The SSL Certificates multi-domain , also known as Unified Communications Certificates (UCC) and Subject Alternative Name (SAN) .
They all solve the requirement of protecting multiple domains and subdomains. They are very popular for companies that manage various local websites. Content Delivery Networks (CDNs) use them to protect all their customers.
The modern SAN SSL supports up to 250 articles, where each article can be used for the domain or subdomain. Some products such as Wildcard Wildcard Multi-Domain SSL certificates may support * .domain.tld (Wildcard domains) as a SAN element.
SAN certificates are compatible with MS and other exchange servers. It is very convenient to use them, as you only have one CSR and one private key, which makes management quite simple.