Well, every once in a while you need to do this. And what was the command again ?? How did that work exactly ?? As my memory is getting overloaded once in a while I decided to post my favorite Link right here, that way I know where it is next time I need it.
http://www.simplescripts.de/smtp-check-port-25-telnet-command.htm
That’s the page I use for a quick look up.
I use swaks (Swiss Army Knife SMTP), a little perl script, to solve this problem.