B2B email decay report 2026: what changes and when to reverify

People change jobs, domains are replaced, mailboxes are disabled, and receiving infrastructure changes its response. A record can move from valid to invalid, valid to catch-all, or valid to unknown. Unknown can also reflect a temporary inability to obtain a decisive SMTP response rather than a dead mailbox.

A useful decay system stores the prior state, new state, timestamps, verifier, response reason, and intended use. That makes a recheck auditable and prevents repeated calls immediately after a stable result.

ZeroBounce says its 2026 report is based on 11 billion addresses submitted during 2025: more than 2.6 billion invalid, more than 1 billion catch-all, and 62 percent valid. Because customers choose which lists to submit, the dataset can overrepresent old, risky, or uncertain lists.

Use the report as evidence that decay and non-valid states are operationally material. Do not use it to claim that every B2B list loses exactly 23 percent per year or that a specific provider has that error rate.

Verify immediately before the first paid export or campaign. Reverify reused campaign files when the previous result is older than the risk window. Shorten that window for older scraped lists, job-change-heavy roles, catch-all domains, or campaigns where a bounce has high reputational cost.

Cache stable results to avoid unnecessary repeated verification, but define a time-to-live and invalidate the cache when the underlying record, domain, or provider evidence changes.