Multi-Domain SSL certificates, also known as Unified Communication Certificates (UCC) and Subject Alternative Name (SAN). All of them solve the requirement of protecting multiple domains and sub-domains. They are very popular for companies who run various local websites. CDN (Content Delivery Networks) use them to protect all their customers.
The modern SAN SSL supports up to 250 items, where each item can be used for domain or sub-domain. Some products like Multi-Domain Wildcard SSL certificates may support *.domain.tld (Wildcard domains) as SAN item.
SAN certs are compatible with MS and other exchange servers. It is very comfortable to use them, as you would have just one CSR and Private key, that makes management quite simple.
