Q. I don't want to expose my windows machine to the world and much rather run Outlook Web Access (OWA) through an Apache Rewrite/ProxyPass - how can I do that?

A. We haven't tested MS Exchange 2007, but it worked with 2003. It is not something that is highly recommended, but it has its advantages. First of all, you are right - the windows system is blocked and only exchange web is accessible. Second, you have 2 servers - Linux and Windows. With ProxyPass, you can host windows applications (ie. .Net, mssql, etc.) and with direct access - you have Apache, MySQL, PHP, python, perl, etc.

<VirtualHost *:80>
DocumentRoot /www/docs/exchange
ServerName mail.example.com
ServerAlias www.mail.example.com

SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1

ProxyPreserveHost On

#OWA % character in email subject fix
RewriteEngine On
RewriteMap percentsubject int:escape
RewriteCond ^/exchange/.*\%.*$
RewriteRule (/exchange/.*) ${percentsubject:} [P]                      

ProxyPass /rpc http://192.168.1.10/rpc/
ProxyPassReverse /rpc https://192.168.1.10/rpc/
ProxyPass /exchange http://192.168.1.10/exchange/
ProxyPassReverse /exchange http://192.168.1.10/exchange/
ProxyPass /exchweb http://192.168.1.10/exchweb/
ProxyPassReverse /exchweb http://192.168.1.10/exchweb/
ProxyPass /public http://192.168.1.10/public/
ProxyPassReverse /public http://192.168.1.10/public/
ProxyPass /iisadmpwd http://192.168.1.10/iisadmpwd/
ProxyPassReverse /iisadmpwd http://192.168.1.10/iisadmpwd/
ProxyPass /exchange-oma http://192.168.1.10/exchange-oma/
ProxyPassReverse /exchange-oma http://192.168.1.10/exchange-oma/
ProxyPass /Microsoft-Server-ActiveSync http://192.168.1.10/Microsoft-Server-ActiveSync/
ProxyPassReverse /Microsoft-Server-ActiveSync http://192.168.1.10/Microsoft-Server-ActiveSync/

CacheDisable *

</VirtualHost>

You should be able to just copy paste this code, replace mail.example.com with whatever your domain is, replace IP and restart Apache.

We've got a few errors in the logs:

proxy: Max-Forwards has reached zero - proxy loop? returned by

Most of them was from Spam with funny characters in the subject, so ignored those. The emails that returned this error eventually opened.