Try: HushMail free or premium web-based encrypted web-mail accounts.
or Hushmail Private Label (or Hush Identity for smaller businesses to manage their own e-mail accounts with their domain name) "is a Web-based, totally secure, email outsourcing solution. With Private Label, you can offer visitors to your site the convenience of Web-based email protected by Hush's encryption technology."

Please note that this page does not address protecting e-mail (or other files) already on your system from being read or copied. This page addresses encryption and digital signing of e-mail messages and attachments to be sent to others.

Yahoo's Security and Encryption category

Contents: Purposes of encryption/security: Comparison of PGP and S/MIME: Other secure e-mail systems:

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