Email deliverability is the share of email you send that reaches the recipient's inbox, as opposed to being rejected, bounced, or filed as spam. It depends on authentication (SPF, DKIM, DMARC), sender reputation per domain and IP, list quality, sending patterns and content. The two numbers mailbox providers enforce are a bounce rate under 2% and a spam complaint rate under 0.3%; a list with 14.5% invalid addresses fails the first on its first send.
Deliverability is measured by inbox placement tests (seed lists across providers), by Google Postmaster and Microsoft SNDS reputation dashboards, and by the bounce and complaint rates on each campaign. Delivery rate, the share accepted by the server, is not inbox placement; mail can be accepted and filed as spam.
List quality is the factor a sender controls fastest. Authentication takes an afternoon, reputation takes weeks of warm-up, but a verified list takes minutes and removes the hard bounces that damage reputation. The deliverability checklist covers all four factors.
A new domain is authenticated and warmed for three weeks. The first campaign of 5,000 goes to an unverified list and bounces at 11%. Reputation drops and the next three campaigns land in spam. The same domain, same copy, verified list: 0.5% bounce, inbox placement holds above 90% through the quarter.
Verify a list or a single address. 100 free checks a month, unknowns refunded.
Verify Leads - FreeAyoub built BounceZero's 5-stage validation pipeline, its dedicated BGP-announced IP infrastructure, and the Patroni HA PostgreSQL cluster behind every verification. Previously built high-volume email delivery infrastructure. Trained at 1337 Benguerir (École 42 network, 2019). Open-source: bgp_analyzer.