Well, that depends on how critical the information is you're sending. Ever considered FedEx? If not, pgp is quite a standard right now for public key encryption, you could also take a look into ibe here http://crypto.stanford.edu/ibe/, looks like a nice alternative to pgp. Even if someone was intended on reading your messages, they would have to go through a lot of work to do this. Again, REALLy confidential information shouldn't be sent via e-mail imho,
