Process sendmail spool by postfix

This week, we had big troubles on our mailserver at VTK. The big ugly devil was sendmail. He stopped delivering mails to local users. After trying to fix it, wich didn't make it work, Lennert and Ikke installed postfix on the machine. Everything is working now, but there's one big issue: sendmail still had 240 messages in /var/spool/mqueue, wich he had to deliver but never did. Now, I want postfix to deliver these. I already did some research, but all I found was "put the files in /var/spool/mqueue.in" wich is a Q for postfix on some configurations. We don't have such a configuration. We have /var/spool/postfix/incoming (and so on) with lots of folders (1,2,3...,A,B,...) in it with the same kind of subfolders in. I don't know where to put those files in now.

If someone nows how to make postfix handle these messages, or how to make sendmail just send these messages to some smtp-server (but not handle the incoming ones), please let me know. Thanks.