iPhone Mail & Proxy Servers

At work, I'm fortunate enough to be able to access our wireless network. I have the connection configured to use a proxy server which is required for all traffic passing through our firewall. The iPhone web browser works just fine access pages with no problems at all.

However, the Mail application is unable to reach my mail server (I use .Mac). I can get to the server just fine using the iPhone web browser so I know the connection is working and the server is responding; however, attempting to access it with the mail application results in the error message, "The connection to the server 'mail.mac.com' failed."

I'm guessing this is because the Mail application is trying to access the server directly, but it actually needs to route the connection through my proxy server. Is there some way to configure the Mail application to make this work?