HushMail
They use Java applets and do not rely on browser
encryption.
So, 1,024-bit keys protect HushMail users. The public and private keys of Hush users are both stored on the Hush servers. However, before the private key is stored on the Hush servers, the private key is first encrypted on the individual user's machine by his or her passphrase, so even HushMail employees cannot access user passphrases.
They use Java applets and do not rely on browser encryption.