What Does Secure Socket Layer Unified Communications Certificate (SSL UCC) Mean?
Secure Socket Layer unified communications certificates (SSL UCC) are a type of SSL certificate developed for use with the Microsoft Office Server 2007 and Microsoft Exchange 2007 products. The only difference it has with a regular SSL certificate is the Subject Alternative Name (SAN) field, which can contain any number of domain or common names that enable the certificate to work with those listed (domain) names.
Techopedia Explains Secure Socket Layer Unified Communications Certificate (SSL UCC)
Secure Socket Layer unified communications certificates are a single solution that allow SSL encryption for many domain names at once. It can provide great cost savings and it is also required for certain features in Microsoft Exchange, Office Communications Server 2007 and Live Communications Server to work.
But without any of Microsoft’s servers, the UC certificates can still be used to secure multiple website domain and sub-domain names, which offers great cost savings and ease of administration compared to securing a different certificate for each domain name and IP address. UC certificates are compatible with shared hosting, however, the sites would appear connected since the "Issued To" site seal and certificate only indicates the primary domain name.