Encrypting Your Email Messages in Outlook 2003
Encrypting your email messages ensures that the message is only visible to you and the recipient. In order to enable encrypted email you must store a copy of the recipient's certificate in your Contacts List. Once you have configured your Toolbar to include the Sign and Encrypt buttons you can encrypt messages by simply clicking the encrypt button as shown below.
Encrypted emails are distinguished by the blue padlock icon that appears in the lower-right-corner of the address pane as shown below.
You can encrypt your messages on a case-by-case basis by clicking the Encryption button in the Toolbar. Alternatively, you can configure your security options so that your messages will be automatically encrypted every time you communicate with a user with whom you have exchanged and stored (in your address book) certificates.