Open Terminal

SMTP Test

Available

Connect to a public mail server, read its SMTP banner and EHLO capabilities and check STARTTLS — without sending any email.

SMTP Test

Mail server, or a domain to test via its MX

SMTP port

Open in terminal
Try:

How it works

A sandboxed worker opens a single SMTP connection, records the banner and EHLO response, attempts STARTTLS to report the TLS version and certificate, then closes with QUIT.

Safeguards & responsible use

  • Connects only to public IP addresses — re-checked after DNS resolution — on SMTP ports 25, 465 and 587.
  • Strict connect and per-command timeouts, one connection per test and limited concurrency per client.
  • Read-only conversation (banner, EHLO, STARTTLS, QUIT): no message is sent and relaying is never attempted.
  • No authentication: NetTools never asks for mailbox passwords or other credentials.

Frequently asked questions

Will this send an email?

No. The test stops after EHLO and STARTTLS and disconnects with QUIT. No message, sender or recipient is ever transmitted.

Do I need to enter my email password?

No — and you never should. NetTools does not test authentication and will never ask for mailbox credentials.