[exim] Using IMAP folders as quarantine

Hi,
Exim is our gateway. It gets 98% of spam and all viruses. In the past
though we have been letting through that 2% of spam plus other
undesirable mail such as newsletters, etc to another windows computer
where everything is further quarantined for admin perusal. We would like
to rid ourselves of the windows box. The idea is to drop the mail into
IMAP folders (a single account) on the gateway for admin to review
befire sending, but I have several issues that I'm hoping people here
with experience can help with.

1) Some mail with cc'd addresses is being duplicated in local delivery
as many times as there are addresses from our domain.

2) If the mail is good, how do we "release it" (using Mozilla
Thunderbird and Courier-imap's Outbox feature) without Exim trying to
send to all of the cc'd addresses not in our domain? Does anyone know of
a better way to do this using (or not using) IMAP. I've briefly looked
at Mailscanner but I'm not clear on the admin interface for releasing
mail from multiple queues.

I understand that these aren't really nitty gritty Exim questions,
except that whatever solution I find needs to work with Exim because
that part of the equation isn't open to question.

Thanks,
Craig