A Unified Communications Certificate (UCC) is an SSL certificate that secures multiple domain names and multiple host names within a domain name. A UCC lets you secure a primary domain name and up to 99 additional Subject Alternative Names (SANs) in a single certificate. UCCs are ideal for Microsoft® Exchange Server 2007, Exchange Server 2010, and Microsoft Live® Communications Server.
UCCs are compatible with shared hosting. However, the Website seal and certificate "Issued To" information will only list the primary domain name. Please note that any secondary hosting accounts will be listed in the certificate as well, so if you do not want Websites to appear 'connected' to each other, you should not use this type of certificate.
You cannot upgrade a UCC to include more names. If you bought the UCC with up to five domain names, you need to purchase a new certificate to add another domain name.