Overview
DKIM adds a cryptographic signature to your emails so receivers can confirm they were not altered in transit. A "body hash did not verify" error means the message body changed after signing, causing authentication to fail. This guide explains the causes and fixes.
Key Takeaways
- DKIM signs the message so tampering can be detected.
- A body-hash failure means the body changed after signing.
- Mailing lists, forwarders, and footers commonly alter the body.
- Correct DKIM configuration and consistent content resolve it.
Common Causes and Fixes
1. Check whether a mailing list or forwarder is modifying the message; these often break DKIM.
2. Ensure only one system signs the message, and it signs the final content.
3. Avoid post-signing changes such as appended footers or link rewriting.
4. Verify your DKIM key and selector in DNS match the signing configuration.
Verify Your Setup
1. Send a test message to a DKIM-checking service or your own account.
2. Inspect the authentication results header for the DKIM outcome.
3. Confirm the body hash passes after your changes.
4. Align DKIM with SPF and DMARC for the best deliverability.
Note: Forwarding through mailing lists that add footers is a frequent, expected cause; DMARC alignment with SPF can still let such mail pass.
Troubleshooting
Problem: DKIM fails only for forwarded mail.
Solution: Forwarders that modify the body break the hash; rely on SPF alignment or ARC where supported.
Problem: All your mail fails DKIM.
Solution: Check that the published DKIM public key and selector in DNS match your signing keys.
Problem: A footer or disclaimer breaks signing.
Solution: Apply footers before signing, or sign the final message so the body is not changed afterward.
Problem: Two systems both sign the message.
Solution: Ensure only the final sending system applies the DKIM signature.
Conclusion
The DKIM body-hash error means the message changed after it was signed. Sign the final content, avoid post-signing edits, and confirm your DNS keys match to pass verification.
About TechHub
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