Using iPad in school with proxy server!
One of the schools I support has got some iPads in school now. The school uses a Sophos Web Appliance for its internet filtering.
The iPads are setup to go through the proxy server and they work for web browsing just fine. However, for some reason when you try and use the native mail app, it doesn't seem to get through to the internet. We have tried for a while now to figure this one out and even had Sophos on the case but can't seem to get it working.
iPad Mail App through Proxy
You have to set up firewall rules for the mail app to work. We had to set up an SMTP rule and add all of the ports for all of the different mail providers. Some other apps don't support proxies that require authentication regardless of what you set up in the proxy settings on the device.