It would seem the best method to negate this intrusion would be to utilize tools already in existence, PGP being the most obvious. To date though, there is no working beta (that I'm aware of) of a mobile solution in the thunderbird/openPGP vein. I understand the inherent vulnerability of having your private keys on a mobile device, but is anyone working in this space? Is it possible within the confines of the iPhone, Blackberry, etc. mail client? I know personally I would pay quite a bit for an app that mimics the thunderbird/openPGP integration on a mobile device.