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§ READING THE RESULT
What each answer actually means.
Most checkers give you a green tick or a red cross and hide everything in between. The in-between is where the money is, so we name it.
Valid
The receiving server confirmed this specific mailbox exists. Safe to send — this is the only result that means the address is genuinely deliverable.
Keep it.
Invalid
The mailbox does not exist, the domain has no mail servers, or the address is malformed. Sending to it produces a hard bounce.
Remove it before your next send.
Risky
We reached the server but it would not confirm the mailbox — usually a catch-all domain or a provider that blocks verification. Nobody can resolve these addresses; we say so instead of guessing.
Send only if you can absorb a bounce.
Disposable
A flag, not a verdict — it can appear alongside any of the three above. The mailbox may work right now but belongs to a throwaway service and will vanish within hours.
Treat as low value regardless of validity.
§ HOW IT WORKS
Five checks behind one answer.
Syntax check
Is the address even a legal email address? Catches typos, stray spaces and malformed domains before any network call.
Domain & MX lookup
Does the domain exist, and does it publish mail servers? A domain with no MX records cannot receive email at all.
SMTP handshake
We open a conversation with the receiving server and ask whether it would accept mail for this exact mailbox — then disconnect without sending.
Catch-all test
Some domains say yes to every address. We probe with a random mailbox to detect that, so a meaningless yes is never reported as Valid.
Disposable detection
We match the domain and its MX hosts against 12,000+ known throwaway providers, so temp-mail addresses are flagged even when they verify clean.
Answers in seconds
The full pipeline runs in parallel — a single address resolves in a couple of seconds.
Stealth checks
No email is ever delivered and the mailbox owner is never notified.
Honest Risky label
Unverifiable addresses are labelled unverifiable, not quietly counted as valid to flatter a score.
§ WHEN TO USE IT
Worth checking before you send.
Validating a signup
Someone just typed an address into your form. Check it before you write the row, and you never chase a confirmation email that cannot arrive.
Before a cold outreach send
One bad address in a small sequence is a wasted slot. One bad address in a thousand is a reputation problem. Check the risky ones first.
Auditing an old list
Lists decay around 2% a month. Spot-check a sample here; if the failure rate is ugly, run the whole file through the bulk verifier.
Checking a lead you were given
A scraped or purchased address is worth checking before it touches your ESP, where every dead contact costs you on every send.
§ THE PRIMER
What does it mean to check an email address?
Checking an email address means answering one question: if I send mail here, will it arrive? That is a different question from whether the address looks right. Plenty of addresses that pass a regex — [email protected] — belong to nobody at all, because John left two years ago and the mailbox was deleted.
The only authority on whether a mailbox exists is the server that hosts it. So a real check has to ask that server. Our pipeline resolves the domain's MX records, connects to the highest-priority mail server, and walks through the opening moves of an SMTP conversation — the same moves a real sending server makes — up to the point where the receiving server says whether it would accept mail for that recipient. Then we hang up. Nothing is delivered, and the mailbox owner sees nothing.
Two situations break that clean answer, and honest tooling admits it. A catch-all domain is configured to accept mail for every possible address, so its yes carries no information. And some large providers deliberately refuse to confirm or deny mailboxes, precisely to stop this kind of probing. In both cases the truthful output is “cannot be determined” — which is what our Risky result means. A service that reports those as Valid is inflating its own accuracy figures with your bounce rate.
Finally, validity is not the same as value. A disposable address from a temp-mail service is a real, working mailbox at the moment you check it, and a dead one an hour later. That is why disposable detection is a separate flag here rather than a verdict: you may want to accept a risky address from a real company and reject a perfectly valid one from a throwaway provider.
§ FAQ
Email checker FAQ
How the check works, what it can and cannot tell you, and where the free limits sit.
Still have questions? Contact us§ ONE ADDRESS OR ONE MILLION
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