What is a Multi-Domain SSL certificate?
A Multi-Domain SSL certificate can secure your main domain along with several SANs (Subject Alternative Names) domain names in one certificate.
Multi-Domain certificates are often used for Unified Communications (UC) to secure Microsoft Exchange 2010 Server, Office Communications Server 2007 or Mobile Device Manager.
For example, you can secure all these domains with a single SAN certificate:
Multi-Domain SSL certificates do not require several dedicated IP addresses for your host names.