How can I reduce the mobile data used by the iPhone Mail app? I am on a 200 MB/month plan, and feel that Mail is responsible for most of my mobile data usage, sometimes pushing me over the 200 MB, even if I almost never use the iPhone in places where there is no WiFi. I can either setup the phone:


To use push or pull at a regular interval. In either case, it will sometimes download new mail in the background, while the phone is locked. And this means it will do so over 3G instead of WiFi, even if there is WiFi where I am.
To disable push and and set fetch to "manually". I guess this will reduce my mobile data usage, but I would then have to wait after launching Mail for it to download my mail.


Ideally, I'd like the iPhone to use "push" when over WiFi and "fetch manually" when over 3G, but there doesn't seem to be an option for this.

What would you say is the optimal setup to reduce the use of  mobile data, without going to "fetch manually"?
There is no way to do this in iOS.

For a workaround you could turn off 3G and turn it on when you need it, just before you open up Mail, that way when you are connected to WiFi you will get push, but manually have to get from 3G.

It's not a great situation: I would just increase your data cap, although I know that is not always easy, hence you asking for this workaround.