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
Calibration evidence.
Owned-domain checks help test behavior. They do not establish production accuracy across providers or prove final delivery.
A narrow owned-domain sample. Some mailbox labels remain unverified.
SMTP responses describe what the server reported at probe time. Delivery outcomes require separate evidence.
A representative, independently labeled evaluation is required.
No general false-confirm rate is claimed from this sample.
Confidence scores are estimates, not delivery guarantees. Catch-all and policy-blocked servers can remain unresolved even when their mail infrastructure is healthy.
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 | Difficulty |
|---|---|---|
| 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 resolution1 | 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 |
| Greylisting2 | 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 expire3 | forever | 2yr (new) | 12mo | 12mo | 12mo |
Hover any icon for detail.
1 Catch-all resolution: Provider-specific out-of-band checks return a real verdict when the signal is strong; ambiguous cases still return risky.
2 Greylisting: Detected automatically — set allow_async_followup to retry in the background once the greylist window passes.
3 Credits never expire: ZeroBounce applies a 2-year expiry to new signups; pre-June-2026 customers keep no-expiry terms.
See it on your own list before you spend anything.
Start free — 100 credits