What does "encrypt all outgoing email" really mean? I have a Samsung Galaxy Stardust with Android 4.3.  In the email app, under security options, there is an option that says "encrypt all outgoing email".  But my understanding of S/MIME is that in order to encrypt e-mail to someone, I have to have their public key.  So it seems like this option can't really do what it says it does.
It actually gets the public key of the receiver before sending the email. So yes, it could do what it says.