BounceZero Research - Recurring Index

The BounceZero Deliverability Barometer

A quarterly, composition-controlled read on the state of B2B email, computed from the BounceZero verification network. Each quarter is frozen and versioned, so a figure you cite today stays reproducible for years. This is the running index behind our deliverability research.

What each reading means

• Ambient invalid rate - the share of addresses across the corpus that are already dead. The baseline bounce risk of an unverified B2B list.
• True catch-all - accept-all configuration on verifiable business mail (Microsoft 365 + Google Workspace), stripped of the consumer-provider noise that inflates naive catch-all figures. See the catch-all study.
• 90-day survival - of addresses verified valid, the share still valid when re-checked more than 90 days later. The lower it is, the faster clean lists rot. See the decay study.
• Role-based bounce rate - how often role-based addresses (info@, contact@) come back invalid; on cold data this is a proxy for how much of the market is list-guessing. See the role-based study.

Why quarterly, and not monthly

We publish this on a quarterly cadence deliberately, and it is worth being candid about why. A verification network's month-to-month numbers are dominated by composition - which lists happened to run that month - not by real shifts in email health. A naive monthly index computed on our corpus swings from the 30s to the 80s and back, which would be worse than useless: it would look precise while measuring noise. A quarter aggregates enough breadth, with the same composition controls we use across our studies, to move for real reasons. When our customer-traffic volume is large enough to isolate on its own, we will revisit a monthly cadence; until then, a quarter is the shortest honest window.

Methodology & limitations

Each component is computed with the composition control appropriate to it - true catch-all on verifiable business providers, decay on re-verified addresses, and so on - over domain-day aggregates, with no individual addresses involved and a k-anonymity floor of 50 distinct domains on any published cell. Every quarter is frozen in a versioned snapshot and remains reproducible against it. The standing caveat from all our research applies: the corpus over-weights outbound prospecting traffic, so these are readings on the world our network sees, not a census of all email.

Cite a reading as: "BounceZero Deliverability Barometer, [quarter] (bouncezero.io/email-deliverability-index)." Want your own list scored against the current barometer? Verify a list free.