ZeroBounce led the field at 98.0% accuracy.
The nearest competitor, BounceBan, scored 86.1% - a gap of nearly 12 percentage points on identical data.
JULY 2026 BENCHMARK•9 TOOLS TESTEDLast updated: September 7, 2026
ZeroBounce scored 98.0% accuracy against 9 email verification tools
On the addresses that break every other tool.
Tested on the same 9,901 addresses drawn from the hardest domain pools to validate. Just 0.6% came back catch-all, 0% unknown. Every disputed result was manually verified by deliverability engineers to establish ground truth.
Self-conducted by ZeroBounce, July 2026. Methodology and aggregated category data published in full.
Full methodology and breakdowns below.
SECTION 01
Overall results
Every tool's full verdict breakdown on the same 9,901-address benchmark list, sorted by accuracy.
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce™ | 98.02% | 1.38% | 0.60% | 0% |
| BounceBan™ | 86.06% | 13.57% | 0.20% | 0.14% |
| Bouncer™ | 84.41% | 2.00% | 8.49% | 5.10% |
| Allegrow™ | 82.05% | 6.34% | 11.61% | 0% |
| Email Oversight™ | 68.77% | 3.33% | 12.28% | 15.17% |
| AtData™ | 68.38% | 5.41% | 23.47% | 2.74% |
| KickBox™ | 64.71% | 2.85% | 18.04% | 14.40% |
| Emailable™ | 61.79% | 0.79% | 34.18% | 3.15% |
| NeverBounce™ | 34.08% | 3.83% | 11.91% | 50.19% |
SECTION 02
Key Findings
The patterns that matter most from this benchmark: where tools pulled apart on accuracy, unknowns, catch-alls, and mailbox providers — and what that means for the results you can actually use.
Unknown rates are where tools diverge most.
ZeroBounce returned 0% unknowns; NeverBounce returned 50.2%. An unknown is an unusable result - the address still has to be verified somewhere else.
Failed-to-validate rates separate the field.
Emailable returned a catch-all verdict on 34.2% of addresses, AtData on 23.5%, and KickBox on 18.0% - resolvable addresses left without an answer. ZeroBounce failed to validate just 0.6%.
Accuracy varies dramatically by mailbox provider.
NeverBounce scored 98.9% on Gmail but 1.4% on Mimecast. A tool's headline accuracy means little if your list skews toward providers it can't handle.
Accuracy and unknown rate together determine what you actually pay per usable answer.
See "The real cost of an unknown" below.
SECTION 03
The real cost of an unknown
A check that returns "unknown" isn't an answer - it's an address you still have to verify somewhere else. The real price of a tool is what you pay per usable result. ZeroBounce returned 0% unknowns in this benchmark; NeverBounce returned 50.2% and charges a credit for every check regardless of outcome1, roughly doubling its effective cost per usable answer.
| Tool | Unknown rate | Usable results per 10,000 checked |
|---|---|---|
| ZeroBounce | 0% | 10,000 |
| Allegrow | 0% | 10,000 |
| BounceBan | 0.14% | 9,986 |
| AtData | 2.74% | 9,726 |
| Emailable | 3.15% | 9,685 |
| Bouncer | 5.10% | 9,490 |
| KickBox | 14.40% | 8,560 |
| Email Oversight | 15.17% | 8,483 |
| NeverBounce | 50.19% | 4,981 |
1 NeverBounce billing documentation: "1 credit = 1 email verification," with no published exemption for unknown results; credits expire 365 days after purchase. ZeroBounce credits never expire with an active ZeroBounce ONE subscription. Verified 5 August 2026.
SECTION 04
Results by domain type
Aggregated from raw result counts across the provider categories below. Business = G-Suite, Hotmail (Business), Mimecast, Proofpoint, Ionos. Free = Gmail, Yahoo, Hotmail (Free), Apple, Charter. Stress-test addresses excluded from both.
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 98.89% | 0.85% | 0.25% | 0% |
| BounceBan | 96.66% | 3.34% | 0% | 0% |
| Allegrow | 85.85% | 8.14% | 6.01% | 0% |
| Bouncer | 80.83% | 0.75% | 17.19% | 1.23% |
| Emailable | 60.93% | 0.93% | 35.90% | 2.24% |
| AtData | 54.30% | 5.05% | 39.97% | 0.68% |
| KickBox | 49.62% | 0.53% | 30.25% | 19.60% |
| Email Oversight | 46.11% | 0.83% | 28.24% | 24.80% |
| NeverBounce | 28.02% | 0.55% | 24.17% | 47.26% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 98.07% | 1.91% | 0.02% | 0% |
| Bouncer | 94.64% | 0.32% | 0.91% | 4.13% |
| Email Oversight | 89.14% | 1.75% | 0% | 9.06% |
| AtData | 89.14% | 0.75% | 10.20% | 0% |
| KickBox | 85.63% | 1.04% | 10.81% | 2.52% |
| BounceBan | 82.65% | 16.90% | 0.45% | 0% |
| Allegrow | 82.50% | 2.25% | 15.25% | 0% |
| Emailable | 58.12% | 0.07% | 39.09% | 2.68% |
| NeverBounce | 41.04% | 4.57% | 0% | 54.39% |
SECTION 05
Results by mailbox provider
Same benchmark, broken out by individual mailbox provider - including the adversarial stress-test pool.
