Q: Is it possible to use an HTTP proxy over a cellular 3G connection? I know it works (through proxy) when connected over Wi-Fi. It is something required by our security policy for all devices with corporate data
A: It is possible to do change your 3G configuration, but to do this you will need to download the iPhone Configuration Utility from Apple’s iPhone Enterprise Support Page and build an iPhone configuration profile with the alternate settings and then upload it to your iPhone.
The iPhone Configuration Utility allows you to configure a number of options, including password policies, Wi-Fi and VPN configurations, pre-defined e-mail and calendar accounts, and install SSL certificates for other services. The 3G configuration settings can be found on the “Advanced” section at the bottom of this list.
Once you’ve created and built a configuration profile, you can either upload it directly to your iPhone over a USB connection or you can save it as a “mobileconfig” file and e-mail it to your iPhone and install it from there.