Certificates that use Subject Alternative Names (SAN) are powerful tools that are available to secure multiple domain names inexpensively and efficiently. Certificates that use SAN are called Unified Communications certificates, and are commonly used with Microsoft Exchange Server 2007, Microsoft Exchange Server 2010, and Microsoft Communications Server. The purpose of a certificate with SAN is the same as that of other certificates, but instead of purchasing individual certificates for each domain name, you can add domain names in the SAN field, so they can share the same certificate. This saves an organization the cost of purchasing individual certificates and time spent managing multiple certificates.