Email Verification Benchmark 2027: 6 Tools, 1,000 Emails

TL;DR

• WizLeads approved 852 of the 1,000 addresses, and 5 bounced (0.59%). Of the three tools that approved more than 800, it had the lowest bounce rate.
• ZeroBounce approved the most, 888, but bounced at 3.72% against WizLeads' 0.59%, a rate 6.3 times higher.
• LeadMagic came closest to WizLeads: 822 approved and 7 bounces (0.85%), at a higher price per check.
• NeverBounce, MillionVerifier and Debounce kept bounces between 0.15% and 0.99% by rejecting 289, 291 and 330 addresses, 28.9% to 33.0% of the list.
• Two tools paired a low bounce rate with a small rejection count: WizLeads and LeadMagic.

Verifiers sell on accuracy figures that a buyer cannot check. We wanted figures we could check. So we ran one list of 1,000 real-estate decision-maker emails through six verifiers on the same day. Then we sent a test email to every address each tool approved and counted the bounces.

This page gives two numbers for every tool: how often its approvals bounced, and how much of the list it rejected. Every test figure comes from the raw data at the bottom of the post.

How did the six verifiers score?

Valid is what a tool approved. Rejected is every address it did not mark valid, whatever the label.

On 1,000 addresses, the gap between 4 bounces and 7 is noise. So the five tools with single-digit bounces cannot be ranked against each other on bounce rate. The one gap the data supports is ZeroBounce's 33 bounces against single digits for the other five.

How did we run the test?

The source list was 1,000 decision-maker emails for US real-estate agencies, exported from Apollo in April 2026. All six providers got the same CSV on the same day, within a two-hour window. None of them knew the list was a benchmark.

Next, we took the addresses each tool approved as valid. We sent a plain-text test message to each one from a clean Google Workspace account. Addresses that no tool approved were never mailed. Over 72 hours, we counted hard bounces and mailbox-does-not-exist replies. Soft bounces that cleared inside the window did not count.

The sending account had never mailed any domain on the list. So each bounce reflects whether the mailbox exists. Filtering based on the sender's reputation played no part.

Why test on a real-estate list?

Real-estate decision-makers are a hard test for email verification. Many agency domains are catch-alls: the domain accepts mail for every address, whether or not the mailbox exists. On such a domain, a basic server check cannot tell a real mailbox from a made-up one.

WizLeads detected 212 catch-all addresses (21.2% of the sample) and 159 behind a Secure Email Gateway (15.9%). Both counts come from WizLeads' classifier. No other source gives the list's true make-up, so treat them as one tool's reading of the list. Together that is 371 addresses, 37.1% of the list, sitting in the difficult-to-verify category.

On a Fortune 500 list, catch-alls would be rarer and the gaps between tools would shrink. A typical small-business B2B list looks much closer to this one.

Which verifiers resolve catch-all addresses?

To resolve a catch-all, a tool must decide valid or invalid for an address the server would accept anyway. That step is the core of catch-all email verification. In our run, three tools did it and three did not.

The three that flag catch-alls each use a different label, so the verdicts do not line up across vendors. An unresolved flag is not an approval. That is why NeverBounce, MillionVerifier and Debounce land between 670 and 711 valid, while the other three sit between 822 and 888.

In this benchmark, catch-all handling mattered more than any other factor. If more than 10% of your list sits on catch-all domains, picking a tool that resolves them decides whether you can mail most of your list or lose about a third of it to rejections.

How did each verifier do?

WizLeads

852 valid, 5 bounces (0.59%), 148 rejected.

WizLeads, ZeroBounce and LeadMagic each kept more than 800 addresses, and WizLeads bounced least of the three. Among the five tools under 1%, it rejected the fewest. Its catch-all and SEG handling is what makes that pairing possible. WizLeads flagged 212 catch-all addresses and resolved every one into valid or invalid, so none landed in a "risky" pile for you to sort.

It also found 159 addresses behind a Secure Email Gateway and named the gateway for each one: Proofpoint, Barracuda, Mimecast, Appriver or Sophos.

Best for: cold email teams that cannot afford known bounces or the loss of about a third of a list to rejections.

ZeroBounce

888 valid, 33 bounces (3.72%), 112 rejected.

