DKIM Record Check: What It Reveals And How
To Fix Common Errors


An accurately set up DomainKeys Identified Mail (DKIM) record is crucial for ensuring email authentication, enhancing deliverability, and safeguarding against spoofing threats. Conducting a DKIM record verification allows domain administrators to confirm that their configuration is accurate and operational. However, numerous administrators face perplexing error messages, misconfigurations, or system failures that can negatively impact their email reputation.

This guide provides a comprehensive overview of what a DKIM record verification entails, how to interpret the findings, and offers solutions for common DKIM errors that may compromise your domain's security and operational efficiency. Visit www.duocircle.com. for more details.


What Is a DKIM Record Check and Why Does It Matter?


A DKIM record verification is a systematic evaluation aimed at ensuring that the DNS TXT record for DKIM associated with your domain is accurately published and that your email server is appropriately signing outgoing communications. These assessments validate that:

  • Your public DKIM key is visible in DNS

  • The signature is valid and matches the private key

  • The correct selector is in use

  • Email headers and body content remain intact in transmission

Consistently monitoring DKIM allows for the identification of configuration errors that may lead to email delivery issues or hinder the effective implementation of DMARC policies.



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What a DKIM Record Check Reveals


  • DNS TXT Record Status: A DKIM record verification will assess the presence of a TXT record at the appropriate subdomain, typically formatted as selector._domainkey.domain.com. Should this record be absent, any attempt at DKIM verification will result in an immediate failure.

  • Record Syntax and Key Format: The tool checks if the DKIM record:

    • Uses the correct tags (v=DKIM1, k=rsa, p=public key)

    • Has a properly encoded and complete RSA public key

    • Incorrect formatting leads to a syntax error or rejection by receiving mail servers.

  • Key Length and Security Strength: Contemporary security protocols advocate for the use of 2048-bit keys to ensure optimal security. DKIM record verification tools flag keys that are less than 1024 bits in length as vulnerable, which frequently leads to their rejection by leading service providers such as Gmail and Microsoft.

  • DKIM Selector Validity: The selector is an integral component of the DNS query. Utilizing an incorrect or obsolete selector will result in the inability to locate your DKIM public key. Conducting a thorough DKIM verification can assist in determining whether you are employing the appropriate selector.

  • Signature Verification Result: Certain DKIM validation tools extend their analysis beyond mere DNS records by assessing actual emails to verify the authenticity of the DKIM signature.

    • Is present

    • Matches the headers and body

    • Has passed or failed validation

Common DKIM Errors and How to Fix Them


No DKIM Record Found

  • Cause: The DNS record has not been established or is currently absent.

  • Fix:

Verify that the correct selector is being used.

Check your DNS provider and add the DKIM TXT record at selector._domainkey.yourdomain.com.

Invalid DKIM Record Syntax

  • Cause: Issues related to formatting, including absent semicolons, incorrect spacing, or faulty tag organization.

  • Fix:

Ensure your record follows this format:

ini

v=DKIM1; k=rsa; p=yourpublickey

Avoid line breaks or hidden characters when copying keys into DNS.



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Public Key Too Short

  • Cause: The DKIM key measures just 512 bits in length, rendering it insecure and generally deemed inadequate by many.

  • Fix:

Generate a new key pair with 1024-bit or 2048-bit RSA length.

Update the DNS TXT record with the new public key.

Selector Not Found

  • Cause: The email server you are using is utilizing a selector that lacks a corresponding DNS record.

  • Fix:

Verify the selector name used in your mail system.

Create a matching DNS record under selector._domainkey.yourdomain.com.

Signature Verification Failed

  • Cause: The content of the email that was signed has been altered post-signature, or there is a mismatch between the public and private key pair.

  • Fix:

Verify that no mail relay or filtering system is modifying the email headers or content following the signing process.

Verify that the private key on your mail server corresponds correctly with the public key listed in the DNS records.

Multiple DKIM Records

  • Cause: You have published multiple DKIM records with the same selector.

  • Fix:

Consolidate into a single TXT record for each selector.

Avoid overlapping selectors across different mail services unless coordinated.