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The Email Validation API tells you whether an address is deliverable. It finds the mail server for the address’s domain and asks it, over SMTP, whether it would accept mail for that address. No email is sent. Use it to:
  • reject mistyped or made-up addresses at signup;
  • clean a mailing list before a campaign;
  • check an address before you rely on it for password resets or notifications.

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How a check works

1

Format

The address must contain an @. Otherwise the result is invalid_format and nothing else happens.
2

Mail server lookup

validate.al looks up the domain’s MX records and picks the highest-priority server. A domain that doesn’t exist returns domain_not_found; a domain without MX records returns no_mx_records.
3

SMTP probe

validate.al connects to that server on port 25, introduces itself and asks whether the server accepts mail for the address (RCPT TO). It then disconnects without sending anything. If the server answers 250, the result is true; any other answer is false.
Each check makes one connection to the recipient’s mail server, so a result can take up to about 10 seconds when that server is slow.

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What a result means

  • true: the mail server accepted the address. That’s the strongest signal SMTP gives, but some servers accept every address (catch-all domains), so true doesn’t prove a mailbox exists.
  • false: the mail server refused the address. This usually means the mailbox doesn’t exist, but some servers refuse all verification attempts or temporarily reject unknown senders.
  • A text status: the check couldn’t reach a verdict. See Results for each value.

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Next steps

Quickstart

Make your first request in a minute.

API reference

The endpoint, request and response in full.