You want to enroll a user so she can use S/MIME with Exchange Server 2003.
Install or gain access to a certificate authority (CA) that can issue certificates to your users. Chapter 6 of the Exchange Server 2003 Message Security Guide covers this process in detail, as does the Windows Certificate Services documentation included with both Windows 2000 and Windows Server 2003.
Log on to the computer on which you want to enroll in advanced security.
Launch Outlook using the profile that you want to request a certificate.
Request a certificate from your CA. For Windows Certificate Services installations:
Open a browser window and go to http://<CAServerName>/certsrv.
Click Request a certificate.
Click User certificate.
If Internet Explorer prompts you to confirm your request, click Yes.
Depending on how the CA is configured, your request may be automatically approved, or an administrator may have to approve it. If the request is automatically approved, you'll see a link labeled Install this certificate. Click it.
If Internet Explorer prompts you to confirm that you want to add this certificate to the local computer, click Yes.
Switch to Outlook. From the menu, select Tools→ Options. The Options dialog will appear.
Click the Security tab and click the Settings button. The Change Security Settings dialog will appear as shown in Figure 10-2.
Use the Choose buttons in the Certificates ...