Is the source code available for SecExMail ?
The source code for the core cryptographic components of SecExMail is freely available on the internet.
At the time of writing the Twofish homepage can be found at http://www.counterpane.com/twofish.html.
At the time of writing, the ISAAC home page can be found at http://burtleburtle.net/bob/rand/isaacafa.html.
SecExMail contains cryptographic software from the OpenSSL project at www.openssl.org