>>8
Ideally if you know who you gonna send the data and can meet him in person, you can use one time pod encryption.
Give him a staple of labeled cd's with random data, keep yourself a copy of every cd. Choose one cd, read the label, xor the data with the cd, destroy the cd and send the encrypted data over with the label. He chooses the right cd by reading the label from the email and compare it to the label of the cd, decrypt the data with xor and destroys the cd.
If you run out of cd's, you can meet again.