SMTP Verify
Lookups
SMTP Verify
Dedicated real-time SMTP deliverability check for a single email address.
POST
SMTP Verify
Overview
POST /api/smtp/verify runs a fast, real-time SMTP deliverability check on one
email address. It answers a single question: can this mailbox receive mail. It
does not run the full validity report (domain trust, person footprint, breach
signals). Use it when you only need the mailbox verdict, for example inline on a
signup form or during list cleaning.
The check performs a live MX and SMTP probe and typically responds in under
200ms.
Authentication
Works with an API key or an in-app session. For API access, pass your key in theAuthorization header.
Request
The email address to verify.
Example request
Response
The email address that was checked (normalized to lowercase).
The mailbox verdict:
valid, invalid, catch_all, accept_all,
temporary_failure, blocked, timeout, or unknown.true when mail can likely be delivered to this address.true when the recipient mailbox was confirmed to exist.true when the domain accepts any recipient, so the specific mailbox cannot
be proven over SMTP.The mail server (MX host) used for the probe.
true when the address uses a disposable or throwaway provider.true when the local part is a role or shared mailbox (for example support@
or info@).A suggested correction when a likely typo is detected. Omitted when there is
no suggestion.
RFC 3339 timestamp of when the check ran.
Credits charged for this request (
1, or 0 for a free repeat within the
billing window).Example response
Billing
This endpoint charges 1 credit per verification. Repeat checks of the same address are free for 6 months. That free window is shared with Email Validity, so a customer who has already verified an address on either endpoint is not charged twice.For the full deliverability report (domain trust, person footprint, breach and
disposable signals), use
Email Validity instead. SMTP Verify
returns only the mailbox verdict.