Email verification

Email verification is the process of finding out whether an email address can actually receive mail before you send to it. A verifier typically runs a series of checks, from cheap to expensive: is the syntax valid, does the domain exist, does it publish MX records, and does the receiving mail server accept the specific mailbox?

The last step is the important one. The verifier opens an SMTP conversation with the domain's mail server, announces a recipient with the RCPT TO command and reads the reply. A 250 reply means the server accepted that recipient; a 550 reply usually means the mailbox doesn't exist. The verifier then ends the session before the DATA command, so no message is ever sent.

Verification can't always give a yes or no. A catch-all domain accepts every address, so a single mailbox can't be confirmed, and servers that time out, greylist or rate-limit return no definitive answer. That's why good verifiers report more than two outcomes, such as valid, risky, invalid and unknown.

Every address that doesn't exist becomes a hard bounce when you send to it. Bounces waste sends, and mailbox providers treat repeated delivery attempts to nonexistent addresses as a sign of poor list quality, which can hurt your sender reputation and push future emails toward spam.

For outbound teams this matters most right before a campaign: lists built weeks ago and old CRM exports contain addresses that have gone stale.

Skrap.ai is an email verifier and email finder. The verifier checks syntax, domain and MX records, runs a mailbox check over SMTP without sending an email, and detects catch-all domains. Every result is Valid, Risky, Invalid or Unknown, and you pay 1 credit only for Valid or Risky results: Invalid and Unknown are free. Try a single address with the free email verifier, upload a CSV, or use the API docs and the Google Sheets add-on. See pricing for credit plans and email verification best practices for a workflow.