DKIMDiff

DKIMDiff is a web app (with optional CLI agent) that continuously verifies DKIM alignment and signing consistency across your real sending sources—not just what you think is configured. It discovers outbound mail streams by ingesting headers from seed inboxes and/or SMTP relay logs, then compares observed DKIM selectors, domains, canonicalization, and signature validity against your intended policy. When a vendor flips selectors, a subdomain starts signing incorrectly, or a new system sends unsigned mail, DKIMDiff flags it with a clear “what changed, when, and where” diff. It also runs scheduled DNS checks for missing/expired keys, oversized records, and propagation issues, and provides step-by-step remediation guidance per ESP (SendGrid, SES, Mailgun, Postmark, etc.). This is not a magical deliverability fixer; it’s a practical early-warning system that reduces silent breakages that cause sudden inboxing drops.