Every company sending email is playing a game they can't see the rules of. Gmail, Outlook, and Yahoo each run shifting filtering logic, and most teams only notice when it fails: open rates drop, password resets land in spam, a blocklist hit tanks reputation on a shared IP nobody knew about.

We built InboxStack after watching this problem from inside enterprise deliverability, including building KARMA, a dashboard deployed at Epsilon. That taught us monitoring isn't the hard part — every tool can show that something broke. Almost none explain why.

So we built Brain, a causal AI engine trained on a 22-year deliverability knowledge base. It correlates signals across your ESP, DNS authentication (SPF, DKIM, DMARC), Google Postmaster Tools, Microsoft SNDS, and 50+ blocklists to trace the actual root cause — not "placement dropped 12%," but the DKIM misalignment that caused it.

Onboarding starts in minutes: forward your headers for an instant DNS audit, no migration required. Built for agencies