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Free active SMTP probe

See whether your real MX servers protect mail in transit.

Resolve the delivery route, connect safely to port 25, negotiate STARTTLS, and inspect protocol, cipher, certificate trust, hostname coverage, and expiry across IPv4 and IPv6.

MailDNS follows only this domain's public MX records on port 25. It sends EHLO and STARTTLS, but never MAIL FROM, RCPT TO, or message data.