openacs doesn't need any specific qmail.rc file - you can set it up however you like - as long as you allow your localhost to relay you should be able to use any email server. I personally use qmail and love it... i recommend installing qmail via the instructions here:
The have an RC script there and explain how to set up Maildir as the default storage type - to summarize (you need to edit /var/qmail/control/defaultdelivery and have it say nothing but "./Maildir/") though i recommend reading life with qmail so you can understand how the other important functions of the qmail mail server. In particular understanding the tcp.smtp.cdb database usage is very important (done via tcpserver).
