With a lot of modern routers (ISA, Watchguard, etc..) we can put some proxy actions for publishing services. What's the advantage? We can monitor the entire conversation between the client and our web server. Just like client outbound proxies, however, there can be some mishaps. One good example is how a WebDav server can behave under a http proxy, you may get mixed results. OWA (Outlook Web Access) is a WebDav server for IE clients, and sometimes you may get errors like not being able to see your inbox, but you can see your folders just fine, or Active Sync just not working at all.
First lets look at the OWA error. In my example, I'm using a Watchgaurd XTM firewall with a HTTPS proxy to publish OWA. With the Proxy's default values, we can log into OWA, but showing anything in the inbox keeps a "loading…" message. In order to make the inbox come up, we need to add a simple checkbox:
Which bypasses proxy actions to allow WEBdav.
Next, lets look at ActiveSync. ActiveSync will just not work with watch guard's default HTTPS proxy. The best way to diagnose it to try to go to the ActiveSync web page:
With this, we need to allow the "Option" method in the HTTP protocol: