Tools
Check SMTP TLS for a domain or mail host
Connects to a domain's mail servers and reports implicit TLS or STARTTLS support, certificate validity, and the TLS version negotiated. Defaults to port 25.
Mail server results
| Mail server | TLS mode | TLS version | Cipher | Certificate | Valid until |
|---|
What this check covers
SMTP can use implicit TLS, which encrypts the connection immediately, or STARTTLS, which upgrades an existing plaintext connection. Both protect mail in transit when successfully negotiated.
- TLS support
- Whether each reachable mail server negotiates implicit TLS or advertises STARTTLS and completes the handshake.
- Certificate trust
- Whether the certificate is trusted, unexpired, and issued for the hostname being tested.
- Negotiated TLS
- Reports the TLS protocol (and cipher) negotiated during the live SMTP connection.