SMTP STARTTLS Checker
Check STARTTLS support, MTA-STS policy, and TLS reporting for a mail domain. Enter the email domain (not the MX hostname).
Email Domain
About This Check
Full STARTTLS verification requires a direct TCP connection to port 25/587, which is not possible from a browser or edge function. This tool uses DNS-based analysis: MX records, TLSRPT records, and MTA-STS policy to infer TLS support. For a complete probe, use tools like MXToolbox or STARTTLS Everywhere.