I just jumped in on this thread, but I ran the above code
on my localhost, and it connects. So you have sendmail going
on port 25, and is that the port you are trying to connect to?

Output:
zentara@zentara:~/perlplay > ./z9b localhost 25
Connected to localhost:25
220 zentara.zentara.net ESMTP Sendmail 8.11.3/8.11.3/SuSE 
Linux 8.11.1-0.5; Wed, 4 Sep 2002 12:20:34 -0400
250 2.0.0 Queuing for node mydomain.com started
221 2.0.0 zentara.zentara.net closing connection