[exim] remote courier

Hi All,


I have a server that is heavily overloaded as it does webmail/imap/AV
scanning/spamd for about 400+ users.. This server currently uses
Qmail+courier imap. I am building an exim based server to take the
smtp/antivirus/spamd off of the imap server and another one to handle
purely the webmail. This would mean that I am dropping Qmail on the
existing server and basically turning it into an imap server.
My question is :
how can i configure Exim to deliver to the remote courier Imap server
but still retain the features of exim like bouncing invalid address's
etc.. as we found that we where getting thousands of emails going to
postmaster that where to invalid or expired user's.

Also is there a way in exim to log every message including the content
as they currently have this in qmail.

Many thanks

Simon