DKIM Validator

The DKIM Validator performs cryptographic verification of DKIM signatures against the domain's DNS key record. It accepts a domain, selector, DKIM-Signature header value, and the raw email body, then fetches the DNS TXT record for selector._domainkey.domain. The tool canonicalizes the header and body per RFC 6376, computes the body hash, and verifies the RSA signature using the retrieved public key. Results include a pass/fail verdict, key algorithm, and alignment status. The tool is valuable during initial DKIM deployment, post-migration checks, or incident response when signature failures or body hash mismatches occur. It helps security teams ensure consistent authentication behavior and improve deliverability by surfacing actionable misconfigurations. Unique value lies in combining DNS key retrieval, signature verification, and alignment checks into a single diagnostic report, with clear guidance on remediation. Core features include multiple selector support, configurable canonicalization, and exportable results for audits. Common use cases include validating new domains, diagnosing failed deliveries, and verifying that header/body hashes remain intact after mail processing. This tool does not replace mail delivery systems or SPF/DMARC evaluations but complements them by strengthening DKIM-based authentication and aiding root-cause analysis.