What causes invalid RSA public key errors in DKIM records and how can I fix it?
Summary
What email marketers say10Marketer opinions
Email marketer from Reddit recommends careful copy/pasting of the DKIM record into DNS, because extra spaces, line breaks, or incorrect characters can easily be introduced. They advise using a text editor to clean up the key before pasting it into DNS.
Email marketer from Stack Overflow suggests an invalid RSA public key can arise during the key generation process itself if the parameters are incorrect or if the software used for generation has bugs. They advise trying a different key generation tool or verifying the parameters used.
Email marketer from Server Fault explains key mismatches are where the public key in the DNS record doesn't match the private key used to sign emails. They suggest verifying you're using the correct key pair and that no modifications have occurred during key transfer.
Email marketer from MXToolbox recommends using online DKIM checkers to diagnose issues. These tools can identify syntax errors, key mismatches, and other common problems.
Email marketer from Mailhardener advises DNS propagation delays can cause temporary errors. They say waiting 24-48 hours after adding/modifying the DKIM record before troubleshooting can resolve the issue.
Email marketer from Email Geeks shares experiences of DKIM cut/paste errors introducing line breaks or extra spaces from text editors or DNS providers, which can break the key.
Email marketer from Super User suggests some DNS providers have character limits for TXT records. If the DKIM key exceeds this limit, it can be truncated, leading to errors. Solutions include splitting the key into multiple TXT records (if supported) or using a provider with higher limits.
Email marketer from Reddit shares that base64 encoding issues can result in invalid RSA keys. They advise checking the encoding process, ensuring no characters are corrupted during encoding/decoding and using a reliable base64 encoder.
Email marketer from Email on Acid explains that regular testing is important to identify DKIM issues early. They recommend sending test emails to various email providers and checking the headers to confirm DKIM signing is working correctly.
Email marketer from dmarcian says a revoked or expired DKIM key will cause validation failures. They suggests ensuring the key is active and hasn't been intentionally revoked.
What the experts say3Expert opinions
Expert from Word to the Wise explains that an incorrect key length can be an issue for DKIM. Standard key sizes are 1024 bits or 2048 bits; anything shorter is typically rejected. They suggests checking if the key was generated with the correct length.
Expert from Email Geeks suggests a bad base64 decode indicates the DKIM key is malformed, possibly truncated or corrupted during DNS management insertion, noting the key in DNS is an odd number of characters long.
Expert from Word to the Wise highlights that using an incorrect selector can cause validation failures. They advise double-checking that the selector used in your email headers matches the selector in your DNS record.
What the documentation says5Technical articles
Documentation from Google explains that strict adherence to DNS syntax rules is essential. For Google Workspace, they provide specific examples and guidelines for DKIM record formatting, which should be followed precisely.
Documentation from OpenSSL explains that if the version of OpenSSL used to generate the key is incompatible with the software validating it, errors can occur. Upgrading OpenSSL or regenerating the key with a compatible version is suggested.
Documentation from DKIM.org shares that canonicalisation issues between the signing and verification processes can trigger false negatives. Ensuring consistent canonicalisation algorithms are used is critical.
Documentation from ietf.org explains that the DKIM standard (RFC 6376) requires specific syntax for the public key record. Incorrect formatting, such as missing semicolons or incorrect tag-value pairs, will cause parsing errors. Strict adherence to the RFC is necessary.
Documentation from Cloudflare explains that incorrect DNS record syntax, including extra spaces or incorrect characters, can lead to errors. They suggest carefully reviewing the record for typos and ensuring it matches the provider's requirements.