SMTP Tester
FreeEnter a public SMTP hostname and port to test connectivity, read the server banner and check STARTTLS support when available.
Related tools
Other utilities you may need.
How to use SMTP Tester
Enter a hostname and port. The server opens a short TCP session, reads the banner and optionally negotiates STARTTLS.
Understanding the results
A successful connect shows the banner and whether STARTTLS negotiation is available. Connectivity does not prove the server will accept your mail.
Limitations
- Private and loopback targets are blocked.
- This test does not authenticate or send mail.
Privacy note
Only the hostname and port you enter are used for the connectivity test.
Frequently asked questions
Which SMTP ports can I test?
Common ports such as 25, 465 and 587 can be tested when the host is publicly reachable.
What is STARTTLS?
STARTTLS upgrades a plain SMTP connection to TLS after the initial handshake.
Why might a reachable server still reject mail?
Authentication, relay policy, reputation and recipient rules can reject mail even when TCP connects.
Do I need an account?
No account is required for free tools on this site.