Kluno cleans your list against a 12-layer engine: real SMTP checks, provider-aware logic, catch-all and role detection. When an address genuinely can't be confirmed, we say unknown instead of guessing "valid" to pad our numbers.
One engine, many ways to use it. Verify a single address, drop in a CSV, or wire the API into Clay and your existing stack.
We open a live conversation with the receiving mail server, not a database lookup. That's what separates a real check from a guess.
Microsoft 365, Google Workspace, and Gmail each behave differently. Kluno reads each provider on its own terms instead of one blunt rule.
Flags catch-all domains, role accounts (info@, sales@), disposable inboxes, and likely spam traps, the addresses that quietly hurt deliverability.
Catches gmial.com-style mistakes and suggests the intended address, so you recover leads instead of dropping them.
A clean REST API with per-key auth, a Clay-ready HTTP column, and bulk CSV upload in the dashboard. Fits the workflow you already run.
When a mailbox genuinely can't be confirmed, we tell you. No inflated "valid" rate that blows up in your bounce report two weeks later.
Most "verifiers" match your address against a stale list of known-good and known-bad. Kluno actually checks. Every layer runs on every address.
Roughly half of all business email runs on Microsoft 365, which deliberately answers "OK" to every address to stop attackers from mapping a company's mailboxes. No verifier on earth can confirm those with certainty.
Competitors hide this. They stamp those addresses "valid" (or bury them as "catch-all") so their accuracy number looks better. Kluno tells you the truth: unknown. You decide whether to send, and your bounce rate stays honest.
Every verifier hits the same physics ceiling on Microsoft 365. The difference is whether they admit it.
| Kluno | Typical verifier | |
|---|---|---|
| Real live SMTP checks | Yes | Sometimes |
| Returns an honest "unknown" | Yes | No, guesses "valid" |
| Provider-aware (M365 / Google) | Yes | Partial |
| Catch-all & role flagging | Yes | Yes |
| Inflated accuracy marketing | Never | "99%+" |
| API + Clay + CSV | Yes | Varies |
?key= or an x-api-key header. Full details are in the API docs.Start free with 500 verifications a month, no credit card. Bring your own list and see the difference an honest verdict makes.