The solution I use is:
These tools make sending and receiving encrypted and digitally signed email messages easy.
What Mr. Bernier details in this article would probably be best implemented by an IT staff for a corporations in house use. Most email clients have the ability to sign and encrypt using SSL certificates. Once the IT staff created the certificates there would be little configuration for the user. And then all correspondence would have a good degree of security; as opposed to having to create a bloated word document, and using a weaker encryption to send a simple message.