See if Linode works for you with $100 in credit

Linode accelerates innovation by making cloud computing simple, accessible, and affordable to all. Founded in 2003, Linode helped pioneer the cloud computing industry and is today the largest independent open cloud provider in the world. Headquartered in Philadelphia's Old City, the company empowers more than a million developers, startups, and businesses across its global network of 11 data centers.

InboxStack is an email deliverability intelligence platform built for teams who need to know why their emails aren't reaching the inbox — not just that they aren't. At its core is Brain, a proprietary causal AI engine trained on a 22-year deliverability knowledge base, which correlates signals across your ESP, DNS authentication records (SPF, DKIM, DMARC), Google Postmaster Tools, Microsoft SNDS, and 50+ blocklists to pinpoint root causes instead of surfacing raw metrics.

Most deliverability tools stop at monitoring: they show you a drop in inbox placement or a blocklist hit and leave you to investigate. InboxStack goes further, tracing the actual causal chain — a DKIM misalignment, a reputation dip on a specific sending IP, a content trigger — so you can fix the real problem instead of guessing.

Setup takes minutes with no migration required: forward your email headers for an instant DNS/authentication audit, or connect your existing ESP and Postmaster accounts for ongoing monitoring. Optional seed testing gives you real inbox-vs-spam placement data across major providers.

Built for agencies managing multiple client domains and growing companies who've outgrown basic authentication checkers, InboxStack turns deliverability from a black box into a diagnosable, fixable system.