Instead of setting up your own certificate server you can purchase certificates from a third-party certification authority (CA). Third-party certificates are often assigned to virtual servers that handle external users because most public CA root certificates are already in the Windows operating system. Because of that, a certificate from a public CA enables users to connect to Communicator Web Access (2007 R2 release) without having receiving repeated security warnings, and without having to download and install a certificate from your organization’s CA.

If you decide to use certificates from a third-party CA, keep in mind that the CA must be able to process certificate requests in the Certificate Management protocol, using the Cryptographic Message Syntax (CMS) Public Key Infrastructure (PKI) format.

For details about how to purchase, download, and install these certificates, you need to contact the CA itself.