qmail:forwarding outgoing mail to a local account

Allright, this may sound bitchy, but I need to keep track of all the outgoing messages of my network. I've seen that there is no option for forwarding outgoing mail, so I'm asking myself if there would be a way to do that (the mail must be sent to the delivery address also, obviously).

I'd even do with a tool to copy all the outgoing queue to a folder, then I would develop a php script to explore the messages or something.

Thanks in advance.