Unknown email result

An unknown verification result means the check couldn't reach a conclusion. The address passed the earlier checks (syntax, domain, MX), but the mailbox check over SMTP didn't return a clear accept or reject.

Common causes: the mail server timed out or refused the connection, it returned a temporary 4xx code (for example because of greylisting or rate limiting), it blocked the verifier's IP address, or it behaves inconsistently from one attempt to the next. Some servers deliberately hide whether mailboxes exist to frustrate address harvesting.

Unknown is different from Risky. A risky result on a catch-all domain is a definite answer (the server accepts everything), while unknown means no answer was obtained.

Unknown addresses are a coin you haven't flipped yet. Sending to them in bulk can raise your bounce rate, while dropping them all may discard good contacts. A practical approach is to re-check unknowns later, since temporary conditions often clear, and to keep any that remain unknown out of your first sends to a new domain.

Skrap.ai reports these addresses as Unknown, and Unknown results are free: you only pay a credit for Valid or Risky results. You can re-check them later in the free email verifier or through the API without having paid for the first inconclusive attempt.