Email Help

[dell4242]

I need to be able to check to see if a individual sent emails to accounts on a plesk server.I am hitting a brick wall since It doesn't look like plesk has any filtering capability built in. Is there a way to do this? All I really need to know is if and when an email is sent. I wouldn't mind doing a grep on a file daily to determine if the user has sent anything. Is there a way to make qmail to do verbose logging enough to get this information?
Any help would be greatly appreciated.