This tool verifies an email address through multiple steps: syntax check, domain existence, MX records, and SMTP verification — without sending an actual email.
Many major providers (Gmail, Outlook, Yahoo, Mail.ru) use catch-all or block VRFY/RCPT to protect privacy. A 250 response does not guarantee the mailbox exists; a 550 does not guarantee it doesn't.
No, our service is completely safe. We connect to the recipient's mail server, send only the RCPT TO command and disconnect before transmitting any message body. Mail providers do not treat this as a spam attempt — the SMTP handshake is standard routing behaviour. Your IP will not be blacklisted.
Large providers use protective mechanisms that either block SMTP probes from unknown senders or deliberately respond "250 OK" to every address to prevent spammers from harvesting valid mailboxes. In such cases the tool correctly shows "Undetermined" and recommends indirect methods such as checking data breach records or sending a real double opt-in message.
The optimal interval is every three to six months. Over that time some addresses become inactive, and others may turn into spam traps. For transactional mailings such as order notifications, verify addresses right before sending. Regular verification keeps your bounce rate low and maintains a strong sender reputation.