MS: Test the SMTP Service in Exchange Using Telnet

You can use TELNET to test your SMTP service. SMTP uses port number 25, so in order to use telnet to open an SMTP session with the Exchange server we use the command:

TELNET localhost 25

If the connection is successful, we should see a banner and a command line interface:

220 mailtest.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.1830 ready at Thu, 25 Jan 2007 12:03:43 +0100
helo
250 mailtest.local Hello [127.0.0.1]
mail from: admin@mailtest.local
250 2.1.0 admin@mailtest.local....Sender OK
rcpt to: guillermo@mailtest.local
250 2.1.5 guillermo@mailtest.local
data
354 Start mail input; end with .
subject: test
This is a test
.
250 2.6.0 <CAMMSVRMMFRaqbC8wSA00000002@mailtest.local>Queued mail for delivery
quit
221 2.0.0 cammdomain.dev
Service closing transmission channel
Connection to host lost.