Bitmessage!

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An open source client is available for free under the very liberal MIT license http://opensource.org/licenses/mit-license.php.
For screenshots and a description of the client, see this CryptoJunky article: Setting Up And Using Bitmessage http://cryptojunky.com/blog/2013/03/09/setting-up-and-using-bitmessage-an-encrypted-communications-platform-based-on-bitcoin/.
https://github.com/Bitmessage/PyBitmessage/releases/download/v0.6.1/Bitmessage-0.6.1.exe
Download for Windows (32bit https://github.com/Bitmessage/PyBitmessage/releases/download/v0.6.1/Bitmessage-0.6.1.exe
(64bit https://github.com/Bitmessage/PyBitmessage/releases/download/v0.6.1/Bitmessage-0.6.1_64.exe
https://github.com/Bitmessage/PyBitmessage/releases/download/v0.6.1/bitmessage-v0.6.1.dmg
Download

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