[Dovecot] MS Exchange IMAP Proxy

I need to make the IMAP interface of an Exchange 2000 server available
on the net, however I would like to give it a little protection, and
believe Dovecot's IMAP proxy might be appropriate.

Does anybody have a *really simple* config that would allow IMAP
pass-through to a single Exchange server?

The examples I've seen all assume some sort of load balancing, which
isn't an issue here, so I'd like to eliminate the need for an
unnecessary database server.

Does Dovecot do any cleanup of the IMAP commands that would be useful
in protecting Exchange (from this,
http://www.cvedetails.com/cve/CVE-2007-0221/ for example), or am I
barking up the wrong tree?

If Dovecot isn't helpful for this, can anybody point me to a better resource?

Thanks!

Terry