Open a command line and type 

telnet smtp-server.domain.com 25
An Exchange Server answers with the following output: 
220 mailserver.domain.com Microsoft ESMTP MAIL Service, Version: 5.0.2195.5329 ready at  Fri, 19 Aug 2011 10:39:14 +0200 
Try the following to send an eMail from the command line:    
helo myserver.domain.com 
250 mailserver.domain.com Hello [10.1.11.133] 
mail from:<myname@mydomain.com> 
250 2.1.0 myname@mydomain.com....Sender OK 
rcpt to:<recipientname@mydomain.com> 
250 2.1.5 recipientname@mydomain.com 
data 
354 Start mail input; end with <CRLF>.<CRLF> 
subject: This is a test 
to: recipientname@mydomain.com 
This is body portion of test.
. 
250 2.6.0 <exchange.domain.com> Queued mail for delivery 
quit