[NTLUG:Discuss] Apache as a reverse proxy?

[Daniel Hauck]

http://www.wlug.org.nz/ApacheReverseProxy

The article above tells how to set up a web proxy to an Exchange
server's web mail interface.  But it also states that this creates an
open proxy for other things and is potentially dangerous.

So I'd like to know if there's a way to set up something like this
without the dangerous side-effects?  I don't want *ANY* public internet
facing connections directly to my Microsoft servers.  At the moment, the
last public facing interfaces are our web based email and pop3 services.
 So I'm looking for means put a layer between the Microsoft servers and
the public internet.

It wasn't too long ago that our SMTP server was partially compromised.
I say partially because even though it was "accepting" mail for
retransmission, it wasn't actually sending any.  My response was to
close SMTP and create my own SMTP server from Linux.  Worked nicely.  So
I'd like to do the same for POP3 and OWA (Outlook Web Access) services
as well... I feel like it's only a matter of time before spammers find
ways to utilize these services as a means of spreading their evil and I
really don't want to wait until that happens.