ZeroBounce approved the most emails in the test, 36 more than WizLeads. But 33 of its approvals bounced. Most of those bounces followed one pattern in our test set: ZeroBounce marked addresses on Google catch-all domains as valid, and the mailbox turned out not to exist when we sent to it. This is what we observed on this list. It is not a claim about how ZeroBounce's validation works internally, which a send test cannot show.

Best for: teams that put list volume ahead of deliverability risk. In our test, that volume came with a 3.72% bounce rate on one list of 1,000 real-estate decision-maker emails. If your lists look like ours, check that your domains can absorb a rate like that.

LeadMagic

822 valid, 7 bounces (0.85%), 178 rejected.

LeadMagic came closest to WizLeads on accuracy. It also resolves catch-alls instead of leaving them in a risky bucket, and a 0.85% bounce rate is fine for cold email. But at today's prices, LeadMagic's entry plan costs about 2.5x as much per verification as WizLeads' entry plan, and that adds up fast in a 100K-lead month.

The other gap is rejections: LeadMagic rejected 178 addresses to WizLeads' 148. On a 10,000-lead campaign, that gap grows to a few hundred more leads off the list.

Best for: teams already on LeadMagic who are fine with the cost. If price matters at your volume, test the same list against WizLeads before you renew.

NeverBounce

711 valid, 4 bounces (0.56%), 289 rejected, 79 of them unknown.

NeverBounce's bounce rate was slightly lower than WizLeads': 0.56% against 0.59%. But it rejected 289 addresses to WizLeads' 148, and 79 of those came back "unknown". That is 7.9% of the list you paid to verify and still cannot send to.

Most of the gap comes from its catch-all handling. NeverBounce flags catch-alls as "catchall" and does not resolve them. Those 137 flags and the 79 unknowns all sit inside its 289 rejections. On a list where 21% of addresses sit on catch-all domains, NeverBounce rejected 141 more addresses per 1,000 than WizLeads did.

Best for: compliance-heavy teams, where shipping a single bad email costs more than losing another 14% of the list to rejections.

MillionVerifier

709 valid, 7 bounces (0.99%), 291 rejected, 170 of them flagged as catch_all.

MillionVerifier's results have almost the same shape as NeverBounce's: few bounces and many rejections. MillionVerifier flags catch-alls without saying whether they are valid or invalid; its 170 catch_all flags stayed unresolved in our run. That is why it lands at 709 valid on a list with this many catch-alls.

Its pricing is competitive at volume. Its credits do not expire, which helps if you verify in irregular bursts, though its Terms carry an inactivity clause. Be aware that on this B2B list, heavy with catch-alls, it rejected about a third of the addresses.

Best for: users already invested in MillionVerifier who can absorb the trade-off, especially on lists with few catch-alls.

Debounce

670 valid, 1 bounce (0.15%), 330 rejected, 201 of them flagged as Accept All.

Debounce had the lowest bounce rate of the six: 1 bounce in 670 approved sends. In exchange, it did not approve 330 addresses, the most of any tool we tested. Our run used its standard check, without its paid catch-all check.

The 670 it approves are clean. But a third of the list is gone to rejections, and its 201 Accept All flags come back to you to sort out.

Best for: senders who guard their reputation above everything, or teams that accept a smaller validated pool in exchange for near-zero bounce risk.

Which verifiers detect secure email gateways?

A Secure Email Gateway (SEG) is a filter that sits in front of a company's inbox. Proofpoint, Mimecast, Barracuda, Appriver and Sophos are five common ones. A gateway can answer a verification check differently from the mailbox behind it, and that is where a verifier can return a false valid on a protected domain.

In our list, 159 addresses (15.9% of the sample) sat behind one of these five.

WizLeads named the gateway for each of those 159 addresses. LeadMagic's validation API returns gateway fields of its own, and its mx_gateway field names the gateway vendor. ZeroBounce's homepage says it validates addresses protected by SEGs. The API docs of NeverBounce, MillionVerifier and Debounce list no gateway field, and their results in our run said nothing about the gateway.

This matters in B2B because SEG-protected mailboxes usually belong to mid-market and enterprise buyers, the most valuable targets on a list. When a gateway address comes back as a plain "valid" or "risky", you lose the chance to route it differently or to warm up the sending domain first.

Is the lowest bounce rate the best result?

No. Bounce rate alone does not pick the best tool. You need two numbers together:

1. Bounce rate: how often a "valid" verdict bounces when you send.
2. Rejection rate: how much of the list a tool refuses to pass, whatever the reason.

