I'm not trying to connect to it so I can send an email through the server. What I was trying to understand how to do was to deliver and email to it. For example, if I build an SMTP server and a client which connects to my that SMTP server and I want to send an email to email@example.com (where mycompany.com is hosted on the Exchange server), how would the SMTP server I created connect to the Exchange server in order to deliver the email? Doesn't the Exchange server have to allow some sort of connection from outside the intranet in order to receive emails from other domains (gmail, yahoo, etc.)?