The server is talking to me. (click for larger image)
The first line tells you the server is talking to you. If you don't get this, you know the server is not talking to you, and you can now have a better feel for the problem.
I further tested the responsiveness of the server by giving the HELO command with an email address (you'll want to use yours). The HELO command simply asks the server to confirm a session. QUIT, of course, terminates the connection.
What this tells us
At this point, we know the server's up and is talking. If you can't get a response from the telnet, but you can ping the server, you'll know the server machine is running, but that the mail server itself isn't -- or at least, isn't talking to you.
This is a lot more useful data and will help you work with your ISP to further diagnose the problem.