Hi Joe,
To differentiate which user sent the message from the alias, Domain Administrators can allow users to customize their signature mapping per alias. Otherwise, they can force a specific signature to be displayed and use the Account Profile variables to pull the signature details from the user's account.
However, for cases where the signature is NOT included on a message, I do feel it would be useful to include the sending user's information in the logs. I'm going to change this thread from a Question to a Proposed Idea to facilitate tracking on that addition. Please keep in mind, though, that if the user's address is added to the logs (rather than just showing the alias address), that information would be available to System Admins only.
Andrea Free
SmarterTools Inc.
877-357-6278
www.smartertools.com