Hi Khürt, 

I may be being a little dumb, but it seems that when you set your mail account to encrypt, it is encrypting it with your own certificate rather than that of the recipient. Surely this means they need to have your private key too, which renders the whole public/private key thing a bit useless?

SMIME on OsX works perfectly, but I have a feeling someone hadn't eaten all their weetabix before the coded it for iOS5! Hoping you can prove me wrong...