Most comparison posts publish only the first. That leaves out a real cost: a tool can buy a clean bounce rate by refusing more of your list.

Our test counted how much each tool rejected. Grading those rejections as right or wrong would mean mailing every address a tool rejected, and this run mailed only addresses that at least one tool approved. Read a rejection count as the cost side of the trade. It is no proof of error.

On both numbers, the six split like this:

• Debounce: 0.15% bounce, 330 rejections. The lowest bounce rate came with the most rejections.
• NeverBounce and MillionVerifier: 0.56% to 0.99% bounce, 289 to 291 rejections. The same shape.
• ZeroBounce: 3.72% bounce, 112 rejections. The reverse trade.
• WizLeads: 0.59% bounce, 148 rejections, the fewest rejections of the five tools under 1%.
• LeadMagic: 0.85% bounce, 178 rejections. Second on this pair of numbers, with the price gap noted above.

Finding addresses comes before verifying them. We measured that step in the email enrichment benchmark, on a separate 1,000-lead list: which finder returns the most addresses that then pass verification.

Which verifier should you pick?

Pick by what you need most:

• The lowest bounce rate, with a smaller validated pool: Debounce (0.15% bounce, 670 valid) or NeverBounce (0.56% bounce, 711 valid). Expect 28.9% to 33.0% of your list to be rejected.
• The most validated volume: ZeroBounce (888 valid, 3.72% bounce in our test). That rate comes from one 1,000-address list heavy with catch-alls. It is not a rate ZeroBounce publishes, and your lists may differ. If you see a bounce rate like that on your own sends, watch sender reputation closely and spread volume across sending domains. Mailbox providers publish no bounce threshold. The written limits come from sending platforms, such as Mailgun's 5% and Postmark's 10%. If that rate is too high for you, each of the other five tools here bounced less, and there are more ZeroBounce alternatives beyond this test.
• Low bounces and a large valid pool on a B2B list with many catch-alls: WizLeads (0.59% bounce, 852 valid). LeadMagic (0.85% bounce, 822 valid) is the closest option if its higher price per check is fine for you.
• An existing MillionVerifier workflow and lists with few catch-alls: stay on MillionVerifier. The few-catch-alls part matters. On B2B decision-maker lists, the trade-off is worse.

If your choice is ZeroBounce vs NeverBounce, this test shows opposite trades: ZeroBounce approved 888 addresses and 33 bounced, while NeverBounce approved 711 and 4 bounced.

Can you trust a verifier's accuracy claim?

Not on its own. The usual way to pick a verifier is to read the accuracy claim on the vendor's homepage. ZeroBounce advertises 99.6% accuracy. NeverBounce promises over 98% deliverability. MillionVerifier's 99.9% is an uptime figure, not an accuracy one. The three figures look alike, but they measure three different things. On the same list, the tools behind them gave very different results: ZeroBounce bounced 33 emails, and NeverBounce rejected 289 addresses.

So run your own test before you commit. A 1,000-email test on your own type of list takes about two hours of work, spread over four days. It settles more questions than six months of reading vendor pages would.

Reproduce this test on your own list

The same send test works on any verifier, so you can run it on tools from the ranked list of email verification tools as well as these six. To run it on your own type of list:

1. Pick a sample of 500 to 1,000 emails from the type of list you send to. B2B decision-maker lists have different catch-all rates from consumer or freelancer lists.
2. Run the same CSV through each tool on the same day, ideally within a two-hour window.
3. Separate each tool's "valid" output. Send a plain-text test message to each of those addresses from a clean Google Workspace or Microsoft 365 sender with no history on the target domains.
4. Count hard bounces and mailbox-does-not-exist replies over 72 hours. Do not count soft bounces that clear inside the window.
5. Optional but recommended: send to a sample of each tool's rejected addresses and count how many deliver. This is the false-invalid check most benchmarks skip.

Step 5 is the step this run skipped. Without it, a tool that rejects good addresses can still look like the winner, because its bounce rate stays low.

Download the raw data

The benchmark spreadsheet in Google Sheets holds every email, verdict, bounce and SEG flag from the 1,000-email test. You can open it or download it.

It has two tabs. The Summary tab holds the counts behind the tables on this page. The Raw Data tab has all 1,000 rows, with the WL_Catchall flag, the SEG provider for each address and every verifier's own verdict.