What does your mail server actually say?
When email stops working, the useful question is what your mail server says to a client that connects to it. MailProbe opens a real SMTP connection, reads the banner, checks STARTTLS, and lists every advertised authentication mechanism — no terminal required.
How it works
1
Enter a hostname — the mail server you want to test, e.g.
mx.example.com.
2
Choose a port — 25 (SMTP), 587 (Submission), or 465 (SMTPS).
3
MailProbe connects — opens a raw TCP socket, reads the server greeting, sends EHLO, and parses the capability list.
4
See the results — banner text, STARTTLS support, auth mechanisms, and handshake latency. The server's own protocol text, verbatim.
$ mailprobe mx.example.com 587
Connecting to mx.example.com:587...
220 mx.example.com ESMTP Postfix (Ubuntu)
EHLO mailprobe
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
Latency: 87 ms
What you get
Greeting banner
— the server identifies itself. See the exact software and version it advertises on connect.
STARTTLS support
— detects whether the server offers STARTTLS and shows the encrypted capability set after upgrade.
Auth mechanisms
— lists every advertised SASL mechanism (PLAIN, LOGIN, CRAM-MD5, etc.). No credentials sent.
Handshake latency
— measures how long the server took to respond, from connect to EHLO response.
No credentials stored
— MailProbe reads public banners only. It never sends AUTH, never stores results.
Why a real connection?
DNS lookups and port scans can guess whether a server exists, but only a real SMTP handshake tells you what the server actually supports. MailProbe does what an admin would do by hand with telnet or openssl s_client — it just saves you the typing.
The tool connects on your behalf from a dedicated server. This is necessary because browsers cannot open raw TCP sockets, and SMTP is a line-based protocol, not HTTP.
What this is not
- Not a mail sender — it never sends email.
- Not a port scanner — only connects to the hostname you type, on standard mail ports.
- Not a login tool — it reads public banners, never credentials.
- Not a monitoring service — it runs when you click Check, and only then.