Thank you.

The only easy way I know of, is to activate Power Saving mode. Of course, that's not a good solution in your case as Power Saving also causes disconnecting from WLAN after awhile.

So unfortunately I don't know. There might be some Custom Action that might do the trick, but I don't remember seeing such.

In your case, I think it would be enough if you could automatically modify Settings - Notifications - Mail to set it off. But it doesn't seem to be a value that is set in gconf, so I have no idea where that could be modified.