Most tools measure the easy case.
A simple mailbox check already gets that right. It goes to zero on the hard case — the one that decides whether verification was worth paying for at all.
That’s the number below, and it’s the one every incumbent’s marketing page skips.
share of B2B addresses on catch-all domains
— MailerCheck’s own 33,000-list study
Live accuracy data.
Pulling the latest bounce-outcome data…
How calibration works.
{"tested": "controlled domain we own, known real + fake mailboxes","found": "every real mailbox resolved; every fake one held at low confidence, never confirmed","pass_rate_strict": 0.52,"false_confirm_rate": 0.0,// a stronger signal exists here but is rate-limited upstream"ceiling_reason": "reserved for a rarer, higher-severity failure mode — a tradeoff, not a bug"}
A documented gap you can verify beats an inflated number you can’t.
One narrow, controlled test case — doesn’t cover general SMTP, non-catch-all domains, or other providers; those are measured separately above.
Vendor-reported benchmarks.
Vendor-published, not independent audits.
{
"competitor": "Hunter",
"metric": "top_accuracy_score",
"value": 0.70
}/* Source: Hunter's own 3,000-email test of 15 verifiers, itself included */
{
"competitor": "ZeroBounce",
"metric": "catchall_false_positive_rate",
"value": 0.081
}/* Source: Allegrow's own 1,222-email test — missed 30% of real contacts */
Accuracy targets by segment.
| Segment | Target accuracy |
|---|---|
| Non-catch-all (standard SMTP) | ≥ 99% |
| Enterprise tenant catch-all | ≥ 95% |
| Google Workspace catch-all | 75–85% |
| Generic SMTP catch-all | 65–80% |
| SEG-fronted (Proofpoint/Mimecast) | 60–75% |
Feature comparison.
Checked against public vendor docs, July 2026 — not an independent audit.
| Feature | skink | ZeroBounce | NeverBounce | Kickbox | BriteVerify |
|---|---|---|---|---|---|
| Catch-all resolution* | resolved if confident | paid add-on | accept-all | risky | accept-all |
| Microsoft 365 check | resolved | not supported | not supported | not supported | not supported |
| Google Workspace catch-all | probabilistic | not supported | not supported | not supported | not supported |
| SEG handling | resolved | Silent unknown | Silent unknown | Silent unknown | Silent unknown |
| Greylisting† | auto-retry | not supported | some | supported | partial |
| Confidence score | confidence score | paid add-on | binary | Sendex score | binary |
| Exposed reasoning | reasons[] + signals | not supported | not supported | not supported | not supported |
| Credits never expire‡ | forever | 2yr (new) | 12mo | 12mo | 12mo |
Hover any icon for detail.
* Catch-all resolution: Provider-specific out-of-band checks return a real verdict when the signal is strong; ambiguous cases still return risky.
† Greylisting: Detected automatically — set allow_async_followup to retry in the background once the greylist window passes.
‡ Credits never expire: ZeroBounce: 2-year expiry for new signups; pre-June-2026 customers keep no-expiry.
See it on your own list before you spend anything.
Start free — 100 credits