DKIM to combat spam and phishing.
Emails that fail DKIM authentication are often treated with suspicion. They might be routed directly to the spam or junk folder, quarantined, or even rejected entirely. This can lead to a significant drop in your inbox placement rates. It's crucial for your emails to pass authentication checks to ensure they reach their intended recipients, as incorrectly configured DKIM records can cause legitimate emails to be marked as spam or blocked.
Moreover, a consistent pattern of DKIM authentication failures can negatively affect your domain's sender reputation. Over time, if your emails repeatedly fail DKIM checks due to a missing DNS record, your domain may be added to internal blocklists (or blacklists) maintained by ISPs, making it even harder for your emails to reach the inbox in the future. To understand more about how these lists work, you can check our guide on what happens when your domain is on an email blacklist.
Is a missing record worse than no DKIM at all?
This is a nuanced point. Technically, a missing DKIM DNS TXT record results in a DKIM validation failure, which essentially means the email is treated as if it were unsigned. From a pure authentication protocol standpoint, the outcome might seem similar: the email lacks a valid DKIM authentication pass. However, some argue that attempting to sign an email and then failing to provide the public key for verification might be perceived worse by some receiving systems or their machine learning filters.
Why might this be the case? When an email arrives with a DKIM signature in its header but the public key isn't found, it indicates a misconfiguration rather than a complete absence of the authentication attempt. While some recipient servers might treat a failed DKIM authentication the same as no DKIM at all, others might interpret the misconfiguration as a potential red flag, suggesting negligence or even a spoofing attempt if the signature itself appears malformed or invalid without a corresponding public key. As one perspective notes, emails you sign without having actual domain with keys will end up to junk eventually.
However, others argue that there's no difference between a mail with no DKIM header and one with a signature that doesn’t validate. They are both unsigned mail from DKIM's perspective. The public emphasis on authentication by major providers suggests that any authentication failure can be detrimental, regardless of the cause. You can read more about how turning on DKIM impacts deliverability in our dedicated article.
The current landscape of email security, especially with new sender requirements from Google and Yahoo, places a high emphasis on strong authentication. A valid DKIM record is now practically a baseline expectation for good deliverability. Therefore, a missing record can have a more pronounced negative impact, as it signals a breakdown in a security measure that recipients' servers expect to be correctly implemented.
Rectifying and preventing missing DKIM records
The solution to a missing DKIM DNS TXT record is straightforward: publish the correct public key as a TXT record in your domain's DNS. Your email service provider or mail server documentation should provide the exact DKIM record (including the selector name and the public key value) that needs to be added. This record typically looks something like selector1._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIGfMA0GSIb3DQEBAQUAA4GNADCBiQKBgQDy8Wz9X1M6h1J2B4Z7F7Q3K2N4L5P6R7S8T9U0V1W2X3Y4Z5A6B7C8D9E0F1G2H3I4J5K6L7M8N9O0P1Q2R3S4T5U6V7W8X9Y0Z1A2B3C4D5E6F7G8H9I0J1K2L3M4N5O6P7Q8R9S0T1U2V3W4X5Y6Z7A8B9C0D1E2F3G4IJKLMNOPQRSTUVWXYZabcdefghijklmnoqrstuvwxyz+/=ExampleKey".
Example DKIM DNS TXT recordDNS
selector1._domainkey.yourdomain.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDy8Wz9X1M6h1J2B4Z7F7Q3K2N4L5P6R7S8T9U0V1W2X3Y4Z5A6B7C8D9E0F1G2H3I4J5K6L7M8N9O0P1Q2R3S4T5U6V7W8X9Y0Z1A2B3C4D5E6F7G8H9I0J1K2L3M4N5O6P7Q8R9S0T1U2V3W4X5Y6Z7A8B9C0D1E2F3G4IJKLMNOPQRSTUVWXYZabcdefghijklmnoqrstuvwxyz+/=ExampleKey"
After adding the record, DNS propagation can take some time (from minutes to several hours), so it's essential to monitor your email deliverability and DMARC reports to confirm that DKIM is now passing successfully. Regularly checking your DNS records for all your sending domains is a crucial best practice to prevent such issues from arising. This proactive approach ensures your email authentication remains robust and your sender reputation stays intact. You can find more information about DKIM selector name examples in our guides.
Tools are available that can help you verify your DKIM records and ensure they are correctly published. These tools perform a lookup of your DKIM TXT record and confirm its validity, providing peace of mind and helping to troubleshoot any potential issues before they impact your email campaigns. For broader insights into how different authentication methods work together, explore our simple guide to DMARC, SPF, and DKIM.
Views from the trenches
Critical impact of missing DKIM
Reduced inbox placement: Emails are more likely to land in spam folders or be rejected.
Damaged sender reputation: Repeated failures can lead to your domain being blocklisted (or blacklisted).
DMARC failure: If DKIM is your only passing authentication method, DMARC will fail.
With a valid DKIM record
Email is cryptographically signed and verifiable.
Receiving servers can confirm sender authenticity and message integrity.
Higher likelihood of reaching the inbox and building a strong sender reputation.
With a missing DKIM record
Email is signed, but the signature cannot be verified due to missing public key.
Receiving servers treat the email as unauthenticated or misconfigured.
Increased risk of emails being marked as spam or rejected, damaging reputation.
Fails DKIM alignment, potentially DMARC depending on policy and SPF status
Incorrect public key in DNS
Signature verification fails; similar to missing record
Fails DKIM alignment
DKIM not enabled on sending server
No DKIM signature present; relies solely on SPF and DMARC policy
No DKIM result (neutral)
DKIM body hash mismatch
Indicates content modification; leads to authentication failure
Fails DKIM alignment
Views from the trenches
Best practices
Always publish your DKIM DNS TXT records correctly to ensure successful email authentication.
Regularly monitor your DMARC reports to identify any DKIM failures and address them promptly.
Ensure consistency between your sending server's DKIM signing and your published DNS records.
Common pitfalls
Forgetting to publish the DKIM public key after enabling signing on your email server.
Incorrectly formatting the DKIM DNS TXT record, leading to validation errors.
Assuming that DKIM failures are less impactful than not having DKIM at all.
Expert tips
Use automated tools to check your DKIM records periodically and ensure they remain valid.
Understand that even subtle misconfigurations can lead to deliverability issues and reputation damage.
Keep up-to-date with changes in sender requirements from major mailbox providers.
Expert view
Expert from Email Geeks says a DKIM failure is generally treated similarly to no DKIM signature at all, as the main point is whether the signature validates or not.
2024-04-12 - Email Geeks
Expert view
Expert from Email Geeks says they were previously informed by Yahoo that DKIM failures weren't penalized, but recent emphasis on authentication suggests this stance has likely changed.
2024-04-12 - Email Geeks
Summary of impact
A missing DKIM DNS TXT record is a critical issue that can severely hamper your email deliverability. While some might consider it on par with not using DKIM at all, the act of attempting to sign an email without providing the necessary public key for verification can, in some cases, even be perceived as a more concerning misstep by advanced spam filters. Proper DKIM setup is a non-negotiable aspect of modern email deliverability, especially with updated sender requirements from major ISPs.
Ensuring your DKIM records are correctly published and consistently maintained is vital for establishing trust with mailbox providers and ensuring your legitimate emails reach the inbox. Regularly audit your DNS records and monitor your email authentication reports to catch and rectify any discrepancies promptly. Proactive management of your DKIM records is key to maintaining a healthy sender reputation and achieving optimal email deliverability with Suped.
Suped.
