mailbox existence check api
Mailbox existence check API
Ask whether a mailbox appears to exist without sending a message to the user.
Mailbox existence checks are a higher-confidence signal than syntax or domain checks.
They are best used after disposable and domain checks have passed.
You should treat the result as a signal, not a guarantee.
220 mail.example.com ESMTP
EHLO emailverify.se
MAIL FROM:<[email protected]>
RCPT TO:<[email protected]>
QUITWhy not send mail?
A check API lets you reduce friction and avoid user-facing spam.
Where does it fit?
Use it during signup, lead capture, and account recovery flows.
What SMTP probing actually proves
SMTP probing is a protocol conversation with the recipient domain. It can indicate whether a mailbox appears to accept mail, but it also reflects server policy, temporary throttling, anti-abuse behavior, and catch-all handling.
How to use it safely
Keep probing on the server, add timeouts, respect provider limits, and avoid repeated retries against the same domain. In production, you should store only the resulting status and score, not the full transcript.
FAQ
How do I use this page?
Use it as a quickstart reference and link it from your docs, onboarding flow, or marketing page.
What should I do next?
Create an account, try the demo, and move the integration into your backend with a real API key.
Can SMTP confirm the owner is real?
No. It only suggests that the mailbox path looks reachable at the time of the check.
Why not send a message instead?
Because many products need a quiet validation path before onboarding or import completes.