DKIM Validator

Purpose-built DKIM validation tool for email security teams and system administrators. It verifies whether a DKIM-Signature can be cryptographically validated using the domain's published public key. By isolating the cryptographic step from mailbox testing, it enables precise root-cause analysis of signature failures. The tool accepts a domain, a selector, and the raw DKIM-Signature header (with optional signed headers and body sample) and retrieves the corresponding DNS TXT record at selector._domainkey.domain. It then parses the signature, canonicalizes headers and body per the chosen rules, constructs the data that was signed, and uses the public key to verify the signature with the specified algorithm. This yields a deterministic pass/fail verdict along with diagnostic details. Engineers benefit from clear failure reasons (e.g., missing DNS record, mismatched body hash, or unsupported algorithm) and a repeatable verification workflow. The unique value lies in its transparent DNS lookup + RFC-compliant cryptographic checks, presented in a structured, machine-friendly format for automated workflows and audit trails. Typical use cases include validating deployments after DNS changes, debugging observed signature failures in mail logs, and confirming third-party senders’ DKIM integrity. Outputs include the verification status, signer domain, selector, algorithm, body hash, the retrieved DNS key, and a concise explanation, enabling rapid remediation and higher deliverability.