[Exim] cyrus delivery without a local account

Hi All,

I am using Exim with Cyrus IMAP. I would like to set up IMAP boxes that
have no associated user account. If I try to send mail throught the
standard setup then the local delivery complains if there is no user. From
readng the docs it's clear I need to use something other than local
delivery but I'm not sure what to do.

I also would like some addresses (like orders@???) to go to a
"public" IMAP box which requires a slightly different delevery command than
for user boxes. How can I provide an alternate delivery technique for
specific names?

Please point me at any docs that may help me understand this all. I've
tried to get some clues by reading the exim spec but it assumes you are
familiar with UNIX mail habits already. Being a UNIX newbie I'm kinda
lost.

Thanks,

David Aue
Nirvis Systems