testare un servizio SMTP, con telnet

come faccio a sapere se un smtp funziona ?
ecco la risposta in 10 semplici mosse:

1. At a command prompt, type Telnet and press ENTER.
2. At the telnet prompt, type and press ENTER, and then type open localhost 25 and press ENTER.
   The output resembles the following:
   220 computername.microsoft.com ESMTP Server (Microsoft Exchange Internet Mail Service 5.5.2651.58) ready
3. Type helo me and press ENTER.
   The output resembles the following:
   250 OK
4. Type mail from:email@domain.com and press ENTER.
   The output resembles the following:
   250 OK - mail from <email@domain.com>
5. Type rcpt to:youremail@yourdomain.com and press ENTER.
   The output resembles the following:
   250 OK - Recipient <youremail@yourdomain.com>
6. Type Data and press ENTER.
   The output resembles the following:
   354 Send data. End with CRLF.CRLF
7. Type Subject:This is a test and press ENTER twice.
8. Type Testing and press ENTER.
9. Press ENTER, type a period (.), and press ENTER.
   The output resembles the following:
   250 OK
10. Type quit and press ENTER.
    The output resembles the following:
    221 Closing Port / Mail queued for delivery