This was suggested to me and it looks like a reasonable tool, though i haven't tried it myself. Basically it's a wrapper around OpenPGP which is designed to be easier to use and integrate better with MS Outlook. I don't use Outlook so i'm not sure it's right for me, but might be a reasonable solution for some. Comes in free and pay versions.
- cGeep Free is a free software made available to all for easy encryption of emails and files alike.
- cGeep Pro is the essential extension of cGeep for a professional use.
- Encrypt your files in 1 click - Integrated to Windows 2000/XP/Vista, cGeep allows you to encrypt your documents and folders in 1 click.
- Encrypt your emails in 1 click - To send an encrypted email, 1 click is enough too! And it works with your usual email client (Outlook Express, Thunderbird, Mozilla, Netscape, Eudora...and even Lotus Notes)!
- On top of that, cGeep ships with cGeep Companion for Outlook Office, a plug-in which offers total integration in the workflow of Outlook Office users.
- In all cases, you keep using your regular email address to send and receive secure encrypted messages. cGeep integrates perfectly in your environment, without changing a thing to your work habits.
- Security and compatibility with OpenPgp - cGeep uses OpenPGP which has been an Internet standard for years. This guarantees not only a strong level of security but also a complete compatibility with other software like PGP.
- Automatic key directory - The free centralised web directory of cGeep users allows for automatic public key retrieval whenever you add a new correspondent - no more lousy search and secret exchange!
- Easy to install and use! - To use cGeep doesn't require any special computer skills or PhD education in cryptography. The software installation is seamless and automated (Windows 2000/XP/Vista) and generates your key pair in a snap.