Don’t Reject Unknown Reciepients

My server gets alot of messages addressed to non-existant users (it's presumably spam.) Rather than have Postfix reject it, though, I'd like for the messages to be accepted & delivered to a specific user. This way I can sift through it and report the spam. I've been searching both this site and the internet in general looking for info on how to have Postfix not reject unknown recipients & instead deliver them to somewhere else. In my searches I've come across Postfix's "luser_relay" command, but it's not made a bit of difference (i.e., mail still rejected.) Has anyone does this themselves? Anyone care to share info on how to get Postfix to do this??? Another thing to mention is that I have some virtual domains created (using the info at https://www.afp548.com/articles/Panther/postfixvirtual.html.)