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 99.86% | 0.07% | 0.07% | 0% |
| BounceBan | 99.59% | 0.41% | 0% | 0% |
| Bouncer | 98.37% | 1.36% | 0.07% | 0.20% |
| Allegrow | 92.71% | 6.40% | 0.89% | 0% |
| AtData | 75.61% | 4.84% | 19.55% | 0% |
| Emailable | 65.40% | 0.95% | 33.65% | 0% |
| KickBox | 64.92% | 0.82% | 34.26% | 0% |
| Email Oversight | 63.56% | 1.43% | 34.95% | 0.07% |
| NeverBounce | 61.99% | 0.54% | 33.11% | 4.36% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 99.69% | 0.31% | 0% | 0% |
| BounceBan | 97.05% | 2.95% | 0% | 0% |
| Allegrow | 84.44% | 1.63% | 13.94% | 0% |
| Bouncer | 74.77% | 0.41% | 22.99% | 1.83% |
| KickBox | 73.45% | 0% | 1.63% | 24.92% |
| Email Oversight | 72.74% | 0.10% | 23.30% | 3.87% |
| Emailable | 72.33% | 0.51% | 27.16% | 0% |
| AtData | 53.10% | 10.27% | 33.88% | 2.75% |
| NeverBounce | 8.24% | 0.31% | 3.76% | 87.69% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 97.31% | 1.08% | 1.61% | 0% |
| BounceBan | 92.29% | 7.71% | 0% | 0% |
| Emailable | 88.71% | 2.15% | 0.36% | 8.78% |
| Bouncer | 86.38% | 0.36% | 8.60% | 4.66% |
| Allegrow | 86.02% | 13.98% | 0% | 0% |
| AtData | 19.35% | 0.54% | 80.11% | 0% |
| KickBox | 16.31% | 0.36% | 1.97% | 81.36% |
| Email Oversight | 10.57% | 0.54% | 0% | 88.89% |
| NeverBounce | 1.43% | 0.18% | 0% | 98.39% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 97.39% | 2.61% | 0% | 0% |
| BounceBan | 94.20% | 5.80% | 0% | 0% |
| Allegrow | 74.89% | 15.34% | 9.77% | 0% |
| Bouncer | 52.84% | 0.45% | 46.48% | 0.23% |
| AtData | 37.95% | 2.84% | 59.20% | 0% |
| KickBox | 21.48% | 0.57% | 76.59% | 1.36% |
| Emailable | 19.66% | 0.57% | 75.23% | 4.55% |
| NeverBounce | 11.93% | 1.14% | 49.89% | 37.05% |
| Email Oversight | 5.00% | 0.80% | 43.41% | 50.68% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| Bouncer | 100% | 0% | 0% | 0% |
| ZeroBounce | 98.90% | 1.10% | 0% | 0% |
| BounceBan | 95.60% | 4.40% | 0% | 0% |
| AtData | 95.60% | 1.10% | 3.30% | 0% |
| Allegrow | 95.60% | 1.10% | 3.30% | 0% |
| Emailable | 94.51% | 1.10% | 4.40% | 0% |
| Email Oversight | 92.31% | 1.10% | 0% | 6.59% |
| KickBox | 21.98% | 2.20% | 0% | 75.82% |
| NeverBounce | 12.09% | 0% | 0% | 87.91% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 99.77% | 0.23% | 0% | 0% |
| Allegrow | 99.77% | 0.23% | 0% | 0% |
| BounceBan | 99.55% | 0.45% | 0% | 0% |
| AtData | 99.55% | 0.68% | 0% | 0% |
| Bouncer | 99.09% | 0% | 0% | 0.91% |
| Email Oversight | 98.87% | 0.68% | 0% | 0% |
| NeverBounce | 98.87% | 0.68% | 0% | 0.45% |
| KickBox | 98.19% | 1.81% | 0% | 0% |
| Emailable | 98.19% | 0% | 1.36% | 0% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 97.61% | 2.39% | 0% | 0% |
| Bouncer | 96.87% | 0.68% | 2.46% | 0% |
| Email Oversight | 87.66% | 1.72% | 0% | 10.62% |
| AtData | 71.58% | 0.86% | 27.56% | 0% |
| KickBox | 69.61% | 1.23% | 29.16% | 0% |
| Allegrow | 58.93% | 1.72% | 39.35% | 0% |
| BounceBan | 55.25% | 43.52% | 1.23% | 0% |
| NeverBounce | 52.61% | 12.09% | 0% | 35.30% |
| Emailable | 0% | 0% | 100% | 0% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| AtData | 99.24% | 0.76% | 0% | 0% |
| ZeroBounce | 98.93% | 1.07% | 0% | 0% |
| BounceBan | 97.98% | 2.02% | 0% | 0% |
| Bouncer | 97.98% | 0.19% | 0% | 1.83% |
| Allegrow | 97.67% | 2.33% | 0% | 0% |
| Emailable | 94.58% | 0.19% | 4.60% | 0.63% |
| KickBox | 92.63% | 0.32% | 0.06% | 6.99% |
| Email Oversight | 84.18% | 1.70% | 0% | 14.11% |
| NeverBounce | 29.99% | 0.06% | 0% | 69.94% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| BounceBan | 100% | 0% | 0% | 0% |
| AtData | 100% | 0.43% | 0% | 0% |
| KickBox | 98.27% | 1.73% | 0% | 0% |
| Email Oversight | 97.11% | 2.60% | 0% | 0.29% |
