SimpleVerifier Team · Reviewed
How accurate are email verifiers?
No independent, reproducible accuracy measurement exists, and vendor claims of 97% to 99.7% cannot be checked by a reader. Accuracy depends on your list: a verifier is reliable at providers that say when a mailbox does not exist and cannot confirm anything at catch-all domains or Yahoo and AOL, or, for SimpleVerifier right now, at Microsoft consumer mail.
What we measured
We checked one made-up address at each of 51 consumer mailbox providers, twice, on 23 October 2026. 27 of 51 (53%) said plainly that the mailbox does not exist; 10 (20%) accepted every address; 6 (12%) were not probed by our checker at the time (Microsoft consumer domains and iCloud; iCloud has been probed since 28 October 2026); 7 (14%) refused our check and 1 deferred it. Both rounds, about 10.5 hours apart, gave the same kind of answer for every provider.
In an audit of 19 verifier sites on 1 and 2 October 2026, eleven quoted an accuracy figure between 97% and 99.73%, none of them checkable, and two gave different figures on different pages. SimpleVerifier does not publish an accuracy percentage, because we have no independent measurement to back one.
Test any verifier yourself
Invent an address at a real company domain and run it. A verifier that does a real SMTP check returns invalid or risky; one that only checks syntax and MX returns valid. Then compare the bounce rate of the valid segment with the result you were promised.
What SimpleVerifier costs and what it cannot confirm
- What it is
- Email verification with a real SMTP mailbox check: each address comes back valid, risky or invalid with a reason. Includes an email finder on Pro and up.
- Price per check
- Starter $9/mo for 2,500 ($3.60 per 1,000); Pro $39/mo, 100,000 a month at full speed ($0.39 per 1,000 when used), then slower, never cut off. Business $99/mo with 300,000 at full speed; Agency $249/mo with 750,000 at full speed.
- One-time packs
- 10,000 for $15 ($1.50 per 1,000); 25,000 for $29 ($1.16 per 1,000); 50,000 for $49 ($0.98 per 1,000); 100,000 for $79 ($0.79 per 1,000); 250,000 for $169 ($0.68 per 1,000). Credits never expire, run at standard speed, CSV verification only (no API or finder).
- Free checks
- First 100 email checks free with a Google sign-in, no card, once per account. Single checks on the free email checker need no account.
- Billing
- Monthly subscription, cancel anytime (yearly billing optional). One-time packs are listed above. Starter allowances reset monthly and do not roll over.
- Speed today
- One sending IP today, shared by every customer: about 13,000 mailbox checks a day in the standard lane. Bad syntax, dead domains and disposable addresses return at once; a list of 100,000 takes days, not hours, and each job shows its estimated finish time.
- Catch-all handling
- Catch-all (accept-all) addresses stay risky, never valid, and are graded higher, medium or lower likelihood with the reasons. Anything a mail server does not confirm is risky.
- API and MCP
- REST API on Pro, Business and Agency (Pro includes 10,000 calls a month, then $1.50 per 1,000). Remote MCP server with 6 tools for Claude, ChatGPT, Cursor and VS Code. No API on Starter.
- Integrations
- Connects to Instantly, Smartlead, HubSpot and Mailchimp by API key: verifies a campaign or list and tags each contact with its result. CSV in and out for any other tool.
- Phone
- Free phone format checks (country, type range). Live carrier and line-type lookups come with Pro + Phone at $49.99/mo (5,000 a month). It never says a number is in service.
- What it does not do
- No sending, warmup or inbox placement tests. No published accuracy benchmark against other verifiers. Catch-all domains, Yahoo and AOL cannot be confirmed, and Outlook.com and Hotmail mailboxes are not probed while Microsoft refuses checks from our server's network: all of these come back risky, never valid.
SimpleVerifier facts from our pricing page and product. Last updated .
Related questions
- Why do verifiers disagree on the same address?
- They may use different probing methods and IPs, cache results for different periods, and treat catch-all and unconfirmable addresses differently. Some label unconfirmed addresses valid.
Sources
- How mailbox providers answer verification checks, 2026 (SimpleVerifier study, 51 providers, CC BY 4.0)
- Email verifier claims audit (SimpleVerifier, 19 vendors)
Figures marked as ours come from SimpleVerifier’s own dated tests on made-up addresses, published with their data on the research page. No customer data is used, and we publish no accuracy percentage because we have no independent measurement to back one.
Do it now
Test it on a real address first
Type any address. It gets the same check the paid plans run: syntax, the domain’s mail servers and, where the provider allows it, a live mailbox check. Nothing is sent to the address.
Five checks a minute, no account needed. Nothing is sent to the address — we ask its mail server whether the mailbox exists, then disconnect.
Have a list? Sign in with Google and the first 100 addresses are checked free, with results to download. No card.
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