Encrypting Email Messages in Microsoft Outlook 2007
Email messages are relatively easy for other people to intercept or read. You can avoid this by encrypting your messages so that only the recipient of the message can read it.
To encrypt your message you need to have a copy of the digital certificate of the intended recipient. When you receive a signed email, you can save the certificate of the sender in your Contacts List. You need to create an entry in the Contacts List if you want to send encrypted email to that person. You must also import his or her digital certificate into your Contacts List.
When you receive an email the encrypted icon indicates that the message has been encrypted. This icon appears in the lower right corner (blue padlock) of the address pane. The encryption process is done automatically.
You can encrypt your messages each time you want to encrypt or you can configure your security options so that your messages will be automatically encrypted every time the digital certificate resides in your address book.
When you receive an encrypted message the encrypted icon appears on the email window: