Find logs of emails sent from an Exchange Relay

We've got a membership-based Web app that runs from an Internet-facing Windows 2003 server. That server is setup as a "relay" through our Exchange 2010 server. SOME, not all, users are reporting that emails sent from the web server aren't being received.

I'm wondering if there's a way to view logs of emails sent by the relay. I can't seem to find any utility in the Exchange Management Console; nor am I finding any email-related logs in the event viewer of the aforementioned web server.

Any insight would be greatly appreciated!