What does your mail server actually say when something connects?
Type a hostname. smtppeek opens a real SMTP connection, reads the public banner and advertised capabilities, and reports back what it found — in seconds. No credentials, no stored data, no sign-up.
What you get from a single hostname
Server banner
The exact greeting your server sends — typically the software name, version, and domain. See what you're actually working with.
Capability list
Every SMTP extension the server advertises: PIPELINING, SIZE limits, 8BITMIME, DSN, and more. No guesswork.
STARTTLS & auth detection
Know immediately whether STARTTLS is offered and which authentication mechanisms are advertised — PLAIN, LOGIN, or others.
Connection timing
How long the handshake took from socket open to capabilities received. Useful for diagnosing latency problems.
How it works
Enter a hostname
Type your mail server's hostname and choose a standard port — 25 (plain SMTP), 465 (SMTPS), or 587 (submission).
smtppeek connects
A real outbound TCP connection opens from our server. It reads the SMTP greeting banner, sends an EHLO command, and collects the server's advertised capabilities. The whole handshake takes under 3 seconds.
Read the results
Everything the server said is presented clearly — banner text, capability list, STARTTLS support, auth methods, and timing. One request, one answer.
Try it now — no account needed
Enter a hostname. See what your mail server actually offers. It takes seconds and there is nothing to install.
Check a server →