Internet Standards Clients (POP3 and IMAP4)

Exchange supports Internet standards e-mail protocols, POP3 and IMAP4. S/MIME capabilities have been available in a number of e-mail clients that support Internet standards for some time. Any Internet standards client that supports S/MIME version 3 can be integrated seamlessly into an Exchange 2003-based message security system. As with Outlook, the only requirement for Exchange is that there is connectivity between the e-mail client and the Exchange server. With connectivity, you can use the e-mail client's support for PKI to integrate the e-mail client into a public or private PKI. Internet standards e-mail clients from Microsoft that support S/MIME version 3 include Outlook 2000 SR-1 or later and Outlook Express 5.5 or later.

When implementing Internet standards clients, consider Active Directory integration for digital certificates. Although the choice of directory is specific to a particular PKI, because Active Directory is used as the PKI directory for several Microsoft e-mail clients, including Outlook, Outlook Express, and Outlook Web Access with the S/MIME control, you may want to connect other e-mail clients to Active Directory as the PKI directory. Using Active Directory can provide a single repository for storing digital certificates across multiple e-mail clients and simplify management. For information about determining if your e-mail client can integrate with Active Directory and how to implement this task, see the documentation for your specific e-mail client and Active Directory.