As a kid I used to write messages with lemon juice and when the juice dried I had a secret message (or so I thought) that was viewable when held up to the light.
Of course these child hood secret messages only work in the mind of a child, but not the corporate shield of real business. For your communications between your employees, your partners or your clients you need to ensure that each email message that needs to be secure, is secure.
Published with permission from TechAdvisory.org. Source.