Why evidence, not just valid / invalid
MailCheck helps outbound systems decide who is safe to contact and how much uncertainty remains before sending. It is a risk and reputation layer — not a sales-conversion or enrichment product.
The problem with one score
A binary "valid / invalid" verdict hides the part that actually protects your sender reputation: how much uncertainty remains. An address can accept SMTP yet be a catch-all sink, a role inbox, or a recipient that rejects your specific mail. Flattening that into "valid" is how false-valid results reach the sender.
What the evidence shows
In a closed-beta validation of 93 real outbound contacts (design partner Nebula, August 2026), only 41 were cleared by both a major verifier and internal policy. The distribution:
| Classification | Contacts |
|---|---|
| HIGH_CONFIDENCE_VALID | 43 |
| ACCEPT_ALL (catch-all) | 26 |
| CONNECTION_FAILED | 17 |
| Unverifiable / temporary | 4 |
| CONFIRMED_INVALID | 2 |
| Unavailable | 1 |
The 26 catch-all and 4 unresolved results are risk classification, not sales objections. MailCheck's job is to surface how much uncertainty remains, not to greenlight conversion.
One episode
A major verifier scored an address valid, 100/100. MailCheck returned CONFIRMED_INVALID (SMTP recipient rejected). The partner's own send history showed a hard bounce. MailCheck preserved the rejected-SMTP evidence the other tool buried.
What MailCheck measures
The beta measures reputation outcomes, not conversions:
- Hard-bounce rate among MailCheck-cleared contacts.
- Hunter-valid contacts blocked by MailCheck that would otherwise have been risky.
- False-valid rate by the legacy verifier.
- False-invalid / unnecessary-block rate by MailCheck.
- Reputation incidents prevented.
- Inbox and sender-health stability.
- Evidence quality when a delivery failure occurs.
Sales, replies, and payments are downstream business outcomes — not MailCheck's job.
Honest scope
This is a design-partner validation across 93 contacts — a signal, not a claim of accuracy superiority. The public beta will measure false-valid rates at cohort scale before any comparative claim is made. MailCheck does not authorize sending; the consumer's release gate decides, keyed on classification.