SMTP Test
Free SMTP Test Tool
Live reachability across ports 25, 465 and 587 — with a real STARTTLS upgrade to read the actual negotiated TLS version and cipher, plus a non-abusive open relay test.
SMTP Test
Reachability, real STARTTLS upgrade, negotiated TLS version/cipher, across ports 25, 465 and 587.
Enter a domain above to run a real, live check.
Capabilities
What it checks
Real TLS negotiation
Actually upgrades the connection via STARTTLS to read the true protocol version and cipher.
All three ports
25 (SMTP), 465 (implicit TLS) and 587 (submission) tested in parallel.
Open relay test
A standard, non-abusive protocol check — no message is ever actually sent.
Why use it
Benefits
- Confirm a mail server enforces modern TLS instead of falling back to plaintext.
- Verify a firewall change didn't accidentally block a required SMTP port.
- Catch a dangerously misconfigured open relay before it's abused for spam.
FAQ
Frequently Asked Questions
No — it reports which AUTH mechanisms the server advertises in its EHLO response, never attempts an actual login with credentials.