All tools
TLS & SSL
SMTP TLS Checker
Probe a mail server's STARTTLS support, negotiated TLS version, cipher suite, and certificate chain validity.
This tool is being wired up. The analyzer ships in the next build phase.
About this check
Probe STARTTLS, TLS version, ciphers, and cert validity.
Frequently asked questions
- What does the SMTP TLS Checker actually check?
- Probe STARTTLS, TLS version, ciphers, and cert validity.
- Is this really free?
- Yes. Every on.bo tool is free, no signup required, no rate-limit tricks.
- Do you store the data I check?
- We log minimal metadata to keep the service healthy. Lookups themselves are not retained beyond short-term caching.