| ZeroBounce | 95.95% | 3.90% | 0.14% | 0% |
| Allegrow | 91.08% | 4.46% | 4.46% | 0% |
| Bouncer | 86.27% | 0% | 0% | 13.73% |
| Emailable | 82.80% | 0% | 1.59% | 15.61% |
| NeverBounce | 3.18% | 0% | 0% | 96.82% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 100% | 0% | 0% | 0% |
| BounceBan | 98.15% | 1.85% | 0% | 0% |
| Email Oversight | 98.15% | 1.85% | 0% | 0% |
| AtData | 98.15% | 1.85% | 0% | 0% |
| KickBox | 98.15% | 1.85% | 0% | 0% |
| Emailable | 96.30% | 0% | 3.70% | 0% |
| Allegrow | 96.30% | 3.70% | 0% | 0% |
| NeverBounce | 29.63% | 0% | 0% | 70.37% |
| Bouncer | 0% | 0% | 0% | 100% |
| Tool | Accurate | Inaccurate | Failed to Validate (Catch-All) | Unknown |
|---|---|---|---|---|
| ZeroBounce | 95.59% | 1.25% | 3.16% | 0% |
| Emailable | 74.57% | 2.64% | 15.42% | 6.92% |
| Allegrow | 70.72% | 13.55% | 15.73% | 0% |
| Email Oversight | 69.10% | 14.49% | 6.06% | 7.64% |
| BounceBan | 68.18% | 30.76% | 0% | 0.92% |
| Bouncer | 64.10% | 10.14% | 7.71% | 18.05% |
| AtData | 45.06% | 19.89% | 18.71% | 16.07% |
| KickBox | 43.57% | 14.17% | 6.99% | 35.27% |
| NeverBounce | 29.78% | 10.28% | 14.30% | 45.65% |
SECTION 06
Methodology
The test list. 9,901 real-world addresses deliberately drawn from the domain pools that are notoriously hardest to validate: security-gatewayed business domains (Mimecast, Proofpoint), catch-all-heavy business hosting (G-Suite, Hotmail Business, Ionos), major consumer providers (Gmail, Yahoo, Apple, Hotmail Free, Charter), plus a stress-test pool of malformed addresses, bad characters, duplicates, special formats, and hard-to-validate cases. This is not a random sample of everyday lists - it is deliberately adversarial. Most tools score higher on easy lists; this benchmark measures what happens on the lists that actually cause bounces.
Ground truth. Where all tools agreed and no evidence contradicted them, the consensus verdict stood. Every address where tools returned conflicting verdicts was manually verified by ZeroBounce deliverability engineers, using SMTP-level evidence, to establish which verdict was correct.
Category definitions. Every tool reports results in its own status taxonomy (valid/invalid, deliverable/undeliverable, risky, accept-all, and so on). To compare tools fairly, each tool's verdict for each address was mapped to one of five categories against ground truth:
| Category | Definition |
|---|---|
| Accurate | The tool's verdict matched ground truth. A deliverable address was called valid, or an undeliverable address was called invalid. |
| Inaccurate | The tool's verdict contradicted ground truth. A deliverable address was called invalid, or an undeliverable address was called valid. |
| Failed to Validate (Catch-All) | The tool returned "catch-all," "accept-all," or an equivalent non-committal status for an address that ground truth shows is resolvable to valid or invalid. The tool wasn't wrong - it simply didn't produce an answer where one exists. |
| Unknown | The tool returned "unknown," "unverifiable," or an equivalent status - no verdict at all. |
| Missing | The tool returned no result for the address: processing failure, dropped row, or an address the tool refused to accept. |
Test execution
All tests were conducted in the last two weeks of July 2026. Each tool was tested via its standard paid product, on the same list, with no special configuration.
Known limitations
Self-conducted; snapshot in time (July 2026) - mailbox providers change behaviour continuously; the test list is deliberately adversarial, so scores here will be lower than on typical customer lists for every tool tested.
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