See list of outbound email

I have checked my Exchange 5.5 server with some of the blacklisting sites to be sure that relaying is not possible on my server. Yet, I see messages come in that say emails sent by a non-existant account on my server where non-deliverable.

I know that someone could be faking in my return address, but how can I check outbound emails to see if they actually were sent from my server. On the desktop (using Outlook) I can look in the “sent items” folder to see what I have sent. Is there a similar thing in Exchange so that I can see a list of all outbound emails?

Thanks,
Don