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DKIM Canonicalization Best Practices (relaxed vs simple)
Choose the right DKIM canonicalization mode to balance robustness and strictness.
1 min read
Updated 2025-10-23
Tutorials
dkimcanonicalizationrelaxedsimple
Overview: Understand relaxed vs simple canonicalization to avoid false negatives and preserve integrity.
Prerequisites: Access to DKIM signer configuration.
Steps
- Prefer
relaxed/relaxedin most cases to handle benign whitespace changes. - Use
simpleonly when you control all transformations end-to-end. - Test across MTAs and gateways that may rewrap headers.
Verification
- Signature validation: DKIM Checker
- Header diffs: Header Analyzer
Troubleshooting
- Failing signatures: switch body canonicalization to relaxed.
- MIME changes: ensure signer normalizes content consistently.
FAQ
Q: Does canonicalization affect DMARC? A: Indirectly; DKIM success is part of DMARC alignment.