Secure email?

[Normen Nomesco <dis-list () rebelbase com>]

I am writing a security paper on protection of intellectual assets in email via a layered approach to
secure communication channels when dealing with client to server, and server to server, mail exchange.

I am including how to use TLS (formerly ssl) to encrypt between mail servers, client to mail server options, 
secure password authentication, IPSEC <for wireless communication> and ssh-2 port forwarding.

Any suggestions for articles, or experiences would be appreciated
ill probably post my first revision of my paper  later tonight to anyone that is interested.

Ian