Verify an email address
Paste an address and get syntax, MX, SPF and DMARC, disposable-provider and role-account signals in about a second. No signup, no card. It runs the same engine as the API.
What it checks
- Syntax
- Whether the address is well-formed. Catches the typos that never had a chance of delivering.
- MX records
- Whether the domain publishes mail exchangers at all. A domain with no MX cannot receive mail from anyone, which is a hard stop rather than a risk score.
- SPF and DMARC
- Whether the domain publishes sender-authentication policy. Its absence says something about how the domain is run.
- Disposable providers
- Matched against a curated list of throwaway-inbox providers, backed up by catch-all heuristics for the ones that rotate domains faster than any list can follow.
- Role accounts
- Addresses that reach a function rather than a person — support@, billing@, noreply@ and around forty more. These behave differently in a signup funnel and in a cold sequence.
- Catch-all detection
- Whether the domain accepts everything at the MX layer, which is precisely the case where per-mailbox certainty is unavailable to anyone.
- Free providers
- Whether the address belongs to a consumer mailbox provider rather than a company domain. Not a problem in itself — it is a fact about who you are talking to, and it changes what a B2B signup means.
- Blacklist status
- Whether the sending domain appears on the reputation lists that receiving servers consult.
What no verifier can tell you
This one included. We check the domain: whether it can receive mail, how it is configured, and whether it belongs to a throwaway provider. We do not check whether the specific mailbox exists. Doing that means connecting to someone else's mail server and asking, which our serverless infrastructure cannot do — outbound port 25 is blocked — and which would be an unreliable answer even if it could: catch-all domains say yes to everything, greylisting makes the reply slow and ambiguous, and at volume the probing IP gets blocked.
The practical consequence: an address can come back clean here and still bounce, because the company kept the domain and retired the person. Treat the result as a filter that removes what was never going to work, not as a guarantee about what will. The only proof of delivery is delivery.
Questions
Does this confirm the mailbox exists?
No. We do not run an SMTP mailbox probe, for two reasons and we would rather state both. The first is a constraint: we run on serverless infrastructure where outbound port 25 is blocked, so the probe is not available to us. The second is that we would be cautious about it anyway — catch-all domains answer yes to everything, greylisting makes the answer slow and ambiguous, and probing at volume damages the reputation of the IP doing the probing. So we grade on syntax, MX, SPF/DMARC and disposable/role signals: what can be established without touching the recipient's server. Any verifier claiming per-mailbox certainty on a catch-all domain is claiming something nobody can know.
So what is it actually good for?
Filtering. It removes the addresses that were never going to deliver — malformed, no MX, throwaway providers — and it flags the ones that behave differently even when they do deliver, like role accounts. On a signup form that is most of the value. On a cold list it is the difference between a bounce rate that damages your sending domain and one that does not.
Why does a valid-looking address sometimes bounce anyway?
Because the domain is fine and the mailbox is not. A company can have perfect MX, SPF and DMARC and still have retired the individual address you hold. That gap is inherent to checking without sending. The only proof of delivery is delivery.
Is there a limit?
The public checker is rate-limited per IP and protected against automated scraping. A free API key gives you 100 verifications a month with no card, which is the sensible next step if you want to check a list rather than an address.
Do you store the address I check?
The public checker does not create an account or a record you have to manage. See the privacy policy for the detail.
Checking a list, not an address?
A free key gives you 100 verifications a month with no card, and the bulk endpoint takes a whole list in one call.