smtpprobe.com

If you found this name in your mail server's logs: 5.11.83.252 is a verification prober. It checks whether a mailbox exists on behalf of the person who typed the address, and it never delivers mail.

What a probe looks like

• One SMTP connection, then MAIL FROM and RCPT TO.
• QUIT before DATA — no message body is ever sent.
• Rate-limited per destination, and the result is cached, so the same address is not asked about twice in a short window.

If you would rather not receive them

Write to abuse@smtpprobe.com and the domain will be added to the do-not-probe list.