For starters, the couple could have used stress-tested PGP (Pretty Good Privacy) for point-to-point encrypted email which involves installing a separate piece of client software and the exchanging of public keys.

FORBES: The General, The Biographer, And Unencrypted Email

The U.S. government today announced that it would permit Network Associates Inc. a license allowing it to ship its 128-bit PGP (Pretty Good Privacy) product to a large number of countries, excluding countries such as Iraq and Cuba.

CNN: Zero-Knowledge launches anonymous access