Mail to nowhere

The next phase of my testing procedure involves the simple act of delivering mail to my test box. When I send a message to either a valid or relayed user at my remote machine's address, it never gets there. I know this virtually for sure because I'm tailing /var/log/maillog and nothing new has been added for the past hour. I'm thinking eventually my ISP will send the message back to me as undeliverable, and in that bounced message there may be some information about why it was undeliverable, but maybe someone has a thought as to why I'm not even seeing anything attempt to connect?